com.yahoo.security.hpke.Kdf Maven / Gradle / Ivy
// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.security.hpke;
/**
* Key derivation function (KDF)
*
* @author vekterli
*/
public interface Kdf {
/**
* Extract a pseudorandom key of fixed length {@link #nH()} bytes from input keying material
* ikm and an optional byte string salt.
*
* @param salt non-secret salt used as input to KDF
* @param labeledIkm secret input keying material
* @return nH bytes of PRK data
*/
byte[] extract(byte[] salt, byte[] labeledIkm);
/**
* Expand a pseudorandom key prk using optional string info into
* nBytesToExpand bytes of output keying material.
*
* @param prk pseudo random key previously gotten from a call to extract.
* @param info contextual info for expansion; useful for key domain separation
* @param nBytesToExpand number of bytes to return
*
* @return nBytesToExpand bytes of output keying material.
*/
byte[] expand(byte[] prk, byte[] info, int nBytesToExpand);
/** Output size of the extract() function in bytes */
short nH();
/** Predefined KDF ID, as given in RFC 9180 section 7.2 */
short kdfId();
static Kdf hkdfSha256() {
return HkdfSha256.getInstance();
}
}