Example usage for org.bouncycastle.crypto.commitments HashCommitter isRevealed

Introduction

In this page you can find the example usage for org.bouncycastle.crypto.commitments HashCommitter isRevealed.

Prototype

public boolean isRevealed(Commitment commitment, byte[] message) 

Source Link

Document

Return true if the passed in commitment represents a commitment to the passed in message.

Usage

From source file:com.vvote.verifierlibrary.utils.crypto.CryptoUtils.java

License:Open Source License

/**
 * Perform a verification on a hash commitment using bouncy castle. This
 * implementation uses the HashCommitter from bouncy castle and the
 * isRevealed function/*w ww  .j  av  a2 s .c  o  m*/
 * 
 * @param commitment
 * @param witness
 * @param randomValue
 * @return whether the commitment check is successful
 * @throws CommitException
 */
private static boolean bouncyCastleVerifyHashCommitment(byte[] commitment, byte[] witness, byte[] randomValue)
        throws CommitException {

    logger.debug("Verifying hash commitment using Bouncy castle implementation");

    // initialise a hash committer
    HashCommitter hashCommitter = new HashCommitter(new SHA256Digest(), new SecureRandom(witness));

    MessageDigest md = null;

    try {
        logger.debug("Initialising message digest");
        // initialise the message digest
        md = MessageDigest.getInstance(CryptoConstants.Commitments.COMMITMENT_HASH_ALGORITHM);

        // ensure the random value is the correct length
        if (randomValue.length > CryptoConstants.Commitments.RANDOM_VALUE_MAXIMUM_LENGTH) {
            logger.debug("Hashing random value to the correct length");
            md.reset();
            randomValue = md.digest(randomValue);
        }

        // initialise a new Commitment
        Commitment comm = new Commitment(witness, commitment);

        // check whether the given random value opens the commitment
        if (!hashCommitter.isRevealed(comm, randomValue)) {
            logger.error("Bouncy castle hash commitment verification failed");
            return false;
        }

    } catch (NoSuchAlgorithmException e) {
        logger.error("Could not initialise the message digest with the specified algorithm: {}",
                CryptoConstants.Commitments.COMMITMENT_HASH_ALGORITHM, e);
        throw new CommitException("Could not initialise the message digest with the specified algorithm: "
                + CryptoConstants.Commitments.COMMITMENT_HASH_ALGORITHM, e);
    }

    return true;
}

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