org.spongycastle.crypto.commitments

Class HashCommitter

java.lang.Object

org.spongycastle.crypto.commitments.HashCommitter

All Implemented Interfaces:

Committer

public class HashCommitter
extends java.lang.Object
implements Committer

A basic hash-committer as described in "Making Mix Nets Robust for Electronic Voting by Randomized Partial Checking", by Jakobsson, Juels, and Rivest (11th Usenix Security Symposium, 2002).

Use this class if you can enforce fixed length for messages. If you need something more general, use the GeneralHashCommitter.

Constructor Summary

Constructors

Constructor and Description
HashCommitter(ExtendedDigest digest, java.security.SecureRandom random) Base Constructor.

Method Summary

Modifier and Type	Method and Description
Commitment	commit(byte[] message) Generate a commitment for the passed in message.
boolean	isRevealed(Commitment commitment, byte[] message) Return true if the passed in commitment represents a commitment to the passed in message.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

HashCommitter

public HashCommitter(ExtendedDigest digest,
                     java.security.SecureRandom random)

Base Constructor. The maximum message length that can be committed to is half the length of the internal block size for the digest (ExtendedDigest.getBlockLength()).

Parameters:

digest - digest to use for creating commitments.

random - source of randomness for generating secrets.

Method Detail

commit

public Commitment commit(byte[] message)

Generate a commitment for the passed in message.

Specified by:

commit in interface Committer

Parameters:

message - the message to be committed to,

Returns:

a Commitment

isRevealed

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

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

Specified by:

isRevealed in interface Committer

Parameters:

commitment - a commitment previously generated.

message - the message that was expected to have been committed to.

Returns:

true if commitment matches message, false otherwise.