Package: org.conscrypt

Hkdf

public final class Hkdf
Hkdf - perform HKDF key derivation operations per RFC 5869.

Instances should be instantiated using the standard JCA name for the required HMAC.

Each invocation of expand or extract uses a new OpenSSLMac.Hmac instance and so instances of Hkdf are thread-safe.

Constructors

public Hkdf(String hmacName) throws java.security.NoSuchAlgorithmException
Creates an Hkdf instance which will use hmacName as the name for the underlying HMAC algorithm, directly using Conscrypt's OpenSSLMac implementation.

Parameters
hmacName the name of the HMAC algorithm to use
Throws
NoSuchAlgorithmException if hmacName is not a supported HMAC name

Public Methods

getMacLength

public int getMacLength()

extract

public byte[] extract(byte[] salt, byte[] ikm) throws java.security.InvalidKeyException, java.security.NoSuchAlgorithmException
Performs an HKDF extract operation as specified in RFC 5869.
Parameters
salt the salt to use
ikm initial keying material
Returns
byte[] a pseudorandom key suitable for use in expand operations
Throws
InvalidKeyException if the salt is not suitable for use as an HMAC key
NoSuchAlgorithmException if the Mac algorithm is not available

expand

public byte[] expand(byte[] prk, byte[] info, int length) throws java.security.InvalidKeyException, java.security.NoSuchAlgorithmException
Performs an HKDF expand operation as specified in RFC 5869.
Parameters
prk a pseudorandom key of at least HashLen octets, usually the output from the extract step. Where HashLen is the key size of the underlying Mac
info optional context and application specific information, can be zero length
length length of output keying material in bytes ( < = 255*HashLen)
Returns
byte[] output of keying material of length bytes
Throws
InvalidKeyException if prk is not suitable for use as an HMAC key
IllegalArgumentException if length is out of the allowed range
NoSuchAlgorithmException if the Mac algorithm is not available