org.bouncycastle.crypto.encodings

Class ISO9796d1Encoding

Implemented Interfaces:
AsymmetricBlockCipher

public class ISO9796d1Encoding
extends java.lang.Object
implements AsymmetricBlockCipher

ISO 9796-1 padding. Note in the light of recent results you should only use this with RSA (rather than the "simpler" Rabin keys) and you should never use it with anything other than a hash (ie. even if the message is small don't sign the message, sign it's hash) or some "random" value. See your favorite search engine for details.

Constructor Summary

ISO9796d1Encoding(AsymmetricBlockCipher cipher)

Method Summary

int
getInputBlockSize()
return the input block size.
int
getOutputBlockSize()
return the maximum possible size for the output.
int
getPadBits()
retrieve the number of pad bits in the last decoded message.
AsymmetricBlockCipher
getUnderlyingCipher()
void
init(boolean forEncryption, CipherParameters param)
initialise the cipher.
byte[]
processBlock(byte[] in, int inOff, int inLen)
process the block of len bytes stored in in from offset inOff.
void
setPadBits(int padBits)
set the number of bits in the next message to be treated as pad bits.

Constructor Details

ISO9796d1Encoding

public ISO9796d1Encoding(AsymmetricBlockCipher cipher)

Method Details

getInputBlockSize

public int getInputBlockSize()
return the input block size. The largest message we can process is (key_size_in_bits + 3)/16, which in our world comes to key_size_in_bytes / 2.
Specified by:
getInputBlockSize in interface AsymmetricBlockCipher


getOutputBlockSize

public int getOutputBlockSize()
return the maximum possible size for the output.
Specified by:
getOutputBlockSize in interface AsymmetricBlockCipher


getPadBits

public int getPadBits()
retrieve the number of pad bits in the last decoded message.


getUnderlyingCipher

public AsymmetricBlockCipher getUnderlyingCipher()


init

public void init(boolean forEncryption,
                 CipherParameters param)
initialise the cipher.
Specified by:
init in interface AsymmetricBlockCipher

Parameters:
forEncryption - if true the cipher is initialised for encryption, if false for decryption.
param - the key and other data required by the cipher.


processBlock

public byte[] processBlock(byte[] in,
                           int inOff,
                           int inLen)
            throws InvalidCipherTextException
process the block of len bytes stored in in from offset inOff.
Specified by:
processBlock in interface AsymmetricBlockCipher

Parameters:
in - the input data
inOff - offset into the in array where the data starts

Returns:
the resulting byte array of the encryption/decryption process.

Throws:
InvalidCipherTextException - data decrypts improperly.


setPadBits

public void setPadBits(int padBits)
set the number of bits in the next message to be treated as pad bits.