|
public static Decrypt ( byte masterKey, ArraySegment |
||
| masterKey | byte | |
| ciphertext | ArraySegment |
|
| salt | ArraySegment |
|
| counter | uint | |
| return | byte[] | |
}// Decrypt()
public static byte[] Decrypt(byte[] masterKey, ArraySegment<byte> ciphertext, ArraySegment<byte>? salt = null, uint counter = 1)
{
int cipherLength = ciphertext.Count - CONTEXT_BUFFER_LENGTH - MAC_LENGTH;
if (cipherLength < 0) return null;
var bufferSegment = default(ArraySegment<byte>?);
EtM_CTR.Decrypt(masterKey, ciphertext, ref bufferSegment, salt, counter);
return (bufferSegment != null) ? bufferSegment.GetValueOrDefault().Array : null;
}// Decrypt()
public int TransformBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
{
int partialBlockSize = inputCount % EtM_Transform_Constants.OUTPUT_BLOCK_SIZE;
int fullBlockSize = inputCount - partialBlockSize;
if (partialBlockSize != 0)
throw new Exception("inputCount must be a multiple of output block size (" + EtM_Transform_Constants.OUTPUT_BLOCK_SIZE.ToString() + ").");
int i = 0, j = 0;
if (fullBlockSize > 0)
{
var authenticateOnly = this.IsAuthenticateOnly;
for (; i < fullBlockSize; i += EtM_Transform_Constants.OUTPUT_BLOCK_SIZE, j += EtM_Transform_Constants.INPUT_BLOCK_SIZE)
{
var outputSegment = new ArraySegment<byte>?(new ArraySegment<byte>(outputBuffer, outputOffset + j, EtM_Transform_Constants.INPUT_BLOCK_SIZE));
var cipherText = new ArraySegment<byte>(inputBuffer, inputOffset + i, EtM_Transform_Constants.OUTPUT_BLOCK_SIZE);
if (authenticateOnly)
{
if (!EtM_CTR.Authenticate(
masterKey: this.key,
ciphertext: cipherText,
salt: this.salt,
counter: this.currentChunkNumber))
outputSegment = null;
}
else
{
EtM_CTR.Decrypt(
masterKey: this.key,
ciphertext: cipherText,
outputSegment: ref outputSegment,
salt: this.salt,
counter: this.currentChunkNumber);
}
if (outputSegment == null)
{
this.key = null;
throw new CryptographicException("Decryption failed for block " + this.currentChunkNumber.ToString() + ".");
}
if (this.currentChunkNumber == EtM_Transform_Constants.INITIAL_CHUNK_NUMBER)
{
EtM_EncryptTransform.PrependSaltWith1stBlockContext(ref this.salt, inputBuffer, inputOffset);
}
checked { ++this.currentChunkNumber; }
}
}
return j;
}// TransformBlock()
}// TransformBlock()
public byte[] TransformFinalBlock(byte[] inputBuffer, int inputOffset, int inputCount)
{
if (this.key == null) return null; // key would be null if this instance has already been disposed, or previously-called TransformBlock() failed
if (inputCount >= EtM_Transform_Constants.OUTPUT_BLOCK_SIZE)
throw new Exception("Final output block size must be smaller than " + EtM_Transform_Constants.OUTPUT_BLOCK_SIZE.ToString() + ".");
if (inputCount < EtM_Transform_Constants.ETM_CTR_OVERHEAD)
throw new Exception("Final output block size must must be at least " + EtM_Transform_Constants.ETM_CTR_OVERHEAD.ToString() + ".");
byte[] outputBuffer = null;
var cipherText = new ArraySegment<byte>(inputBuffer, inputOffset, inputCount);
if (this.IsAuthenticateOnly)
{
if (EtM_CTR.Authenticate(
masterKey: this.key,
ciphertext: cipherText,
salt: this.salt,
counter: this.currentChunkNumber))
outputBuffer = Array.Empty<byte>();
}
else
{
outputBuffer = EtM_CTR.Decrypt(
masterKey: this.key,
ciphertext: cipherText,
salt: this.salt,
counter: this.currentChunkNumber);
}
this.Dispose();
if (outputBuffer == null)
throw new CryptographicException("Decryption failed for block " + this.currentChunkNumber.ToString() + ".");
this.IsComplete = true;
return outputBuffer;
}// TransformFinalBlock()
public static byte[] Decrypt(byte[] masterKey, ArraySegment<byte> ciphertext, ArraySegment<byte>? salt = null)
{
return EtM_CTR.Decrypt(masterKey, ciphertext, salt);
}
