CtrCipherMode
Implements CTR cipher mode
using System;
using System.Globalization;
namespace Renci.SshNet.Security.Cryptography.Ciphers.Modes
{
public class CtrCipherMode : CipherMode
{
private readonly byte[] _ivOutput;
public CtrCipherMode(byte[] iv)
: base(iv)
{
_ivOutput = new byte[iv.Length];
}
public override int EncryptBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
{
if (inputBuffer.Length - inputOffset < _blockSize)
throw new ArgumentException("Invalid input buffer");
if (outputBuffer.Length - outputOffset < _blockSize)
throw new ArgumentException("Invalid output buffer");
if (inputCount != _blockSize)
throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, "inputCount must be {0}.", _blockSize));
Cipher.EncryptBlock(IV, 0, IV.Length, _ivOutput, 0);
for (int i = 0; i < _blockSize; i++) {
outputBuffer[outputOffset + i] = (byte)(_ivOutput[i] ^ inputBuffer[inputOffset + i]);
}
int num = IV.Length;
while (--num >= 0 && ++IV[num] == 0) {
}
return _blockSize;
}
public override int DecryptBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
{
if (inputBuffer.Length - inputOffset < _blockSize)
throw new ArgumentException("Invalid input buffer");
if (outputBuffer.Length - outputOffset < _blockSize)
throw new ArgumentException("Invalid output buffer");
if (inputCount != _blockSize)
throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, "inputCount must be {0}.", _blockSize));
Cipher.EncryptBlock(IV, 0, IV.Length, _ivOutput, 0);
for (int i = 0; i < _blockSize; i++) {
outputBuffer[outputOffset + i] = (byte)(_ivOutput[i] ^ inputBuffer[inputOffset + i]);
}
int num = IV.Length;
while (--num >= 0 && ++IV[num] == 0) {
}
return _blockSize;
}
}
}