org.jose4j.jwe.kdf.ConcatKeyDerivationFunction Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of jose4j Show documentation

The jose.4.j library is a robust and easy to use open source implementation of JSON Web Token (JWT) and the JOSE specification suite (JWS, JWE, and JWK). It is written in Java and relies solely on the JCA APIs for cryptography. Please see https://bitbucket.org/b_c/jose4j/wiki/Home for more info, examples, etc..

There is a newer version: 0.9.6

Show newest version

/*
 * Copyright 2012-2015 Brian Campbell
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.jose4j.jwe.kdf;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.jose4j.lang.ByteUtil;
import org.jose4j.lang.UncheckedJoseException;

import java.io.ByteArrayOutputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * An implementation of Concatenation Key Derivation Function (aka Concat KDF or ConcatKDF)
 * from Section 5.8.1 of National Institute of Standards and Technology (NIST),
 * "Recommendation for Pair-Wise Key Establishment Schemes Using Discrete Logarithm Cryptography",
 * NIST Special Publication 800-56A, Revision 2, May 2013.
 */
public class ConcatKeyDerivationFunction
{
    Log log = LogFactory.getLog(this.getClass());

    private int digestLength;
    private MessageDigest messageDigest;

    public ConcatKeyDerivationFunction(String hashAlgoritm)
    {
        messageDigest = getMessageDigest(hashAlgoritm);
        digestLength = ByteUtil.bitLength(messageDigest.getDigestLength());

        log.debug("Hash Algorithm: " + hashAlgoritm + " with hashlen: " + digestLength + " bits");
    }

    public byte[] kdf(byte[] sharedSecret, int keydatalen, byte[] algorithmId, byte[] partyUInfo, byte[] partyVInfo, byte[] suppPubInfo, byte[] suppPrivInfo)
    {
        log.debug("KDF:");
        log.debug("  z: " + ByteUtil.toDebugString(sharedSecret));
        log.debug("  keydatalen: " + keydatalen);
        log.debug("  algorithmId: " + ByteUtil.toDebugString(algorithmId));
        log.debug("  partyUInfo: " + ByteUtil.toDebugString(partyUInfo));
        log.debug("  partyVInfo: " + ByteUtil.toDebugString(partyVInfo));
        log.debug("  suppPubInfo: " + ByteUtil.toDebugString(suppPubInfo));
        log.debug("  suppPrivInfo: " + ByteUtil.toDebugString(suppPrivInfo));

        byte[] otherInfo = ByteUtil.concat(algorithmId, partyUInfo, partyVInfo, suppPubInfo, suppPrivInfo);
        return kdf(sharedSecret, keydatalen, otherInfo);
    }

    public byte[] kdf(byte[] sharedSecret, int keydatalen, byte[] otherInfo)
    {
        long reps = getReps(keydatalen);
        log.debug("reps: " + reps);
        log.debug("otherInfo: " + ByteUtil.toDebugString(otherInfo));

        ByteArrayOutputStream derivedByteOutputStream = new ByteArrayOutputStream();
        for (int i = 1; i <= reps; i++)
        {
            log.debug("rep " + i + " hashing ");
            byte[] counterBytes = ByteUtil.getBytes(i);
            log.debug(" counter: " + ByteUtil.toDebugString(counterBytes));
            log.debug(" z: " + ByteUtil.toDebugString(sharedSecret));
            log.debug(" otherInfo: " + ByteUtil.toDebugString(otherInfo));

            messageDigest.update(counterBytes);
            messageDigest.update(sharedSecret);
            messageDigest.update(otherInfo);
            byte[] digest = messageDigest.digest();
            log.debug(" k("+i+ "): " + ByteUtil.toDebugString(digest));
            derivedByteOutputStream.write(digest, 0, digest.length);
        }

        int keyDateLenInBytes = ByteUtil.byteLength(keydatalen);
        byte[] derivedKeyMaterial = derivedByteOutputStream.toByteArray();
        log.debug("derived key material: " + ByteUtil.toDebugString(derivedKeyMaterial));
        if (derivedKeyMaterial.length != keyDateLenInBytes)
        {
            byte[] newKeyMaterial  = ByteUtil.subArray(derivedKeyMaterial, 0, keyDateLenInBytes);
            log.debug("first "+keydatalen+" bits of derived key material: " + ByteUtil.toDebugString(newKeyMaterial));
            derivedKeyMaterial = newKeyMaterial;
        }

        log.debug("final derived key material: " + ByteUtil.toDebugString(derivedKeyMaterial));
        return derivedKeyMaterial;
    }

    long getReps(int keydatalen)
    {
        double repsD = (float) keydatalen / (float) digestLength;
        repsD = Math.ceil(repsD);
        return (int) repsD;
    }

    private MessageDigest getMessageDigest(String digestMethod)
    {
       try
       {
          return MessageDigest.getInstance(digestMethod);
       }
       catch (NoSuchAlgorithmException e)
       {
           throw new UncheckedJoseException("Must have " + digestMethod + " MessageDigest but don't.", e);
       }
    }
}