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using System;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Security;
namespace Org.BouncyCastle.Crypto.Paddings
{
/**
* A padder that adds Pkcs7/Pkcs5 padding to a block.
*/
public class Pkcs7Padding
: IBlockCipherPadding
{
/**
* Initialise the padder.
*
* @param random - a SecureRandom if available.
*/
public void Init(
SecureRandom random)
{
// nothing to do.
}
/**
* Return the name of the algorithm the cipher implements.
*
* @return the name of the algorithm the cipher implements.
*/
public string PaddingName
{
get { return "PKCS7"; }
}
/**
* add the pad bytes to the passed in block, returning the
* number of bytes added.
*/
public int AddPadding(
byte[] input,
int inOff)
{
byte code = (byte)(input.Length - inOff);
while (inOff < input.Length)
{
input[inOff] = code;
inOff++;
}
return code;
}
/**
* return the number of pad bytes present in the block.
*/
public int PadCount(
byte[] input)
{
int count = (int) input[input.Length - 1];
if (count < 1 || count > input.Length)
{
throw new InvalidCipherTextException("pad block corrupted");
}
for (int i = 1; i <= count; i++)
{
if (input[input.Length - i] != count)
{
throw new InvalidCipherTextException("pad block corrupted");
}
}
return count;
}
}
}
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