public BigInteger getCommitment() {
if (this.commitment != null) {
return this.commitment;
}
H.update(value.toByteArray());
this.randomness = new BigInteger(Util.getModulus().bitLength(), rand);
H.update(this.randomness.toByteArray());
this.commitment = new BigInteger(H.digest()).mod(Util.getModulus());
return this.commitment;
}
/**
* Returns true if the given values match the commitment given.
*
* @param commitment
* @param value
* @param randomness
* @return
*/
public static boolean checkCommitment(
MessageDigest H, BigInteger commitment, BigInteger value, BigInteger randomness) {
H.update(value.toByteArray());
H.update(randomness.toByteArray());
BigInteger testSubject = new BigInteger(H.digest()).mod(Util.getModulus());
return commitment.equals(testSubject);
}