org.bouncycastle.crypto.paddings.X923Padding Maven / Gradle / Ivy
package org.bouncycastle.crypto.paddings;
import java.security.SecureRandom;
import org.bouncycastle.crypto.InvalidCipherTextException;
/**
* A padder that adds X9.23 padding to a block - if a SecureRandom is
* passed in random padding is assumed, otherwise padding with zeros is used.
*/
public class X923Padding
implements BlockCipherPadding
{
SecureRandom random = null;
/**
* Initialise the padder.
*
* @param random a SecureRandom if one is available.
*/
public void init(SecureRandom random)
throws IllegalArgumentException
{
this.random = random;
}
/**
* Return the name of the algorithm the padder implements.
*
* @return the name of the algorithm the padder implements.
*/
public String getPaddingName()
{
return "X9.23";
}
/**
* add the pad bytes to the passed in block, returning the
* number of bytes added.
*/
public int addPadding(
byte[] in,
int inOff)
{
byte code = (byte)(in.length - inOff);
while (inOff < in.length - 1)
{
if (random == null)
{
in[inOff] = 0;
}
else
{
in[inOff] = (byte)random.nextInt();
}
inOff++;
}
in[inOff] = code;
return code;
}
/**
* return the number of pad bytes present in the block.
*/
public int padCount(byte[] in)
throws InvalidCipherTextException
{
int count = in[in.length - 1] & 0xff;
if (count > in.length)
{
throw new InvalidCipherTextException("pad block corrupted");
}
return count;
}
}