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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.security.hpke;
import com.yahoo.security.HKDF;
/**
* KDF implementation using HKDF-SHA256
*
* @author vekterli
*/
final class HkdfSha256 implements Kdf {
private static final HkdfSha256 INSTANCE = new HkdfSha256();
public static HkdfSha256 getInstance() { return INSTANCE; }
@Override
public byte[] extract(byte[] salt, byte[] labeledIkm) {
return ((salt.length != 0) ? HKDF.extractedFrom(salt, labeledIkm)
: HKDF.unsaltedExtractedFrom(labeledIkm))
.pseudoRandomKey();
}
@Override
public byte[] expand(byte[] prk, byte[] info, int nBytesToExpand) {
return HKDF.ofPseudoRandomKey(prk).expand(nBytesToExpand, info);
}
@Override public short nH() { return 32; } // HMAC-SHA256 output size
@Override public short kdfId() { return 0x0001; } // HKDF-SHA256
}
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