diff --git a/Sources/Crypto/AEADs/AES/GCM/AES-GCM.swift b/Sources/Crypto/AEADs/AES/GCM/AES-GCM.swift
index 0070f296f..fecedae73 100644
--- a/Sources/Crypto/AEADs/AES/GCM/AES-GCM.swift
+++ b/Sources/Crypto/AEADs/AES/GCM/AES-GCM.swift
@@ -21,7 +21,11 @@ import Security
 typealias AESGCMImpl = OpenSSLAESGCMImpl
 #endif
 
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension AES {
     /// The Advanced Encryption Standard (AES) Galois Counter Mode (GCM) cipher
diff --git a/Sources/Crypto/AEADs/AES/GCM/BoringSSL/AES-GCM_boring.swift b/Sources/Crypto/AEADs/AES/GCM/BoringSSL/AES-GCM_boring.swift
index 77b1202c0..415846518 100644
--- a/Sources/Crypto/AEADs/AES/GCM/BoringSSL/AES-GCM_boring.swift
+++ b/Sources/Crypto/AEADs/AES/GCM/BoringSSL/AES-GCM_boring.swift
@@ -16,7 +16,11 @@
 #else
 @_implementationOnly import CCryptoBoringSSL
 import CryptoBoringWrapper
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 enum OpenSSLAESGCMImpl {
     @inlinable
diff --git a/Sources/Crypto/AEADs/ChachaPoly/BoringSSL/ChaChaPoly_boring.swift b/Sources/Crypto/AEADs/ChachaPoly/BoringSSL/ChaChaPoly_boring.swift
index 02ff58ea0..7c2efd7f4 100644
--- a/Sources/Crypto/AEADs/ChachaPoly/BoringSSL/ChaChaPoly_boring.swift
+++ b/Sources/Crypto/AEADs/ChachaPoly/BoringSSL/ChaChaPoly_boring.swift
@@ -17,7 +17,11 @@
 @_implementationOnly import CCryptoBoringSSL
 @_implementationOnly import CCryptoBoringSSLShims
 import CryptoBoringWrapper
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension BoringSSLAEAD {
     /// Seal a given message.
diff --git a/Sources/Crypto/AEADs/ChachaPoly/ChaChaPoly.swift b/Sources/Crypto/AEADs/ChachaPoly/ChaChaPoly.swift
index bd24bde3d..fab3b1611 100644
--- a/Sources/Crypto/AEADs/ChachaPoly/ChaChaPoly.swift
+++ b/Sources/Crypto/AEADs/ChachaPoly/ChaChaPoly.swift
@@ -21,7 +21,11 @@ import Security
 typealias ChaChaPolyImpl = OpenSSLChaChaPolyImpl
 #endif
 
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// An implementation of the ChaCha20-Poly1305 cipher.
 public enum ChaChaPoly: Cipher {
diff --git a/Sources/Crypto/AEADs/Cipher.swift b/Sources/Crypto/AEADs/Cipher.swift
index 573b4daea..59b6bdb66 100644
--- a/Sources/Crypto/AEADs/Cipher.swift
+++ b/Sources/Crypto/AEADs/Cipher.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 protocol AEADSealedBox {
     associatedtype Nonce: Sequence
diff --git a/Sources/Crypto/AEADs/Nonces.swift b/Sources/Crypto/AEADs/Nonces.swift
index 184ff3c0b..e62b4f834 100644
--- a/Sources/Crypto/AEADs/Nonces.swift
+++ b/Sources/Crypto/AEADs/Nonces.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 // MARK: - Generated file, do NOT edit
 // any edits of this file WILL be overwritten and thus discarded
 // see section `gyb` in `README` for details.
diff --git a/Sources/Crypto/AEADs/Nonces.swift.gyb b/Sources/Crypto/AEADs/Nonces.swift.gyb
index 19a25bb2a..fe75a01c9 100644
--- a/Sources/Crypto/AEADs/Nonces.swift.gyb
+++ b/Sources/Crypto/AEADs/Nonces.swift.gyb
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 // MARK: - Generated file, do NOT edit
 // any edits of this file WILL be overwritten and thus discarded
 // see section `gyb` in `README` for details.
diff --git a/Sources/Crypto/ASN1/ASN1.swift b/Sources/Crypto/ASN1/ASN1.swift
index a1d4c250e..54d854782 100644
--- a/Sources/Crypto/ASN1/ASN1.swift
+++ b/Sources/Crypto/ASN1/ASN1.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 // This module implements "just enough" ASN.1. Specifically, we implement exactly enough ASN.1 DER parsing to handle
 // the following use-cases:
diff --git a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Any.swift b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Any.swift
index 8bec3361f..df6fa2aaf 100644
--- a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Any.swift	
+++ b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Any.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension ASN1 {
     /// An ASN1 ANY represents...well, anything.
diff --git a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1BitString.swift b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1BitString.swift
index 4f00bf682..212cd499b 100644
--- a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1BitString.swift	
+++ b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1BitString.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension ASN1 {
     /// A bitstring is a representation of...well...some bits.
diff --git a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Boolean.swift b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Boolean.swift
index 43510e916..5a7072167 100644
--- a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Boolean.swift	
+++ b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Boolean.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension Bool: ASN1ImplicitlyTaggable {
     static var defaultIdentifier: ASN1.ASN1Identifier {
diff --git a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Identifier.swift b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Identifier.swift
index 6c98f082f..024783a71 100644
--- a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Identifier.swift	
+++ b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Identifier.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension ASN1 {
     /// An `ASN1Identifier` is a representation of the abstract notion of an ASN.1 identifier. Identifiers have a number of properties that relate to both the specific
diff --git a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Integer.swift b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Integer.swift
index d8101c4e7..c4287eb9e 100644
--- a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Integer.swift	
+++ b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Integer.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// A protocol that represents any internal object that can present itself as an INTEGER, or be parsed from
 /// an INTEGER.
diff --git a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Null.swift b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Null.swift
index 83fb8646f..9017987bf 100644
--- a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Null.swift	
+++ b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Null.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension ASN1 {
     /// An ASN1 NULL represents nothing.
diff --git a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1OctetString.swift b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1OctetString.swift
index f7e1336d6..624d5ae43 100644
--- a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1OctetString.swift	
+++ b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1OctetString.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension ASN1 {
     /// An octet string is a representation of a string of octets.
diff --git a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Strings.swift b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Strings.swift
index f2fc25bd9..27f36f1a9 100644
--- a/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Strings.swift	
+++ b/Sources/Crypto/ASN1/Basic ASN1 Types/ASN1Strings.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension ASN1 {
     /// A UTF8String is roughly what it sounds like. We note that all the string types are encoded as implicitly tagged
diff --git a/Sources/Crypto/ASN1/Basic ASN1 Types/GeneralizedTime.swift b/Sources/Crypto/ASN1/Basic ASN1 Types/GeneralizedTime.swift
index d4c117498..4dc667c58 100644
--- a/Sources/Crypto/ASN1/Basic ASN1 Types/GeneralizedTime.swift	
+++ b/Sources/Crypto/ASN1/Basic ASN1 Types/GeneralizedTime.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension ASN1 {
     struct GeneralizedTime: ASN1ImplicitlyTaggable, Hashable {
diff --git a/Sources/Crypto/ASN1/Basic ASN1 Types/ObjectIdentifier.swift b/Sources/Crypto/ASN1/Basic ASN1 Types/ObjectIdentifier.swift
index e7af81e5a..cec9f15c7 100644
--- a/Sources/Crypto/ASN1/Basic ASN1 Types/ObjectIdentifier.swift	
+++ b/Sources/Crypto/ASN1/Basic ASN1 Types/ObjectIdentifier.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension ASN1 {
     /// An Object Identifier is a representation of some kind of object: really any kind of object.
diff --git a/Sources/Crypto/ASN1/ECDSASignature.swift b/Sources/Crypto/ASN1/ECDSASignature.swift
index 5b901e515..6cf7bd200 100644
--- a/Sources/Crypto/ASN1/ECDSASignature.swift
+++ b/Sources/Crypto/ASN1/ECDSASignature.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension ASN1 {
     /// An ECDSA signature is laid out as follows:
diff --git a/Sources/Crypto/ASN1/PEMDocument.swift b/Sources/Crypto/ASN1/PEMDocument.swift
index 9e0c2b6a0..094c024b5 100644
--- a/Sources/Crypto/ASN1/PEMDocument.swift
+++ b/Sources/Crypto/ASN1/PEMDocument.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension ASN1 {
     /// A PEM document is some data, and a discriminator type that is used to advertise the content.
diff --git a/Sources/Crypto/ASN1/PKCS8PrivateKey.swift b/Sources/Crypto/ASN1/PKCS8PrivateKey.swift
index b247776e5..95890c2a1 100644
--- a/Sources/Crypto/ASN1/PKCS8PrivateKey.swift
+++ b/Sources/Crypto/ASN1/PKCS8PrivateKey.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension ASN1 {
     // A PKCS#8 private key is one of two formats, depending on the version:
diff --git a/Sources/Crypto/ASN1/SEC1PrivateKey.swift b/Sources/Crypto/ASN1/SEC1PrivateKey.swift
index 5236a05c3..30198c39c 100644
--- a/Sources/Crypto/ASN1/SEC1PrivateKey.swift
+++ b/Sources/Crypto/ASN1/SEC1PrivateKey.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension ASN1 {
     // For private keys, SEC 1 uses:
diff --git a/Sources/Crypto/ASN1/SubjectPublicKeyInfo.swift b/Sources/Crypto/ASN1/SubjectPublicKeyInfo.swift
index 826c0478f..bc45f9ce7 100644
--- a/Sources/Crypto/ASN1/SubjectPublicKeyInfo.swift
+++ b/Sources/Crypto/ASN1/SubjectPublicKeyInfo.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension ASN1 {
     struct SubjectPublicKeyInfo: ASN1ImplicitlyTaggable {
diff --git a/Sources/Crypto/Digests/Digest.swift b/Sources/Crypto/Digests/Digest.swift
index 7ebd8c978..79fa724b4 100644
--- a/Sources/Crypto/Digests/Digest.swift
+++ b/Sources/Crypto/Digests/Digest.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// A type that represents the output of a hash.
 public protocol Digest: Hashable, ContiguousBytes, CustomStringConvertible, Sequence where Element == UInt8 {
diff --git a/Sources/Crypto/Digests/HashFunctions.swift b/Sources/Crypto/Digests/HashFunctions.swift
index 24a28d1a1..c06e17838 100644
--- a/Sources/Crypto/Digests/HashFunctions.swift
+++ b/Sources/Crypto/Digests/HashFunctions.swift
@@ -20,7 +20,11 @@ typealias DigestImpl = CoreCryptoDigestImpl
 typealias DigestImpl = OpenSSLDigestImpl
 #endif
 
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// A type that performs cryptographically secure hashing.
 ///
diff --git a/Sources/Crypto/HPKE/Ciphersuite/HPKE-AEAD.swift b/Sources/Crypto/HPKE/Ciphersuite/HPKE-AEAD.swift
index af63f5623..c7675b055 100644
--- a/Sources/Crypto/HPKE/Ciphersuite/HPKE-AEAD.swift
+++ b/Sources/Crypto/HPKE/Ciphersuite/HPKE-AEAD.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 
 extension HPKE {
diff --git a/Sources/Crypto/HPKE/Ciphersuite/HPKE-Ciphersuite.swift b/Sources/Crypto/HPKE/Ciphersuite/HPKE-Ciphersuite.swift
index 81de87a4e..97a726e4f 100644
--- a/Sources/Crypto/HPKE/Ciphersuite/HPKE-Ciphersuite.swift
+++ b/Sources/Crypto/HPKE/Ciphersuite/HPKE-Ciphersuite.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 
 extension HPKE {
diff --git a/Sources/Crypto/HPKE/Ciphersuite/HPKE-KDF.swift b/Sources/Crypto/HPKE/Ciphersuite/HPKE-KDF.swift
index b8bb0f35b..e1654efaf 100644
--- a/Sources/Crypto/HPKE/Ciphersuite/HPKE-KDF.swift
+++ b/Sources/Crypto/HPKE/Ciphersuite/HPKE-KDF.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension HPKE {
     /// The key derivation functions to use in HPKE.
diff --git a/Sources/Crypto/HPKE/Ciphersuite/HPKE-KexKeyDerivation.swift b/Sources/Crypto/HPKE/Ciphersuite/HPKE-KexKeyDerivation.swift
index c3135e54b..ee8aab8f2 100644
--- a/Sources/Crypto/HPKE/Ciphersuite/HPKE-KexKeyDerivation.swift
+++ b/Sources/Crypto/HPKE/Ciphersuite/HPKE-KexKeyDerivation.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 private let suiteIDLabel = Data("KEM".utf8)
 
diff --git a/Sources/Crypto/HPKE/Ciphersuite/HPKE-LabeledExtract.swift b/Sources/Crypto/HPKE/Ciphersuite/HPKE-LabeledExtract.swift
index bd7f4e29c..1d718dd10 100644
--- a/Sources/Crypto/HPKE/Ciphersuite/HPKE-LabeledExtract.swift
+++ b/Sources/Crypto/HPKE/Ciphersuite/HPKE-LabeledExtract.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 private let protocolLabel = Data("HPKE-v1".utf8)
 private let eaePRKLabel = Data("eae_prk".utf8)
diff --git a/Sources/Crypto/HPKE/Ciphersuite/HPKE-Utils.swift b/Sources/Crypto/HPKE/Ciphersuite/HPKE-Utils.swift
index 01cae7183..20d4830fb 100644
--- a/Sources/Crypto/HPKE/Ciphersuite/HPKE-Utils.swift
+++ b/Sources/Crypto/HPKE/Ciphersuite/HPKE-Utils.swift
@@ -14,7 +14,22 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#if canImport(Glibc)
+import Glibc
+#elseif canImport(Musl)
+import Musl
+#elseif os(Windows)
+import CRT
+#elseif canImport(Android)
+import Android
+#else
+import Darwin.C
+#endif
+#else
 import Foundation
+#endif
 
 internal func I2OSP(value: Int, outputByteCount: Int) -> Data {
     precondition(outputByteCount > 0, "Cannot I2OSP with no output length.")
diff --git a/Sources/Crypto/HPKE/Ciphersuite/KEM/Conformances/DHKEM.swift b/Sources/Crypto/HPKE/Ciphersuite/KEM/Conformances/DHKEM.swift
index 52fe85cef..3737c57cb 100644
--- a/Sources/Crypto/HPKE/Ciphersuite/KEM/Conformances/DHKEM.swift
+++ b/Sources/Crypto/HPKE/Ciphersuite/KEM/Conformances/DHKEM.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// A type that ``HPKE`` uses to encode the public key.
 public protocol HPKEPublicKeySerialization {
diff --git a/Sources/Crypto/HPKE/Ciphersuite/KEM/Conformances/HPKE-KEM-Curve25519.swift b/Sources/Crypto/HPKE/Ciphersuite/KEM/Conformances/HPKE-KEM-Curve25519.swift
index 2c03eb94b..ffcd6f075 100644
--- a/Sources/Crypto/HPKE/Ciphersuite/KEM/Conformances/HPKE-KEM-Curve25519.swift
+++ b/Sources/Crypto/HPKE/Ciphersuite/KEM/Conformances/HPKE-KEM-Curve25519.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension Curve25519.KeyAgreement.PrivateKey: HPKEDiffieHellmanPrivateKeyGeneration {}
 
diff --git a/Sources/Crypto/HPKE/Ciphersuite/KEM/Conformances/HPKE-NIST-EC-KEMs.swift b/Sources/Crypto/HPKE/Ciphersuite/KEM/Conformances/HPKE-NIST-EC-KEMs.swift
index 9a8d8f090..ac18b056b 100644
--- a/Sources/Crypto/HPKE/Ciphersuite/KEM/Conformances/HPKE-NIST-EC-KEMs.swift
+++ b/Sources/Crypto/HPKE/Ciphersuite/KEM/Conformances/HPKE-NIST-EC-KEMs.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 
 
diff --git a/Sources/Crypto/HPKE/Ciphersuite/KEM/HPKE-KEM.swift b/Sources/Crypto/HPKE/Ciphersuite/KEM/HPKE-KEM.swift
index 4faee587c..218a66f6e 100644
--- a/Sources/Crypto/HPKE/Ciphersuite/KEM/HPKE-KEM.swift
+++ b/Sources/Crypto/HPKE/Ciphersuite/KEM/HPKE-KEM.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension HPKE {
 	/// The key encapsulation mechanisms to use in HPKE.
diff --git a/Sources/Crypto/HPKE/HPKE-Errors.swift b/Sources/Crypto/HPKE/HPKE-Errors.swift
index cc83de29f..a09f00922 100644
--- a/Sources/Crypto/HPKE/HPKE-Errors.swift
+++ b/Sources/Crypto/HPKE/HPKE-Errors.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension HPKE {
     /// Hybrid public key encryption (HPKE) errors that CryptoKit uses.
diff --git a/Sources/Crypto/HPKE/HPKE.swift b/Sources/Crypto/HPKE/HPKE.swift
index 49e80872b..3306a3726 100644
--- a/Sources/Crypto/HPKE/HPKE.swift
+++ b/Sources/Crypto/HPKE/HPKE.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// A container for hybrid public key encryption (HPKE) operations.
 ///
diff --git a/Sources/Crypto/HPKE/Key Schedule/HPKE-Context.swift b/Sources/Crypto/HPKE/Key Schedule/HPKE-Context.swift
index a018c063c..26fceea67 100644
--- a/Sources/Crypto/HPKE/Key Schedule/HPKE-Context.swift	
+++ b/Sources/Crypto/HPKE/Key Schedule/HPKE-Context.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension HPKE {
     struct Context {
diff --git a/Sources/Crypto/HPKE/Key Schedule/HPKE-KeySchedule.swift b/Sources/Crypto/HPKE/Key Schedule/HPKE-KeySchedule.swift
index dda34b0a7..b27eb4d00 100644
--- a/Sources/Crypto/HPKE/Key Schedule/HPKE-KeySchedule.swift	
+++ b/Sources/Crypto/HPKE/Key Schedule/HPKE-KeySchedule.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension HPKE {
     internal struct KeySchedule {
diff --git a/Sources/Crypto/KEM/KEM.swift b/Sources/Crypto/KEM/KEM.swift
index c66243ebf..ed5326c89 100644
--- a/Sources/Crypto/KEM/KEM.swift
+++ b/Sources/Crypto/KEM/KEM.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// A Key Encapsulation Mechanism
 public enum KEM {
diff --git a/Sources/Crypto/Key Agreement/DH.swift b/Sources/Crypto/Key Agreement/DH.swift
index a39bbd479..0b6182f8c 100644
--- a/Sources/Crypto/Key Agreement/DH.swift	
+++ b/Sources/Crypto/Key Agreement/DH.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// A Diffie-Hellman Key Agreement Key
 public protocol DiffieHellmanKeyAgreement {
diff --git a/Sources/Crypto/Key Agreement/ECDH.swift b/Sources/Crypto/Key Agreement/ECDH.swift
index 03c47769d..2a1fc0509 100644
--- a/Sources/Crypto/Key Agreement/ECDH.swift	
+++ b/Sources/Crypto/Key Agreement/ECDH.swift	
@@ -22,7 +22,11 @@ typealias NISTCurvePublicKeyImpl = OpenSSLNISTCurvePublicKeyImpl
 typealias NISTCurvePrivateKeyImpl = OpenSSLNISTCurvePrivateKeyImpl
 #endif
 
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 // MARK: - Generated file, do NOT edit
 // any edits of this file WILL be overwritten and thus discarded
diff --git a/Sources/Crypto/Key Agreement/ECDH.swift.gyb b/Sources/Crypto/Key Agreement/ECDH.swift.gyb
index d4aae6b7a..a1d944a5a 100644
--- a/Sources/Crypto/Key Agreement/ECDH.swift.gyb	
+++ b/Sources/Crypto/Key Agreement/ECDH.swift.gyb	
@@ -22,7 +22,11 @@ typealias NISTCurvePublicKeyImpl = OpenSSLNISTCurvePublicKeyImpl
 typealias NISTCurvePrivateKeyImpl = OpenSSLNISTCurvePrivateKeyImpl
 #endif
 
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 // MARK: - Generated file, do NOT edit
 // any edits of this file WILL be overwritten and thus discarded
diff --git a/Sources/Crypto/Key Derivation/HKDF.swift b/Sources/Crypto/Key Derivation/HKDF.swift
index 25a0c2f29..8954cfda8 100644
--- a/Sources/Crypto/Key Derivation/HKDF.swift	
+++ b/Sources/Crypto/Key Derivation/HKDF.swift	
@@ -14,7 +14,22 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#if canImport(Glibc)
+import Glibc
+#elseif canImport(Musl)
+import Musl
+#elseif os(Windows)
+import CRT
+#elseif canImport(Android)
+import Android
+#else
+import Darwin.C
+#endif
+#else
 import Foundation
+#endif
 #if canImport(Android)
 import Android
 #endif
diff --git a/Sources/Crypto/Key Wrapping/AESWrap.swift b/Sources/Crypto/Key Wrapping/AESWrap.swift
index fbc0ba768..1888be9ec 100644
--- a/Sources/Crypto/Key Wrapping/AESWrap.swift	
+++ b/Sources/Crypto/Key Wrapping/AESWrap.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 #if !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 typealias AESWRAPImpl = CoreCryptoAESWRAPImpl
diff --git a/Sources/Crypto/Key Wrapping/BoringSSL/AESWrap_boring.swift b/Sources/Crypto/Key Wrapping/BoringSSL/AESWrap_boring.swift
index 2f6320191..2c8ce0d78 100644
--- a/Sources/Crypto/Key Wrapping/BoringSSL/AESWrap_boring.swift	
+++ b/Sources/Crypto/Key Wrapping/BoringSSL/AESWrap_boring.swift	
@@ -15,7 +15,11 @@
 @_exported import CryptoKit
 #else
 @_implementationOnly import CCryptoBoringSSL
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 enum BoringSSLAESWRAPImpl {
     static func wrap(key: SymmetricKey, keyToWrap: SymmetricKey) throws -> Data {
diff --git a/Sources/Crypto/Keys/EC/BoringSSL/Ed25519_boring.swift b/Sources/Crypto/Keys/EC/BoringSSL/Ed25519_boring.swift
index db9bef53d..fb871d6df 100644
--- a/Sources/Crypto/Keys/EC/BoringSSL/Ed25519_boring.swift
+++ b/Sources/Crypto/Keys/EC/BoringSSL/Ed25519_boring.swift
@@ -16,7 +16,11 @@
 #else
 @_implementationOnly import CCryptoBoringSSL
 @_implementationOnly import CCryptoBoringSSLShims
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 // For signing and verifying, we use BoringSSL's Ed25519, not the X25519 stuff.
 extension Curve25519.Signing {
diff --git a/Sources/Crypto/Keys/EC/BoringSSL/NISTCurvesKeys_boring.swift b/Sources/Crypto/Keys/EC/BoringSSL/NISTCurvesKeys_boring.swift
index eb09526ae..fb30c99ef 100644
--- a/Sources/Crypto/Keys/EC/BoringSSL/NISTCurvesKeys_boring.swift
+++ b/Sources/Crypto/Keys/EC/BoringSSL/NISTCurvesKeys_boring.swift
@@ -17,7 +17,11 @@
 @_implementationOnly import CCryptoBoringSSL
 @_implementationOnly import CCryptoBoringSSLShims
 import CryptoBoringWrapper
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 @usableFromInline
 protocol OpenSSLSupportedNISTCurve {
diff --git a/Sources/Crypto/Keys/EC/BoringSSL/X25519Keys_boring.swift b/Sources/Crypto/Keys/EC/BoringSSL/X25519Keys_boring.swift
index 492ff2cee..88ea0a9d9 100644
--- a/Sources/Crypto/Keys/EC/BoringSSL/X25519Keys_boring.swift
+++ b/Sources/Crypto/Keys/EC/BoringSSL/X25519Keys_boring.swift
@@ -16,7 +16,11 @@
 #else
 @_implementationOnly import CCryptoBoringSSL
 @_implementationOnly import CCryptoBoringSSLShims
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension Curve25519.KeyAgreement {
     @usableFromInline
diff --git a/Sources/Crypto/Keys/EC/Ed25519Keys.swift b/Sources/Crypto/Keys/EC/Ed25519Keys.swift
index bc3aecdb2..fb002a289 100644
--- a/Sources/Crypto/Keys/EC/Ed25519Keys.swift
+++ b/Sources/Crypto/Keys/EC/Ed25519Keys.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension Curve25519.Signing {
     static var keyByteCount: Int {
diff --git a/Sources/Crypto/Keys/EC/NISTCurvesKeys.swift b/Sources/Crypto/Keys/EC/NISTCurvesKeys.swift
index fb16fa07b..4aad7cf47 100644
--- a/Sources/Crypto/Keys/EC/NISTCurvesKeys.swift
+++ b/Sources/Crypto/Keys/EC/NISTCurvesKeys.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
diff --git a/Sources/Crypto/Keys/EC/X25519Keys.swift b/Sources/Crypto/Keys/EC/X25519Keys.swift
index 2ea9dce1d..4979ff9f9 100644
--- a/Sources/Crypto/Keys/EC/X25519Keys.swift
+++ b/Sources/Crypto/Keys/EC/X25519Keys.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension Curve25519.KeyAgreement {
     static var keyByteCount: Int {
diff --git a/Sources/Crypto/Keys/Symmetric/SymmetricKeys.swift b/Sources/Crypto/Keys/Symmetric/SymmetricKeys.swift
index 8bb9022ad..c42b0aabb 100644
--- a/Sources/Crypto/Keys/Symmetric/SymmetricKeys.swift
+++ b/Sources/Crypto/Keys/Symmetric/SymmetricKeys.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// The sizes that a symmetric cryptographic key can take.
 ///
diff --git a/Sources/Crypto/Message Authentication Codes/HMAC/HMAC.swift b/Sources/Crypto/Message Authentication Codes/HMAC/HMAC.swift
index 5ef71a555..deb02cdca 100644
--- a/Sources/Crypto/Message Authentication Codes/HMAC/HMAC.swift	
+++ b/Sources/Crypto/Message Authentication Codes/HMAC/HMAC.swift	
@@ -14,7 +14,22 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#if canImport(Glibc)
+import Glibc
+#elseif canImport(Musl)
+import Musl
+#elseif os(Windows)
+import CRT
+#elseif canImport(Android)
+import Android
+#else
+import Darwin.C
+#endif
+#else
 import Foundation
+#endif
 
 /// A hash-based message authentication algorithm.
 ///
diff --git a/Sources/Crypto/Message Authentication Codes/MACFunctions.swift b/Sources/Crypto/Message Authentication Codes/MACFunctions.swift
index a9222a0ca..4c94193c2 100644
--- a/Sources/Crypto/Message Authentication Codes/MACFunctions.swift	
+++ b/Sources/Crypto/Message Authentication Codes/MACFunctions.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 protocol MACAlgorithm {
     associatedtype Key
diff --git a/Sources/Crypto/Message Authentication Codes/MessageAuthenticationCode.swift b/Sources/Crypto/Message Authentication Codes/MessageAuthenticationCode.swift
index 0820072c5..2b8d87a13 100644
--- a/Sources/Crypto/Message Authentication Codes/MessageAuthenticationCode.swift	
+++ b/Sources/Crypto/Message Authentication Codes/MessageAuthenticationCode.swift	
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// A type that represents a message authentication code.
 public protocol MessageAuthenticationCode: Hashable, ContiguousBytes, CustomStringConvertible, Sequence where Element == UInt8 {
diff --git a/Sources/Crypto/Signatures/BoringSSL/ECDSASignature_boring.swift b/Sources/Crypto/Signatures/BoringSSL/ECDSASignature_boring.swift
index 73ab53195..e480df05e 100644
--- a/Sources/Crypto/Signatures/BoringSSL/ECDSASignature_boring.swift
+++ b/Sources/Crypto/Signatures/BoringSSL/ECDSASignature_boring.swift
@@ -17,7 +17,11 @@
 @_implementationOnly import CCryptoBoringSSL
 @_implementationOnly import CCryptoBoringSSLShims
 import CryptoBoringWrapper
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// A wrapper around BoringSSL's ECDSA_SIG with some lifetime management.
 class ECDSASignature {
diff --git a/Sources/Crypto/Signatures/BoringSSL/ECDSA_boring.swift b/Sources/Crypto/Signatures/BoringSSL/ECDSA_boring.swift
index ff367031b..18fa0d1ea 100644
--- a/Sources/Crypto/Signatures/BoringSSL/ECDSA_boring.swift
+++ b/Sources/Crypto/Signatures/BoringSSL/ECDSA_boring.swift
@@ -16,7 +16,11 @@
 #else
 @_implementationOnly import CCryptoBoringSSL
 import CryptoBoringWrapper
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension Data {
     init<D: DataProtocol, Curve: OpenSSLSupportedNISTCurve>(
diff --git a/Sources/Crypto/Signatures/BoringSSL/EdDSA_boring.swift b/Sources/Crypto/Signatures/BoringSSL/EdDSA_boring.swift
index f6219b47b..afd5b51ea 100644
--- a/Sources/Crypto/Signatures/BoringSSL/EdDSA_boring.swift
+++ b/Sources/Crypto/Signatures/BoringSSL/EdDSA_boring.swift
@@ -16,7 +16,11 @@
 #else
 @_implementationOnly import CCryptoBoringSSL
 @_implementationOnly import CCryptoBoringSSLShims
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension Curve25519.Signing.PublicKey {
     // We do this to enable inlinability on these methods.
diff --git a/Sources/Crypto/Signatures/ECDSA.swift b/Sources/Crypto/Signatures/ECDSA.swift
index 4056f1933..049b713b6 100644
--- a/Sources/Crypto/Signatures/ECDSA.swift
+++ b/Sources/Crypto/Signatures/ECDSA.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 // MARK: - Generated file, do NOT edit
 // any edits of this file WILL be overwritten and thus discarded
 // see section `gyb` in `README` for details.
diff --git a/Sources/Crypto/Signatures/ECDSA.swift.gyb b/Sources/Crypto/Signatures/ECDSA.swift.gyb
index f297738f4..05ed8e3c4 100644
--- a/Sources/Crypto/Signatures/ECDSA.swift.gyb
+++ b/Sources/Crypto/Signatures/ECDSA.swift.gyb
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 // MARK: - Generated file, do NOT edit
 // any edits of this file WILL be overwritten and thus discarded
 // see section `gyb` in `README` for details.
diff --git a/Sources/Crypto/Signatures/Ed25519.swift b/Sources/Crypto/Signatures/Ed25519.swift
index bcec7a600..670b243ca 100644
--- a/Sources/Crypto/Signatures/Ed25519.swift
+++ b/Sources/Crypto/Signatures/Ed25519.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 protocol DigestValidator {
     associatedtype Signature
diff --git a/Sources/Crypto/Signatures/Signature.swift b/Sources/Crypto/Signatures/Signature.swift
index 33a5c7f70..2f36ce5bd 100644
--- a/Sources/Crypto/Signatures/Signature.swift
+++ b/Sources/Crypto/Signatures/Signature.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 protocol SignatureVerification {
     func verifySignature(signature: Data, data: Data) throws -> Bool
diff --git a/Sources/Crypto/Util/BoringSSL/SafeCompare_boring.swift b/Sources/Crypto/Util/BoringSSL/SafeCompare_boring.swift
index af93dc8d1..e769535bc 100644
--- a/Sources/Crypto/Util/BoringSSL/SafeCompare_boring.swift
+++ b/Sources/Crypto/Util/BoringSSL/SafeCompare_boring.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// This function performs a safe comparison between two buffers of bytes. It exists as a temporary shim until we refactor
 /// some of the usage sites to pass better data structures to us.
diff --git a/Sources/Crypto/Util/PrettyBytes.swift b/Sources/Crypto/Util/PrettyBytes.swift
index 7610e5c0d..5b34bf383 100644
--- a/Sources/Crypto/Util/PrettyBytes.swift
+++ b/Sources/Crypto/Util/PrettyBytes.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 enum ByteHexEncodingErrors: Error {
     case incorrectHexValue
diff --git a/Sources/Crypto/Util/SafeCompare.swift b/Sources/Crypto/Util/SafeCompare.swift
index 916c19085..cbe520239 100644
--- a/Sources/Crypto/Util/SafeCompare.swift
+++ b/Sources/Crypto/Util/SafeCompare.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 internal func safeCompare<LHS: ContiguousBytes, RHS: ContiguousBytes>(_ lhs: LHS, _ rhs: RHS) -> Bool {
     #if !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
diff --git a/Sources/Crypto/Util/SecureBytes.swift b/Sources/Crypto/Util/SecureBytes.swift
index 7bfcb98ab..aee6205a3 100644
--- a/Sources/Crypto/Util/SecureBytes.swift
+++ b/Sources/Crypto/Util/SecureBytes.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 private let emptyStorage:SecureBytes.Backing = SecureBytes.Backing.createEmpty()
 
diff --git a/Sources/Crypto/Util/Zeroization.swift b/Sources/Crypto/Util/Zeroization.swift
index 54f760141..8622723b6 100644
--- a/Sources/Crypto/Util/Zeroization.swift
+++ b/Sources/Crypto/Util/Zeroization.swift
@@ -14,7 +14,11 @@
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 @_exported import CryptoKit
 #else
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 protocol Zeroization {
     mutating func zeroize()
diff --git a/Sources/CryptoBoringWrapper/AEAD/BoringSSLAEAD.swift b/Sources/CryptoBoringWrapper/AEAD/BoringSSLAEAD.swift
index 7ef217157..64af28b32 100644
--- a/Sources/CryptoBoringWrapper/AEAD/BoringSSLAEAD.swift
+++ b/Sources/CryptoBoringWrapper/AEAD/BoringSSLAEAD.swift
@@ -14,7 +14,12 @@
 
 @_implementationOnly import CCryptoBoringSSL
 @_implementationOnly import CCryptoBoringSSLShims
+
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// An abstraction over a BoringSSL AEAD
 public enum BoringSSLAEAD {
diff --git a/Sources/CryptoBoringWrapper/Util/ArbitraryPrecisionInteger.swift b/Sources/CryptoBoringWrapper/Util/ArbitraryPrecisionInteger.swift
index ebf60ba17..edf74e40a 100644
--- a/Sources/CryptoBoringWrapper/Util/ArbitraryPrecisionInteger.swift
+++ b/Sources/CryptoBoringWrapper/Util/ArbitraryPrecisionInteger.swift
@@ -16,7 +16,11 @@
 #else
 @_implementationOnly import CCryptoBoringSSL
 @_implementationOnly import CCryptoBoringSSLShims
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// A wrapper around the OpenSSL BIGNUM object that is appropriately lifetime managed,
 /// and that provides better Swift types for this object.
diff --git a/Sources/CryptoBoringWrapper/Util/FiniteFieldArithmeticContext.swift b/Sources/CryptoBoringWrapper/Util/FiniteFieldArithmeticContext.swift
index 32ae2083e..8790189d7 100644
--- a/Sources/CryptoBoringWrapper/Util/FiniteFieldArithmeticContext.swift
+++ b/Sources/CryptoBoringWrapper/Util/FiniteFieldArithmeticContext.swift
@@ -15,7 +15,11 @@
 @_exported import CryptoKit
 #else
 @_implementationOnly import CCryptoBoringSSL
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// A context for performing mathematical operations on ArbitraryPrecisionIntegers over a finite field.
 ///
diff --git a/Sources/_CryptoExtras/AES/AES_CBC.swift b/Sources/_CryptoExtras/AES/AES_CBC.swift
index 3363ddbd5..7c2ba8b22 100644
--- a/Sources/_CryptoExtras/AES/AES_CBC.swift
+++ b/Sources/_CryptoExtras/AES/AES_CBC.swift
@@ -13,7 +13,11 @@
 //===----------------------------------------------------------------------===//
 
 import Crypto
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension AES {
     /// The Advanced Encryption Standard (AES) Cipher Block Chaining (CBC) cipher
diff --git a/Sources/_CryptoExtras/AES/AES_CFB.swift b/Sources/_CryptoExtras/AES/AES_CFB.swift
index c11ade316..9d37d8c93 100644
--- a/Sources/_CryptoExtras/AES/AES_CFB.swift
+++ b/Sources/_CryptoExtras/AES/AES_CFB.swift
@@ -13,7 +13,11 @@
 //===----------------------------------------------------------------------===//
 
 import Crypto
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 @usableFromInline
 typealias AESCFBImpl = OpenSSLAESCFBImpl
diff --git a/Sources/_CryptoExtras/AES/AES_CTR.swift b/Sources/_CryptoExtras/AES/AES_CTR.swift
index 0972e6c6c..17b71aee3 100644
--- a/Sources/_CryptoExtras/AES/AES_CTR.swift
+++ b/Sources/_CryptoExtras/AES/AES_CTR.swift
@@ -13,7 +13,11 @@
 //===----------------------------------------------------------------------===//
 
 import Crypto
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 @usableFromInline
 typealias AESCTRImpl = OpenSSLAESCTRImpl
diff --git a/Sources/_CryptoExtras/AES/AES_GCM_SIV.swift b/Sources/_CryptoExtras/AES/AES_GCM_SIV.swift
index 8bce512cc..1ed739457 100644
--- a/Sources/_CryptoExtras/AES/AES_GCM_SIV.swift
+++ b/Sources/_CryptoExtras/AES/AES_GCM_SIV.swift
@@ -16,7 +16,11 @@ import Crypto
 @_implementationOnly import CCryptoBoringSSL
 @_implementationOnly import CCryptoBoringSSLShims
 import CryptoBoringWrapper
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// Types associated with the AES GCM SIV algorithm
 extension AES.GCM {
diff --git a/Sources/_CryptoExtras/AES/Block Function.swift b/Sources/_CryptoExtras/AES/Block Function.swift
index 3db5f73d3..a7948bd3f 100644
--- a/Sources/_CryptoExtras/AES/Block Function.swift	
+++ b/Sources/_CryptoExtras/AES/Block Function.swift	
@@ -16,7 +16,11 @@ import Crypto
 @_implementationOnly import CCryptoBoringSSL
 @_implementationOnly import CCryptoBoringSSLShims
 import CryptoBoringWrapper
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension AES {
     private static let blockSize = 128 / 8
diff --git a/Sources/_CryptoExtras/AES/BoringSSL/AES_CFB_boring.swift b/Sources/_CryptoExtras/AES/BoringSSL/AES_CFB_boring.swift
index 578302840..1448dab76 100644
--- a/Sources/_CryptoExtras/AES/BoringSSL/AES_CFB_boring.swift
+++ b/Sources/_CryptoExtras/AES/BoringSSL/AES_CFB_boring.swift
@@ -14,7 +14,12 @@
 
 @_implementationOnly import CCryptoBoringSSL
 import Crypto
+
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 @usableFromInline
 enum OpenSSLAESCFBImpl {
diff --git a/Sources/_CryptoExtras/AES/BoringSSL/AES_CTR_boring.swift b/Sources/_CryptoExtras/AES/BoringSSL/AES_CTR_boring.swift
index 8ec43c7cc..c3c5f400f 100644
--- a/Sources/_CryptoExtras/AES/BoringSSL/AES_CTR_boring.swift
+++ b/Sources/_CryptoExtras/AES/BoringSSL/AES_CTR_boring.swift
@@ -14,7 +14,12 @@
 
 @_implementationOnly import CCryptoBoringSSL
 import Crypto
+
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 @usableFromInline
 enum OpenSSLAESCTRImpl {
diff --git a/Sources/_CryptoExtras/AES/BoringSSL/AES_GCM_SIV_boring.swift b/Sources/_CryptoExtras/AES/BoringSSL/AES_GCM_SIV_boring.swift
index 8312db7a5..c657e3457 100644
--- a/Sources/_CryptoExtras/AES/BoringSSL/AES_GCM_SIV_boring.swift
+++ b/Sources/_CryptoExtras/AES/BoringSSL/AES_GCM_SIV_boring.swift
@@ -18,7 +18,12 @@
 @_implementationOnly import CCryptoBoringSSLShims
 import Crypto
 import CryptoBoringWrapper
+
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 extension BoringSSLAEAD {
     /// Seal a given message.
diff --git a/Sources/_CryptoExtras/ChaCha20CTR/BoringSSL/ChaCha20CTR_boring.swift b/Sources/_CryptoExtras/ChaCha20CTR/BoringSSL/ChaCha20CTR_boring.swift
index e4684c392..6bca1ff14 100644
--- a/Sources/_CryptoExtras/ChaCha20CTR/BoringSSL/ChaCha20CTR_boring.swift
+++ b/Sources/_CryptoExtras/ChaCha20CTR/BoringSSL/ChaCha20CTR_boring.swift
@@ -16,7 +16,12 @@
 @_implementationOnly import CCryptoBoringSSLShims
 import Crypto
 import CryptoBoringWrapper
+
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 enum OpenSSLChaCha20CTRImpl {
     static func encrypt<M: DataProtocol, N: ContiguousBytes>(
diff --git a/Sources/_CryptoExtras/ChaCha20CTR/ChaCha20CTR.swift b/Sources/_CryptoExtras/ChaCha20CTR/ChaCha20CTR.swift
index 449bd7a05..2bf2947d7 100644
--- a/Sources/_CryptoExtras/ChaCha20CTR/ChaCha20CTR.swift
+++ b/Sources/_CryptoExtras/ChaCha20CTR/ChaCha20CTR.swift
@@ -16,7 +16,11 @@
 @_implementationOnly import CCryptoBoringSSLShims
 import Crypto
 import CryptoBoringWrapper
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 typealias ChaCha20CTRImpl = OpenSSLChaCha20CTRImpl
 
diff --git a/Sources/_CryptoExtras/ECToolbox/BoringSSL/ECToolbox_boring.swift b/Sources/_CryptoExtras/ECToolbox/BoringSSL/ECToolbox_boring.swift
index de2868915..d9b66a99e 100644
--- a/Sources/_CryptoExtras/ECToolbox/BoringSSL/ECToolbox_boring.swift
+++ b/Sources/_CryptoExtras/ECToolbox/BoringSSL/ECToolbox_boring.swift
@@ -13,7 +13,12 @@
 //===----------------------------------------------------------------------===//
 import Crypto
 import CryptoBoringWrapper
+
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// NOTE: This protocol is different from `Crypto.OpenSSLSupportedNISTCurve` module and has additional requirements to
 /// support ECToolbox. It is (re-)defined here because its counterpart in the Crypto module is only conditionally
diff --git a/Sources/_CryptoExtras/ECToolbox/ECToolbox.swift b/Sources/_CryptoExtras/ECToolbox/ECToolbox.swift
index 8d4366a64..7bcc3f863 100644
--- a/Sources/_CryptoExtras/ECToolbox/ECToolbox.swift
+++ b/Sources/_CryptoExtras/ECToolbox/ECToolbox.swift
@@ -12,7 +12,11 @@
 //
 //===----------------------------------------------------------------------===//
 import Crypto
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 #if canImport(Darwin) && !CRYPTO_IN_SWIFTPM
 typealias SupportedCurveDetailsImpl = CorecryptoSupportedNISTCurve
diff --git a/Sources/_CryptoExtras/H2G/HashToField.swift b/Sources/_CryptoExtras/H2G/HashToField.swift
index 9c8b0fd01..59db76291 100644
--- a/Sources/_CryptoExtras/H2G/HashToField.swift
+++ b/Sources/_CryptoExtras/H2G/HashToField.swift
@@ -11,7 +11,22 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#if canImport(Glibc)
+import Glibc
+#elseif canImport(Musl)
+import Musl
+#elseif os(Windows)
+import CRT
+#elseif canImport(Android)
+import Android
+#else
+import Darwin.C
+#endif
+#else
 import Foundation
+#endif
 import Crypto
 
 extension Data {
diff --git a/Sources/_CryptoExtras/Key Derivation/KDF.swift b/Sources/_CryptoExtras/Key Derivation/KDF.swift
index f07413e77..f27c3a617 100644
--- a/Sources/_CryptoExtras/Key Derivation/KDF.swift	
+++ b/Sources/_CryptoExtras/Key Derivation/KDF.swift	
@@ -12,11 +12,15 @@
 //
 //===----------------------------------------------------------------------===//
 import Crypto
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 #if canImport(Darwin) || swift(>=5.9.1)
 import Foundation
 #else
 @preconcurrency import Foundation
 #endif
+#endif
 
 /// A container for Key Detivation Function algorithms.
 public enum KDF: Sendable {
diff --git a/Sources/_CryptoExtras/Key Derivation/PBKDF2/BoringSSL/PBKDF2_boring.swift b/Sources/_CryptoExtras/Key Derivation/PBKDF2/BoringSSL/PBKDF2_boring.swift
index e19ceefdd..f7940dcb3 100644
--- a/Sources/_CryptoExtras/Key Derivation/PBKDF2/BoringSSL/PBKDF2_boring.swift	
+++ b/Sources/_CryptoExtras/Key Derivation/PBKDF2/BoringSSL/PBKDF2_boring.swift	
@@ -14,7 +14,11 @@
 import Crypto
 
 #if canImport(Darwin) || swift(>=5.9.1)
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 #else
 @preconcurrency import Foundation
 #endif
diff --git a/Sources/_CryptoExtras/Key Derivation/PBKDF2/BoringSSL/PBKDF2_commoncrypto.swift b/Sources/_CryptoExtras/Key Derivation/PBKDF2/BoringSSL/PBKDF2_commoncrypto.swift
index 61bad9f95..a44380f8e 100644
--- a/Sources/_CryptoExtras/Key Derivation/PBKDF2/BoringSSL/PBKDF2_commoncrypto.swift	
+++ b/Sources/_CryptoExtras/Key Derivation/PBKDF2/BoringSSL/PBKDF2_commoncrypto.swift	
@@ -13,11 +13,15 @@
 //===----------------------------------------------------------------------===//
 import Crypto
 
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 #if canImport(Darwin) || swift(>=5.9.1)
 import Foundation
 #else
 @preconcurrency import Foundation
 #endif
+#endif
 
 #if canImport(CommonCrypto)
 @_implementationOnly import CommonCrypto
diff --git a/Sources/_CryptoExtras/Key Derivation/PBKDF2/PBKDF2.swift b/Sources/_CryptoExtras/Key Derivation/PBKDF2/PBKDF2.swift
index 3a8556537..e3dd9aaec 100644
--- a/Sources/_CryptoExtras/Key Derivation/PBKDF2/PBKDF2.swift	
+++ b/Sources/_CryptoExtras/Key Derivation/PBKDF2/PBKDF2.swift	
@@ -12,11 +12,15 @@
 //
 //===----------------------------------------------------------------------===//
 import Crypto
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 #if canImport(Darwin) || swift(>=5.9.1)
 import Foundation
 #else
 @preconcurrency import Foundation
 #endif
+#endif
 
 #if canImport(CommonCrypto)
 fileprivate typealias BackingPBKDF2 = CommonCryptoPBKDF2
diff --git a/Sources/_CryptoExtras/Key Derivation/Scrypt/BoringSSL/Scrypt_boring.swift b/Sources/_CryptoExtras/Key Derivation/Scrypt/BoringSSL/Scrypt_boring.swift
index 00520ea19..11ed1316e 100644
--- a/Sources/_CryptoExtras/Key Derivation/Scrypt/BoringSSL/Scrypt_boring.swift	
+++ b/Sources/_CryptoExtras/Key Derivation/Scrypt/BoringSSL/Scrypt_boring.swift	
@@ -16,11 +16,26 @@
 @_implementationOnly import CCryptoBoringSSLShims
 import Crypto
 
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#if canImport(Glibc)
+import Glibc
+#elseif canImport(Musl)
+import Musl
+#elseif os(Windows)
+import CRT
+#elseif canImport(Android)
+import Android
+#else
+import Darwin.C
+#endif
+#else
 #if canImport(Darwin) || swift(>=5.9.1)
 import Foundation
 #else
 @preconcurrency import Foundation
 #endif
+#endif
 
 #if canImport(Android)
 import Android
diff --git a/Sources/_CryptoExtras/Key Derivation/Scrypt/Scrypt.swift b/Sources/_CryptoExtras/Key Derivation/Scrypt/Scrypt.swift
index cae5f773e..8b66e0b00 100644
--- a/Sources/_CryptoExtras/Key Derivation/Scrypt/Scrypt.swift	
+++ b/Sources/_CryptoExtras/Key Derivation/Scrypt/Scrypt.swift	
@@ -12,11 +12,15 @@
 //
 //===----------------------------------------------------------------------===//
 import Crypto
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 #if canImport(Darwin) || swift(>=5.9.1)
 import Foundation
 #else
 @preconcurrency import Foundation
 #endif
+#endif
 
 fileprivate typealias BackingScrypt = BoringSSLScrypt
 
diff --git a/Sources/_CryptoExtras/OPRFs/OPRF.swift b/Sources/_CryptoExtras/OPRFs/OPRF.swift
index e61dcaa10..db030e6b1 100644
--- a/Sources/_CryptoExtras/OPRFs/OPRF.swift
+++ b/Sources/_CryptoExtras/OPRFs/OPRF.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import Crypto
 
 /// (Verifiable Partly-)Oblivious Pseudorandom Functions
diff --git a/Sources/_CryptoExtras/OPRFs/OPRFClient.swift b/Sources/_CryptoExtras/OPRFs/OPRFClient.swift
index bf20458d6..e921a63c0 100644
--- a/Sources/_CryptoExtras/OPRFs/OPRFClient.swift
+++ b/Sources/_CryptoExtras/OPRFs/OPRFClient.swift
@@ -12,7 +12,11 @@
 //
 //===----------------------------------------------------------------------===//
 import Crypto
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 @available(macOS 10.15, iOS 13.2, tvOS 13.2, watchOS 6.1, *)
 extension OPRF {
diff --git a/Sources/_CryptoExtras/OPRFs/OPRFServer.swift b/Sources/_CryptoExtras/OPRFs/OPRFServer.swift
index cf858f7fe..38bdaa4d8 100644
--- a/Sources/_CryptoExtras/OPRFs/OPRFServer.swift
+++ b/Sources/_CryptoExtras/OPRFs/OPRFServer.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import Crypto
 
 @available(macOS 10.15, iOS 13.2, tvOS 13.2, watchOS 6.1, *)
diff --git a/Sources/_CryptoExtras/OPRFs/VOPRF+API.swift b/Sources/_CryptoExtras/OPRFs/VOPRF+API.swift
index f2285c777..11acfab1f 100644
--- a/Sources/_CryptoExtras/OPRFs/VOPRF+API.swift
+++ b/Sources/_CryptoExtras/OPRFs/VOPRF+API.swift
@@ -12,7 +12,11 @@
 //
 //===----------------------------------------------------------------------===//
 import Crypto
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 // MARK: - P384 + VPORF (P384-SHA384)
 extension P384 {
diff --git a/Sources/_CryptoExtras/OPRFs/VOPRFClient.swift b/Sources/_CryptoExtras/OPRFs/VOPRFClient.swift
index 8687e3bba..fc6232ff5 100644
--- a/Sources/_CryptoExtras/OPRFs/VOPRFClient.swift
+++ b/Sources/_CryptoExtras/OPRFs/VOPRFClient.swift
@@ -12,7 +12,11 @@
 //
 //===----------------------------------------------------------------------===//
 import Crypto
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 @available(macOS 10.15, iOS 13.2, tvOS 13.2, watchOS 6.1, *)
 extension OPRF {
diff --git a/Sources/_CryptoExtras/OPRFs/VOPRFServer.swift b/Sources/_CryptoExtras/OPRFs/VOPRFServer.swift
index c5de9040f..f04eeab9b 100644
--- a/Sources/_CryptoExtras/OPRFs/VOPRFServer.swift
+++ b/Sources/_CryptoExtras/OPRFs/VOPRFServer.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import Crypto
 
 @available(macOS 10.15, iOS 13.2, tvOS 13.2, watchOS 6.1, *)
diff --git a/Sources/_CryptoExtras/RSA/RSA+BlindSigning.swift b/Sources/_CryptoExtras/RSA/RSA+BlindSigning.swift
index cf866dce9..7b7ad47ab 100644
--- a/Sources/_CryptoExtras/RSA/RSA+BlindSigning.swift
+++ b/Sources/_CryptoExtras/RSA/RSA+BlindSigning.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import Crypto
 import CryptoBoringWrapper
 
diff --git a/Sources/_CryptoExtras/RSA/RSA.swift b/Sources/_CryptoExtras/RSA/RSA.swift
index a7d5652c0..957e74ecb 100644
--- a/Sources/_CryptoExtras/RSA/RSA.swift
+++ b/Sources/_CryptoExtras/RSA/RSA.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import Crypto
 import CryptoBoringWrapper
 import SwiftASN1
diff --git a/Sources/_CryptoExtras/RSA/RSA_boring.swift b/Sources/_CryptoExtras/RSA/RSA_boring.swift
index 1baf9b400..942487ad3 100644
--- a/Sources/_CryptoExtras/RSA/RSA_boring.swift
+++ b/Sources/_CryptoExtras/RSA/RSA_boring.swift
@@ -17,7 +17,23 @@
 @_implementationOnly import CCryptoBoringSSLShims
 import Crypto
 import CryptoBoringWrapper
+
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#if canImport(Glibc)
+import Glibc
+#elseif canImport(Musl)
+import Musl
+#elseif os(Windows)
+import CRT
+#elseif canImport(Android)
+import Android
+#else
+import Darwin.C
+#endif
+#else
 import Foundation
+#endif
 
 internal struct BoringSSLRSAPublicKey: Sendable {
     private var backing: Backing
diff --git a/Sources/_CryptoExtras/RSA/RSA_security.swift b/Sources/_CryptoExtras/RSA/RSA_security.swift
index 114012de6..d9c4ceb0e 100644
--- a/Sources/_CryptoExtras/RSA/RSA_security.swift
+++ b/Sources/_CryptoExtras/RSA/RSA_security.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import Crypto
 
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
diff --git a/Sources/_CryptoExtras/Util/BoringSSLHelpers.swift b/Sources/_CryptoExtras/Util/BoringSSLHelpers.swift
index 49f929a8a..6b861e2eb 100644
--- a/Sources/_CryptoExtras/Util/BoringSSLHelpers.swift
+++ b/Sources/_CryptoExtras/Util/BoringSSLHelpers.swift
@@ -15,7 +15,11 @@
 // NOTE: This file is unconditionally compiled because RSABSSA is implemented using BoringSSL on all platforms.
 @_implementationOnly import CCryptoBoringSSL
 @_implementationOnly import CCryptoBoringSSLShims
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import Crypto
 
 internal enum BIOHelper {
diff --git a/Sources/_CryptoExtras/Util/I2OSP.swift b/Sources/_CryptoExtras/Util/I2OSP.swift
index d3d201533..8e73e5085 100644
--- a/Sources/_CryptoExtras/Util/I2OSP.swift
+++ b/Sources/_CryptoExtras/Util/I2OSP.swift
@@ -11,7 +11,22 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#if canImport(Glibc)
+import Glibc
+#elseif canImport(Musl)
+import Musl
+#elseif os(Windows)
+import CRT
+#elseif canImport(Android)
+import Android
+#else
+import Darwin.C
+#endif
+#else
 import Foundation
+#endif
 
 func I2OSP(value: Int, outputByteCount: Int) -> Data {
     precondition(outputByteCount > 0, "Cannot I2OSP with no output length.")
diff --git a/Sources/_CryptoExtras/Util/PEMDocument.swift b/Sources/_CryptoExtras/Util/PEMDocument.swift
index 49ac67b98..0ec501560 100644
--- a/Sources/_CryptoExtras/Util/PEMDocument.swift
+++ b/Sources/_CryptoExtras/Util/PEMDocument.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import Crypto
 
 enum ASN1 {
diff --git a/Sources/_CryptoExtras/Util/PrettyBytes.swift b/Sources/_CryptoExtras/Util/PrettyBytes.swift
index 7610e5c0d..5b34bf383 100644
--- a/Sources/_CryptoExtras/Util/PrettyBytes.swift
+++ b/Sources/_CryptoExtras/Util/PrettyBytes.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 enum ByteHexEncodingErrors: Error {
     case incorrectHexValue
diff --git a/Sources/_CryptoExtras/ZKPs/DLEQ.swift b/Sources/_CryptoExtras/ZKPs/DLEQ.swift
index ff748f85f..0e4843f45 100644
--- a/Sources/_CryptoExtras/ZKPs/DLEQ.swift
+++ b/Sources/_CryptoExtras/ZKPs/DLEQ.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import Crypto
 
 /// A DLEQ Proof as described in https://cfrg.github.io/draft-irtf-cfrg-voprf/draft-irtf-cfrg-voprf.html#name-generateproof
diff --git a/Sources/crypto-shasum/main.swift b/Sources/crypto-shasum/main.swift
index b80d29d8c..dae3e6059 100644
--- a/Sources/crypto-shasum/main.swift
+++ b/Sources/crypto-shasum/main.swift
@@ -11,6 +11,7 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+
 import Foundation
 import Crypto
 
diff --git a/Tests/CryptoTests/Authenticated Encryption/AES-GCM-Runner.swift b/Tests/CryptoTests/Authenticated Encryption/AES-GCM-Runner.swift
index 8e3e6c240..074e7e504 100644
--- a/Tests/CryptoTests/Authenticated Encryption/AES-GCM-Runner.swift	
+++ b/Tests/CryptoTests/Authenticated Encryption/AES-GCM-Runner.swift	
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
diff --git a/Tests/CryptoTests/Authenticated Encryption/ChaChaPoly-Runner.swift b/Tests/CryptoTests/Authenticated Encryption/ChaChaPoly-Runner.swift
index 4ecc17388..eca04a890 100644
--- a/Tests/CryptoTests/Authenticated Encryption/ChaChaPoly-Runner.swift	
+++ b/Tests/CryptoTests/Authenticated Encryption/ChaChaPoly-Runner.swift	
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
diff --git a/Tests/CryptoTests/ECDH/BoringSSL/ASN1.swift b/Tests/CryptoTests/ECDH/BoringSSL/ASN1.swift
index 2b2457b84..8a5e1f675 100644
--- a/Tests/CryptoTests/ECDH/BoringSSL/ASN1.swift
+++ b/Tests/CryptoTests/ECDH/BoringSSL/ASN1.swift
@@ -1,3 +1,5 @@
+import XCTest
+
 //===----------------------------------------------------------------------===//
 //
 // This source file is part of the SwiftCrypto open source project
@@ -11,8 +13,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
-import XCTest
+#endif
 
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 // Skip tests that require @testable imports of CryptoKit.
diff --git a/Tests/CryptoTests/ECDH/BoringSSL/secpECDH_Runner_boring.swift b/Tests/CryptoTests/ECDH/BoringSSL/secpECDH_Runner_boring.swift
index ef6cd8da8..dc68ee962 100644
--- a/Tests/CryptoTests/ECDH/BoringSSL/secpECDH_Runner_boring.swift
+++ b/Tests/CryptoTests/ECDH/BoringSSL/secpECDH_Runner_boring.swift
@@ -1,3 +1,5 @@
+import XCTest
+
 //===----------------------------------------------------------------------===//
 //
 // This source file is part of the SwiftCrypto open source project
@@ -11,8 +13,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
-import XCTest
+#endif
 
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
 // Skip tests that require @testable imports of CryptoKit.
diff --git a/Tests/CryptoTests/ECDH/X25519-Runner.swift b/Tests/CryptoTests/ECDH/X25519-Runner.swift
index c03bd7b8b..41deb8702 100644
--- a/Tests/CryptoTests/ECDH/X25519-Runner.swift
+++ b/Tests/CryptoTests/ECDH/X25519-Runner.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
diff --git a/Tests/CryptoTests/ECDH/secpECDH_Runner.swift b/Tests/CryptoTests/ECDH/secpECDH_Runner.swift
index aa89bbbde..e03efa1d5 100644
--- a/Tests/CryptoTests/ECDH/secpECDH_Runner.swift
+++ b/Tests/CryptoTests/ECDH/secpECDH_Runner.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
diff --git a/Tests/CryptoTests/HPKE/HPKETests-TestVectors.swift b/Tests/CryptoTests/HPKE/HPKETests-TestVectors.swift
index 56e941416..52a750a13 100644
--- a/Tests/CryptoTests/HPKE/HPKETests-TestVectors.swift
+++ b/Tests/CryptoTests/HPKE/HPKETests-TestVectors.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
diff --git a/Tests/CryptoTests/HPKE/HPKETests.swift b/Tests/CryptoTests/HPKE/HPKETests.swift
index cca6397ca..fd2b74ea3 100644
--- a/Tests/CryptoTests/HPKE/HPKETests.swift
+++ b/Tests/CryptoTests/HPKE/HPKETests.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
diff --git a/Tests/CryptoTests/Key Derivation/ECprivateKeysFromSeeds.swift b/Tests/CryptoTests/Key Derivation/ECprivateKeysFromSeeds.swift
index 06ebe89e3..ef4d0cef2 100644
--- a/Tests/CryptoTests/Key Derivation/ECprivateKeysFromSeeds.swift	
+++ b/Tests/CryptoTests/Key Derivation/ECprivateKeysFromSeeds.swift	
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
diff --git a/Tests/CryptoTests/Signatures/ECDSA/ECDSASignatureTests.swift b/Tests/CryptoTests/Signatures/ECDSA/ECDSASignatureTests.swift
index c60b33170..23acf1c85 100644
--- a/Tests/CryptoTests/Signatures/ECDSA/ECDSASignatureTests.swift
+++ b/Tests/CryptoTests/Signatures/ECDSA/ECDSASignatureTests.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 
 #if CRYPTO_IN_SWIFTPM && !CRYPTO_IN_SWIFTPM_FORCE_BUILD_API
diff --git a/Tests/CryptoTests/Utils/PrettyBytes.swift b/Tests/CryptoTests/Utils/PrettyBytes.swift
index 7610e5c0d..5b34bf383 100644
--- a/Tests/CryptoTests/Utils/PrettyBytes.swift
+++ b/Tests/CryptoTests/Utils/PrettyBytes.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 enum ByteHexEncodingErrors: Error {
     case incorrectHexValue
diff --git a/Tests/CryptoTests/Utils/RFCVector.swift b/Tests/CryptoTests/Utils/RFCVector.swift
index edf5540c2..ce09b655c 100644
--- a/Tests/CryptoTests/Utils/RFCVector.swift
+++ b/Tests/CryptoTests/Utils/RFCVector.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// This is a not-very-performant decoder of the RFC formatted test vectors.
 ///
diff --git a/Tests/CryptoTests/Utils/SplitData.swift b/Tests/CryptoTests/Utils/SplitData.swift
index e0c17e48f..37283d85e 100644
--- a/Tests/CryptoTests/Utils/SplitData.swift
+++ b/Tests/CryptoTests/Utils/SplitData.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import Dispatch
 
 // A testing utility that creates one contiguous and one discontiguous representation of the given Data.
diff --git a/Tests/_CryptoExtrasTests/AES Block Function Tests.swift b/Tests/_CryptoExtrasTests/AES Block Function Tests.swift
index 776962d45..926cc04fc 100644
--- a/Tests/_CryptoExtrasTests/AES Block Function Tests.swift	
+++ b/Tests/_CryptoExtrasTests/AES Block Function Tests.swift	
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 import Crypto
 import _CryptoExtras
diff --git a/Tests/_CryptoExtrasTests/AES-GCM-SIV-Runner.swift b/Tests/_CryptoExtrasTests/AES-GCM-SIV-Runner.swift
index 227e73c3c..6cfa781f3 100644
--- a/Tests/_CryptoExtrasTests/AES-GCM-SIV-Runner.swift
+++ b/Tests/_CryptoExtrasTests/AES-GCM-SIV-Runner.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 import Crypto
 import _CryptoExtras
diff --git a/Tests/_CryptoExtrasTests/AES_CBCTests.swift b/Tests/_CryptoExtrasTests/AES_CBCTests.swift
index b42131c69..b2ba34eaa 100644
--- a/Tests/_CryptoExtrasTests/AES_CBCTests.swift
+++ b/Tests/_CryptoExtrasTests/AES_CBCTests.swift
@@ -13,7 +13,11 @@
 //===----------------------------------------------------------------------===//
 
 import Crypto
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import _CryptoExtras
 import XCTest
 
diff --git a/Tests/_CryptoExtrasTests/AES_CTRTests.swift b/Tests/_CryptoExtrasTests/AES_CTRTests.swift
index e154b9b4a..2206967f9 100644
--- a/Tests/_CryptoExtrasTests/AES_CTRTests.swift
+++ b/Tests/_CryptoExtrasTests/AES_CTRTests.swift
@@ -13,7 +13,11 @@
 //===----------------------------------------------------------------------===//
 
 import Crypto
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 @testable import _CryptoExtras
 import XCTest
 
diff --git a/Tests/_CryptoExtrasTests/ChaCha20CTRTests.swift b/Tests/_CryptoExtrasTests/ChaCha20CTRTests.swift
index b86bfcaac..fde4a79fc 100644
--- a/Tests/_CryptoExtrasTests/ChaCha20CTRTests.swift
+++ b/Tests/_CryptoExtrasTests/ChaCha20CTRTests.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 import Crypto
 import _CryptoExtras
diff --git a/Tests/_CryptoExtrasTests/TestRSAEncryption.swift b/Tests/_CryptoExtrasTests/TestRSAEncryption.swift
index 63ad1e0f3..b6d45c3b6 100644
--- a/Tests/_CryptoExtrasTests/TestRSAEncryption.swift
+++ b/Tests/_CryptoExtrasTests/TestRSAEncryption.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 import Crypto
 import _CryptoExtras
diff --git a/Tests/_CryptoExtrasTests/TestRSASigning.swift b/Tests/_CryptoExtrasTests/TestRSASigning.swift
index 07da7c127..7bbb2cf1a 100644
--- a/Tests/_CryptoExtrasTests/TestRSASigning.swift
+++ b/Tests/_CryptoExtrasTests/TestRSASigning.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 import Crypto
 import CryptoBoringWrapper
diff --git a/Tests/_CryptoExtrasTests/Utils/BytesUtil.swift b/Tests/_CryptoExtrasTests/Utils/BytesUtil.swift
index 5cc8abc76..4e774b83a 100644
--- a/Tests/_CryptoExtrasTests/Utils/BytesUtil.swift
+++ b/Tests/_CryptoExtrasTests/Utils/BytesUtil.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import XCTest
 
 enum ByteHexEncodingErrors: Error {
diff --git a/Tests/_CryptoExtrasTests/Utils/RFCVector.swift b/Tests/_CryptoExtrasTests/Utils/RFCVector.swift
index 2684a51c0..d4fd55ed5 100644
--- a/Tests/_CryptoExtrasTests/Utils/RFCVector.swift
+++ b/Tests/_CryptoExtrasTests/Utils/RFCVector.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 
 /// This is a not-very-performant decoder of the RFC formatted test vectors.
 ///
diff --git a/Tests/_CryptoExtrasTests/Utils/SplitData.swift b/Tests/_CryptoExtrasTests/Utils/SplitData.swift
index 4b1d19307..040d9cd7a 100644
--- a/Tests/_CryptoExtrasTests/Utils/SplitData.swift
+++ b/Tests/_CryptoExtrasTests/Utils/SplitData.swift
@@ -11,7 +11,11 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 //===----------------------------------------------------------------------===//
+#if canImport(FoundationEssentials)
+import FoundationEssentials
+#else
 import Foundation
+#endif
 import Dispatch
 
 // A testing utility that creates one contiguous and one discontiguous representation of the given Data.