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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.4. Note: this package includes the NTRU encryption algorithms.
package org.bouncycastle.crypto.paddings;
import java.security.SecureRandom;
import org.bouncycastle.crypto.InvalidCipherTextException;
/**
* A padder that adds the padding according to the scheme referenced in
* ISO 7814-4 - scheme 2 from ISO 9797-1. The first byte is 0x80, rest is 0x00
*/
public class ISO7816d4Padding
implements BlockCipherPadding
{
/**
* Initialise the padder.
*
* @param random - a SecureRandom if available.
*/
public void init(SecureRandom random)
throws IllegalArgumentException
{
// nothing to do.
}
/**
* Return the name of the algorithm the padder implements.
*
* @return the name of the algorithm the padder implements.
*/
public String getPaddingName()
{
return "ISO7816-4";
}
/**
* add the pad bytes to the passed in block, returning the
* number of bytes added.
*/
public int addPadding(
byte[] in,
int inOff)
{
int added = (in.length - inOff);
in [inOff]= (byte) 0x80;
inOff ++;
while (inOff < in.length)
{
in[inOff] = (byte) 0;
inOff++;
}
return added;
}
/**
* return the number of pad bytes present in the block.
*/
public int padCount(byte[] in)
throws InvalidCipherTextException
{
int position = -1, still00Mask = -1;
int i = in.length;
while (--i >= 0)
{
int next = in[i] & 0xFF;
int match00Mask = ((next ^ 0x00) - 1) >> 31;
int match80Mask = ((next ^ 0x80) - 1) >> 31;
position ^= (i ^ position) & (still00Mask & match80Mask);
still00Mask &= match00Mask;
}
if (position < 0)
{
throw new InvalidCipherTextException("pad block corrupted");
}
return in.length - position;
}
}