org.bouncycastle.crypto.engines

Class RSABlindingEngine

Implemented Interfaces:
AsymmetricBlockCipher

public class RSABlindingEngine
extends java.lang.Object
implements AsymmetricBlockCipher

This does your basic RSA Chaum's blinding and unblinding as outlined in "Handbook of Applied Cryptography", page 475. You need to use this if you are trying to get another party to generate signatures without them being aware of the message they are signing.

Method Summary

int
getInputBlockSize()
Return the maximum size for an input block to this engine.
int
getOutputBlockSize()
Return the maximum size for an output block to this engine.
void
init(boolean forEncryption, CipherParameters param)
Initialise the blinding engine.
byte[]
processBlock(byte[] in, int inOff, int inLen)
Process a single block using the RSA blinding algorithm.

Method Details

getInputBlockSize

public int getInputBlockSize()
Return the maximum size for an input block to this engine. For RSA this is always one byte less than the key size on encryption, and the same length as the key size on decryption.
Specified by:
getInputBlockSize in interface AsymmetricBlockCipher
Returns:
maximum size for an input block.

getOutputBlockSize

public int getOutputBlockSize()
Return the maximum size for an output block to this engine. For RSA this is always one byte less than the key size on decryption, and the same length as the key size on encryption.
Specified by:
getOutputBlockSize in interface AsymmetricBlockCipher
Returns:
maximum size for an output block.

init

public void init(boolean forEncryption,
                 CipherParameters param)
Initialise the blinding engine.
Specified by:
init in interface AsymmetricBlockCipher
Parameters:
forEncryption - true if we are encrypting (blinding), false otherwise.
param - the necessary RSA key parameters.

processBlock

public byte[] processBlock(byte[] in,
                           int inOff,
                           int inLen)
Process a single block using the RSA blinding algorithm.
Specified by:
processBlock in interface AsymmetricBlockCipher
Parameters:
in - the input array.
inOff - the offset into the input buffer where the data starts.
inLen - the length of the data to be processed.
Returns:
the result of the RSA process.