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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 1.5 to JDK 1.8.
package org.bouncycastle.crypto.paddings;
import java.security.SecureRandom;
import org.bouncycastle.crypto.InvalidCipherTextException;
/**
* A padder that adds PKCS7/PKCS5 padding to a block.
*/
public class PKCS7Padding
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 "PKCS7";
}
/**
* 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)
{
in[inOff] = code;
inOff++;
}
return code;
}
/**
* return the number of pad bytes present in the block.
*/
public int padCount(byte[] in)
throws InvalidCipherTextException
{
byte countAsByte = in[in.length - 1];
int count = countAsByte & 0xFF;
int position = in.length - count;
int failed = (position | (count - 1)) >> 31;
for (int i = 0; i < in.length; ++i)
{
failed |= (in[i] ^ countAsByte) & ~((i - position) >> 31);
}
if (failed != 0)
{
throw new InvalidCipherTextException("pad block corrupted");
}
return count;
}
}
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