}// Encrypt()
public static void Decrypt(byte[] masterKey, ArraySegment<byte> ciphertext, ref ArraySegment<byte>? outputSegment, ArraySegment<byte>? salt = null, uint counter = 1)
{
int cipherLength = ciphertext.Count - CONTEXT_BUFFER_LENGTH - MAC_LENGTH;
if (cipherLength < 0) { outputSegment = null; return; }
try
{
Kdf.SP800_108_Ctr.DeriveKey(hmacFactory: _hmacFactory, key: masterKey, label: salt, context: new ArraySegment<byte>(ciphertext.Array, ciphertext.Offset, CONTEXT_TWEAK_LENGTH), derivedOutput: new ArraySegment<byte>(_sessionKey.Value), counter: counter);
Utils.BlockCopy(_sessionKey.Value, 0, _macKey.Value, 0, MAC_KEY_LENGTH);
using (var hmac = _hmacFactory())
{
hmac.Key = _macKey.Value;
hmac.TransformBlock(ciphertext.Array, ciphertext.Offset + CONTEXT_TWEAK_LENGTH, NONCE_LENGTH + cipherLength, null, 0);
hmac.TransformFinalBlock(ciphertext.Array, 0, 0);
var fullmacActual = hmac.HashInner;
if (!Utils.ConstantTimeEqual(fullmacActual, 0, ciphertext.Array, ciphertext.Offset + ciphertext.Count - MAC_LENGTH, MAC_LENGTH)) { outputSegment = null; return; };
}// using hmac
if (outputSegment == null) outputSegment = (new byte[cipherLength]).AsNullableArraySegment();
Utils.BlockCopy(ciphertext.Array, ciphertext.Offset + CONTEXT_TWEAK_LENGTH, _counterBuffer.Value, 0, NONCE_LENGTH);
Utils.BlockCopy(_sessionKey.Value, MAC_KEY_LENGTH, _encKey.Value, 0, ENC_KEY_LENGTH);
using (var ctrTransform = new Cipher.AesCtrCryptoTransform(key: _encKey.Value, counterBufferSegment: _counterBuffer.Value.AsArraySegment(), aesFactory: _aesFactory))
{
ctrTransform.TransformBlock(inputBuffer: ciphertext.Array, inputOffset: ciphertext.Offset + CONTEXT_BUFFER_LENGTH, inputCount: cipherLength, outputBuffer: outputSegment.GetValueOrDefault().Array, outputOffset: outputSegment.GetValueOrDefault().Offset);
}// using aesDecryptor
}
finally { EtM_CTR.ClearKeyMaterial(); }
}// Decrypt()
public static void Encrypt(byte[] masterKey, ArraySegment<byte> plaintext, byte[] output, int outputOffset, ArraySegment<byte>? salt = null, uint counter = 1)
{
int ciphertextLength = CONTEXT_BUFFER_LENGTH + plaintext.Count + MAC_LENGTH;
if (output.Length - outputOffset < ciphertextLength) throw new ArgumentOutOfRangeException(nameof(output), $"'{nameof(output)}' array segment is not big enough for the ciphertext");
try
{
_cryptoRandom.NextBytes(_contextBuffer.Value);
Kdf.SP800_108_Ctr.DeriveKey(hmacFactory: _hmacFactory, key: masterKey, label: salt, context: new ArraySegment<byte>(_contextBuffer.Value, 0, CONTEXT_TWEAK_LENGTH), derivedOutput: _sessionKey.Value.AsArraySegment(), counter: counter);
Utils.BlockCopy(_sessionKey.Value, 0, _macKey.Value, 0, MAC_KEY_LENGTH);
Utils.BlockCopy(_sessionKey.Value, MAC_KEY_LENGTH, _encKey.Value, 0, ENC_KEY_LENGTH);
Utils.BlockCopy(_contextBuffer.Value, 0, output, outputOffset, CONTEXT_BUFFER_LENGTH);
Utils.BlockCopy(_contextBuffer.Value, CONTEXT_TWEAK_LENGTH, _counterBuffer.Value, 0, NONCE_LENGTH);
using (var ctrTransform = new Cipher.AesCtrCryptoTransform(key: _encKey.Value, counterBufferSegment: _counterBuffer.Value.AsArraySegment(), aesFactory: _aesFactory))
{
ctrTransform.TransformBlock(inputBuffer: plaintext.Array, inputOffset: plaintext.Offset, inputCount: plaintext.Count, outputBuffer: output, outputOffset: outputOffset + CONTEXT_BUFFER_LENGTH);
}// using aesEncryptor
using (var hmac = _hmacFactory())
{
hmac.Key = _macKey.Value;
hmac.TransformBlock(output, outputOffset + CONTEXT_TWEAK_LENGTH, NONCE_LENGTH + plaintext.Count, null, 0);
hmac.TransformFinalBlock(output, 0, 0);
var fullmac = hmac.HashInner;
Utils.BlockCopy(fullmac, 0, output, outputOffset + ciphertextLength - MAC_LENGTH, MAC_LENGTH);
}// using hmac
}
finally { EtM_CTR.ClearKeyMaterial(); }
}// Encrypt()
}// Decrypt()
public static bool Authenticate(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 false;
var encKey = new byte[ENC_KEY_LENGTH];
var macKey = new byte[MAC_KEY_LENGTH];
var sessionKey = new byte[HMAC_LENGTH];
try
{
var ciphertextArray = ciphertext.Array;
var ciphertextOffset = ciphertext.Offset;
Kdf.SP800_108_Ctr.DeriveKey(hmacFactory: _hmacFactory, key: masterKey, label: salt, context: new ArraySegment<byte>(ciphertextArray, ciphertextOffset, CONTEXT_TWEAK_LENGTH), derivedOutput: sessionKey.AsArraySegment(), counter: counter);
//Utils.BlockCopy(sessionKey, 0, macKey, 0, MAC_KEY_LENGTH);
for (int i = 0; i < macKey.Length; ++i) macKey[i] = sessionKey[i];
using (var hmac = _hmacFactory())
{
hmac.Key = macKey;
hmac.TransformBlock(ciphertextArray, ciphertextOffset + CONTEXT_TWEAK_LENGTH, NONCE_LENGTH + cipherLength, null, 0);
hmac.TransformFinalBlock(ciphertextArray, 0, 0);
var fullmacActual = hmac.HashInner;
if (!Utils.ConstantTimeEqual(fullmacActual, 0, ciphertextArray, ciphertextOffset + ciphertext.Count - MAC_LENGTH, MAC_LENGTH)) return false;
}// using hmac
return true;
}
finally { EtM_CTR.ClearKeyMaterial(encKey, macKey, sessionKey); }
}// Authenticate()
public int TransformBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
{
int partialBlockSize = inputCount % EtM_Transform_Constants.INPUT_BLOCK_SIZE;
int fullBlockSize = inputCount - partialBlockSize;
if (partialBlockSize != 0)
throw new Exception("inputCount must be a multiple of input block size (" + EtM_Transform_Constants.INPUT_BLOCK_SIZE.ToString() + ").");
int i = 0, j = 0;
if (fullBlockSize > 0)
{
for (; i < fullBlockSize; i += EtM_Transform_Constants.INPUT_BLOCK_SIZE, j += EtM_Transform_Constants.OUTPUT_BLOCK_SIZE)
{
EtM_CTR.Encrypt(
masterKey: this.key,
plaintext: new ArraySegment<byte>(inputBuffer, inputOffset + i, EtM_Transform_Constants.INPUT_BLOCK_SIZE),
output: outputBuffer,
outputOffset: outputOffset + j,
salt: this.salt,
counter: this.currentChunkNumber);
if (this.currentChunkNumber == EtM_Transform_Constants.INITIAL_CHUNK_NUMBER)
{
EtM_EncryptTransform.PrependSaltWith1stBlockContext(ref this.salt, outputBuffer, outputOffset);
}
checked { ++this.currentChunkNumber; }
}
}
return j;
}// TransformBlock()
}// 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()
}// ClearKeyMaterial()
public static void Encrypt(byte[] masterKey, ArraySegment<byte> plaintext, byte[] output, int outputOffset, ArraySegment<byte>? salt = null, uint counter = 1)
{
int ciphertextLength = CONTEXT_BUFFER_LENGTH + plaintext.Count + MAC_LENGTH;
if (output.Length - outputOffset < ciphertextLength) throw new ArgumentOutOfRangeException(nameof(output), $"'{nameof(output)}' array segment is not big enough for the ciphertext");
var counterBuffer = new byte[Cipher.AesConstants.AES_BLOCK_SIZE];
var contextBuffer = new byte[CONTEXT_BUFFER_LENGTH];
var encKey = new byte[ENC_KEY_LENGTH];
var macKey = new byte[MAC_KEY_LENGTH];
var sessionKey = new byte[HMAC_LENGTH];
try
{
_cryptoRandom.NextBytes(contextBuffer, 0, CONTEXT_BUFFER_LENGTH);
Kdf.SP800_108_Ctr.DeriveKey(hmacFactory: _hmacFactory, key: masterKey, label: salt, context: new ArraySegment<byte>(contextBuffer, 0, CONTEXT_TWEAK_LENGTH), derivedOutput: sessionKey.AsArraySegment(), counter: counter);
//Utils.BlockCopy(sessionKey, 0, macKey, 0, MAC_KEY_LENGTH);
for (int i = 0; i < macKey.Length; ++i) macKey[i] = sessionKey[i];
//Utils.BlockCopy(sessionKey, MAC_KEY_LENGTH, encKey, 0, ENC_KEY_LENGTH);
for (int i = 0; i < encKey.Length; ++i) encKey[i] = sessionKey[MAC_KEY_LENGTH + i];
//Utils.BlockCopy(contextBuffer, 0, output, outputOffset, CONTEXT_BUFFER_LENGTH);
for (int i = 0; i < contextBuffer.Length; ++i) output[outputOffset + i] = contextBuffer[i];
//Utils.BlockCopy(contextBuffer, CONTEXT_TWEAK_LENGTH, counterBuffer, 0, NONCE_LENGTH);
for (int i = 0; i < NONCE_LENGTH; ++i) counterBuffer[i] = contextBuffer[CONTEXT_TWEAK_LENGTH + i];
using (var ctrTransform = new Cipher.AesCtrCryptoTransform(key: encKey, counterBufferSegment: counterBuffer.AsArraySegment(), aesFactory: _aesFactory))
{
ctrTransform.TransformBlock(inputBuffer: plaintext.Array, inputOffset: plaintext.Offset, inputCount: plaintext.Count, outputBuffer: output, outputOffset: outputOffset + CONTEXT_BUFFER_LENGTH);
}// using aesEncryptor
using (var hmac = _hmacFactory())
{
hmac.Key = macKey;
hmac.TransformBlock(output, outputOffset + CONTEXT_TWEAK_LENGTH, NONCE_LENGTH + plaintext.Count, null, 0);
hmac.TransformFinalBlock(output, 0, 0);
var fullmac = hmac.HashInner;
//Utils.BlockCopy(fullmac, 0, output, outputOffset + ciphertextLength - MAC_LENGTH, MAC_LENGTH);
for (int i = 0; i < MAC_LENGTH; ++i) output[outputOffset + ciphertextLength - MAC_LENGTH + i] = fullmac[i];
}// using hmac
}
finally { EtM_CTR.ClearKeyMaterial(encKey, macKey, sessionKey); }
}// Encrypt()
}// Encrypt()
public static void Decrypt(byte[] masterKey, ArraySegment<byte> ciphertext, ref ArraySegment<byte>? outputSegment, ArraySegment<byte>? salt = null, uint counter = 1)
{
int cipherLength = ciphertext.Count - CONTEXT_BUFFER_LENGTH - MAC_LENGTH;
if (cipherLength < 0) { outputSegment = null; return; }
var counterBuffer = new byte[Cipher.AesConstants.AES_BLOCK_SIZE];
var encKey = new byte[ENC_KEY_LENGTH];
var macKey = new byte[MAC_KEY_LENGTH];
var sessionKey = new byte[HMAC_LENGTH];
try
{
var ciphertextArray = ciphertext.Array;
var ciphertextOffset = ciphertext.Offset;
Kdf.SP800_108_Ctr.DeriveKey(hmacFactory: _hmacFactory, key: masterKey, label: salt, context: new ArraySegment<byte>(ciphertextArray, ciphertextOffset, CONTEXT_TWEAK_LENGTH), derivedOutput: sessionKey.AsArraySegment(), counter: counter);
//Utils.BlockCopy(sessionKey, 0, macKey, 0, MAC_KEY_LENGTH);
for (int i = 0; i < macKey.Length; ++i) macKey[i] = sessionKey[i];
using (var hmac = _hmacFactory())
{
hmac.Key = macKey;
hmac.TransformBlock(ciphertextArray, ciphertextOffset + CONTEXT_TWEAK_LENGTH, NONCE_LENGTH + cipherLength, null, 0);
hmac.TransformFinalBlock(ciphertextArray, 0, 0);
var fullmacActual = hmac.HashInner;
if (!Utils.ConstantTimeEqual(fullmacActual, 0, ciphertextArray, ciphertextOffset + ciphertext.Count - MAC_LENGTH, MAC_LENGTH)) { outputSegment = null; return; };
}// using hmac
if (outputSegment == null) outputSegment = (new byte[cipherLength]).AsNullableArraySegment();
//Utils.BlockCopy(ciphertext.Array, ciphertext.Offset + CONTEXT_TWEAK_LENGTH, counterBuffer, 0, NONCE_LENGTH);
for (int i = 0; i < NONCE_LENGTH; ++i) counterBuffer[i] = ciphertextArray[ciphertextOffset + CONTEXT_TWEAK_LENGTH + i];
//Utils.BlockCopy(sessionKey, MAC_KEY_LENGTH, encKey, 0, ENC_KEY_LENGTH);
for (int i = 0; i < encKey.Length; ++i) encKey[i] = sessionKey[MAC_KEY_LENGTH + i];
using (var ctrTransform = new Cipher.AesCtrCryptoTransform(key: encKey, counterBufferSegment: counterBuffer.AsArraySegment(), aesFactory: _aesFactory))
{
ctrTransform.TransformBlock(inputBuffer: ciphertextArray, inputOffset: ciphertextOffset + CONTEXT_BUFFER_LENGTH, inputCount: cipherLength, outputBuffer: outputSegment.GetValueOrDefault().Array, outputOffset: outputSegment.GetValueOrDefault().Offset);
}// using aesDecryptor
}
finally { EtM_CTR.ClearKeyMaterial(encKey, macKey, sessionKey); }
}// Decrypt()
}// 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
if (inputCount >= EtM_Transform_Constants.INPUT_BLOCK_SIZE)
throw new Exception("Final input block size must be smaller than " + EtM_Transform_Constants.INPUT_BLOCK_SIZE.ToString() + ".");
byte[] outputBuffer = new byte[EtM_Transform_Constants.ETM_CTR_OVERHEAD + inputCount];
EtM_CTR.Encrypt(
masterKey: this.key,
plaintext: new ArraySegment<byte>(inputBuffer, inputOffset, inputCount),
output: outputBuffer,
outputOffset: 0,
salt: this.salt,
counter: this.currentChunkNumber);
this.Dispose();
return outputBuffer;
}// TransformFinalBlock()
}// Decrypt()
public static bool Authenticate(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 false;
try
{
Kdf.SP800_108_Ctr.DeriveKey(hmacFactory: _hmacFactory, key: masterKey, label: salt, context: new ArraySegment<byte>(ciphertext.Array, ciphertext.Offset, CONTEXT_TWEAK_LENGTH), derivedOutput: _sessionKey.Value.AsArraySegment(), counter: counter);
Utils.BlockCopy(_sessionKey.Value, 0, _macKey.Value, 0, MAC_KEY_LENGTH);
using (var hmac = _hmacFactory())
{
hmac.Key = _macKey.Value;
hmac.TransformBlock(ciphertext.Array, ciphertext.Offset + CONTEXT_TWEAK_LENGTH, NONCE_LENGTH + cipherLength, null, 0);
hmac.TransformFinalBlock(ciphertext.Array, 0, 0);
var fullmacActual = hmac.HashInner;
if (!Utils.ConstantTimeEqual(fullmacActual, 0, ciphertext.Array, ciphertext.Offset + ciphertext.Count - MAC_LENGTH, MAC_LENGTH)) return false;
}// using hmac
return true;
}
finally { EtM_CTR.ClearKeyMaterial(); }
}// Authenticate()
}// 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 bool Authenticate(byte[] masterKey, ArraySegment<byte> ciphertext, ArraySegment<byte>? salt = null)
{
return EtM_CTR.Authenticate(masterKey, ciphertext, salt);
}
public static byte[] Decrypt(byte[] masterKey, ArraySegment<byte> ciphertext, ArraySegment<byte>? salt = null)
{
return EtM_CTR.Decrypt(masterKey, ciphertext, salt);
}
public static byte[] Encrypt(byte[] masterKey, ArraySegment<byte> plaintext, ArraySegment<byte>? salt = null)
{
return EtM_CTR.Encrypt(masterKey, plaintext, salt);
}
}// Encrypt()
public static byte[] Encrypt(byte[] masterKey, ArraySegment<byte> plaintext, ArraySegment<byte>? salt = null, uint counter = 1)
{
byte[] buffer = new byte[CONTEXT_BUFFER_LENGTH + plaintext.Count + MAC_LENGTH];
EtM_CTR.Encrypt(masterKey: masterKey, plaintext: plaintext, output: buffer, outputOffset: 0, salt: salt, counter: counter);
return buffer;
}// Encrypt()
