# extract(inputKeyMaterial:salt:) Creates cryptographically strong key material from a main key or passcode that you specify. ``` static func extract(inputKeyMaterial: SymmetricKey, salt: Salt?) -> HashedAuthenticationCode where Salt : DataProtocol ``` ## Parameters `inputKeyMaterial` The main key or passcode the derivation function uses to derive a key. `salt` The salt to use for key derivation. ## Return Value A pseudorandom, cryptographically strong key in the form of a hashed authentication code. ## Discussion Generate a derived symmetric key from the cryptographically strong key material this function creates by calling [`expand(pseudoRandomKey:info:outputByteCount:)`](/documentation/CryptoKit/HKDF/expand(pseudoRandomKey:info:outputByteCount:)). --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)