org.bouncycastle.crypto.commitments
Class GeneralHashCommitter

java.lang.Object
  |
  +--org.bouncycastle.crypto.commitments.GeneralHashCommitter

All Implemented Interfaces:

Committer

public class GeneralHashCommitter

extends java.lang.Object

implements Committer

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

The algorithm used by this class differs from the one given in that it includes the length of the message in the hash calculation.

Constructor Summary

GeneralHashCommitter(ExtendedDigest digest, java.security.SecureRandom random)
Base Constructor.

Method Summary

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

GeneralHashCommitter

public GeneralHashCommitter(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.