public static CypherBasedPrngGenerator CreateWithSystemCrngKey(
ICryptoPrimitive cryptoPrimitive = null,
HashAlgorithm hashAlgorithm = null,
CypherCounter initialCounter = null,
int outputBufferSize = -1,
Func <byte[]> additionalEntropyGetter = null)
{
return(Create(new CryptoRandomWrapperGenerator().GetRandomBytes(32), cryptoPrimitive, hashAlgorithm, initialCounter, outputBufferSize, additionalEntropyGetter));
}
public static CypherBasedPrngGenerator CreateWithCheapKey(
ICryptoPrimitive cryptoPrimitive = null,
HashAlgorithm hashAlgorithm = null,
CypherCounter initialCounter = null,
int outputBufferSize = -1,
Func <byte[]> additionalEntropyGetter = null)
{
return(Create(EntropySources.PortableEntropy.Get32(), cryptoPrimitive, hashAlgorithm, initialCounter, outputBufferSize, additionalEntropyGetter));
}
public static CypherBasedPrngGenerator CreateWithNullKey(
ICryptoPrimitive cryptoPrimitive = null,
HashAlgorithm hashAlgorithm = null,
CypherCounter initialCounter = null,
int outputBufferSize = -1,
Func <byte[]> additionalEntropyGetter = null)
{
return(Create(new byte[32], cryptoPrimitive, hashAlgorithm, initialCounter, outputBufferSize, additionalEntropyGetter));
}
/// <summary>
/// Alternate constructor with named parameters.
/// </summary>
public static CypherBasedPrngGenerator Create(byte[] key,
ICryptoPrimitive cryptoPrimitive = null,
HashAlgorithm hashAlgorithm = null,
CypherCounter initialCounter = null,
int outputBufferSize = -1,
Func <byte[]> additionalEntropyGetter = null)
{
return(new CypherBasedPrngGenerator(key,
cryptoPrimitive ?? BlockCypherCryptoPrimitive.Aes256(),
hashAlgorithm ?? SHA512.Create(),
initialCounter ?? new CypherCounter(16),
outputBufferSize < 0 ? 1024 : outputBufferSize,
additionalEntropyGetter));
}
/// <summary>
/// Initialise the CPRNG with the given key material, specified encryption algorithm, initial counter and additional entropy source.
/// </summary>
public CypherBasedPrngGenerator(byte[] key, ICryptoPrimitive cryptoPrimitive, HashAlgorithm hashAlgorithm, CypherCounter initialCounter, int outputBufferSize, Func <byte[]> additionalEntropyGetter)
{
if (key == null)
{
throw new ArgumentNullException(nameof(key));
}
if (cryptoPrimitive == null)
{
throw new ArgumentNullException(nameof(cryptoPrimitive));
}
if (hashAlgorithm == null)
{
throw new ArgumentNullException(nameof(hashAlgorithm));
}
if (initialCounter == null)
{
throw new ArgumentNullException(nameof(initialCounter));
}
_KeySizeInBytes = cryptoPrimitive.KeySizeBytes;
_BlockSizeInBytes = cryptoPrimitive.BlockSizeBytes;
if (!(_KeySizeInBytes == 16 || _KeySizeInBytes == 32 || _KeySizeInBytes == 64))
{
throw new ArgumentOutOfRangeException(nameof(cryptoPrimitive), _KeySizeInBytes, $"Encryption Algorithm KeySize must be 16, 32 or 64 bytes long.");
}
if (!(_BlockSizeInBytes == 16 || _BlockSizeInBytes == 32 || _BlockSizeInBytes == 64))
{
throw new ArgumentOutOfRangeException(nameof(cryptoPrimitive), _BlockSizeInBytes, $"Encryption Algorithm BlockSize must be 16, 32 or 64 bytes long.");
}
if (key.Length != _KeySizeInBytes)
{
throw new ArgumentOutOfRangeException(nameof(key), key.Length, $"Key must be {_KeySizeInBytes} bytes long, based on encryption algorithm used.");
}
if (hashAlgorithm.HashSize / 8 < _KeySizeInBytes)
{
throw new ArgumentOutOfRangeException(nameof(hashAlgorithm), hashAlgorithm.HashSize / 8, $"Hash Algorithm Size must be at least cypher Key Size (${_KeySizeInBytes} bytes).");
}
if (initialCounter.BlockSizeBytes != _BlockSizeInBytes)
{
throw new ArgumentOutOfRangeException(nameof(initialCounter), initialCounter.BlockSizeBytes, $"Counter block size must be equal to Crypto Primitive BlockSize.");
}
_RekeyByteCount = _KeySizeInBytes;
_RekeyBlockCount = (int)Math.Ceiling((double)_RekeyByteCount / (double)_BlockSizeInBytes);
if (outputBufferSize < 0 || outputBufferSize > MaxRequestBytes)
{
throw new ArgumentOutOfRangeException(nameof(outputBufferSize), outputBufferSize, $"Output buffer size must be between 0 and {MaxRequestBytes}. A minimum of {_RekeyByteCount + 64} is required to use the buffer.");
}
// Section 9.4.1 - Initialisation
// Main difference from spec: we accept a key rather than waiting for a Reseed event.
cryptoPrimitive.Key = new byte[_KeySizeInBytes];
_CryptoPrimitive = cryptoPrimitive;
_Counter = initialCounter;
_HashFunction = hashAlgorithm;
// If no getter is supplied, we still create a function, which returns null.
if (additionalEntropyGetter == null)
{
_AdditionalEntropyGetter = () => null;
}
else
{
_AdditionalEntropyGetter = additionalEntropyGetter;
}
// For the output buffer to be usable, it must be at least the re-key size + 32 bytes (enough for several ints).
// The buffer is allocated up front, but not initialised until first call.
_OutputBufferBlockCount = 0;
if (outputBufferSize > _RekeyByteCount + 32)
{
int remainder;
_OutputBufferBlockCount = DivRem(outputBufferSize, _BlockSizeInBytes, out remainder);
if (remainder > 0)
{
_OutputBufferBlockCount = _OutputBufferBlockCount + 1;
}
_OutputBuffer = new byte[_OutputBufferBlockCount + _BlockSizeInBytes];
_OutputBufferIndex = _OutputBuffer.Length;
}
// Difference from spec: re key our cypher immediately with the supplied key.
ReseedInternal(key);
}
/// <summary>
/// Initialise the CPRNG with the given key material, specified encryption algorithm and initial counter.
/// </summary>
public CypherBasedPrngGenerator(byte[] key, ICryptoPrimitive cryptoPrimitive, HashAlgorithm hashAlgorithm, CypherCounter initialCounter, int outputBufferSize)
: this(key, cryptoPrimitive, hashAlgorithm, initialCounter, outputBufferSize, null)
{
}
/// <summary>
/// Initialise the CPRNG with the given key material, specified encryption algorithm and initial counter.
/// </summary>
public CypherBasedPrngGenerator(byte[] key, ICryptoPrimitive cryptoPrimitive, HashAlgorithm hashAlgorithm, CypherCounter initialCounter)
: this(key, cryptoPrimitive, hashAlgorithm, initialCounter, 1024, null)
{
}