X917RNG Class Reference

ANSI X9.17 RNG. More...

#include <rng.h>

Inheritance diagram for X917RNG:

Public Member Functions
	X917RNG (BlockTransformation *cipher, const byte *seed, const byte *deterministicTimeVector=NULL)
	Construct a X917RNG.
void	GenerateIntoBufferedTransformation (BufferedTransformation &target, const std::string &channel, lword size)
	Generate random bytes into a BufferedTransformation.
Public Member Functions inherited from RandomNumberGenerator
virtual void	IncorporateEntropy (const byte *input, size_t length)
	Update RNG state with additional unpredictable values.
virtual bool	CanIncorporateEntropy () const
	Determines if a generator can accept additional entropy.
virtual byte	GenerateByte ()
	Generate new random byte and return it.
virtual unsigned int	GenerateBit ()
	Generate new random bit and return it.
virtual word32	GenerateWord32 (word32 min=0, word32 max=0xffffffffUL)
	Generate a random 32 bit word in the range min to max, inclusive.
virtual void	GenerateBlock (byte *output, size_t size)
	Generate random array of bytes.
virtual void	DiscardBytes (size_t n)
	Generate and discard n bytes.
template<class IT >
void	Shuffle (IT begin, IT end)
	Randomly shuffle the specified array.
Public Member Functions inherited from Algorithm
	Algorithm (bool checkSelfTestStatus=true)
	Interface for all crypto algorithms.
virtual std::string	AlgorithmName () const
	Provides the name of this algorithm.
virtual std::string	AlgorithmProvider () const
	Retrieve the provider of this algorithm.
Public Member Functions inherited from Clonable
virtual Clonable *	Clone () const
	Copies this object.

Detailed Description

ANSI X9.17 RNG.

X917RNG is from ANSI X9.17 Appendix C, and it uses a 64-bit block cipher, like TripleDES. If you use a 128-bit block cipher, like AES, then you are effectively using an ANSI X9.31 generator.

You should reseed the generator after a fork() to avoid multiple generators with the same internal state.

See also

AutoSeededX917RNG, DefaultAutoSeededRNG

Definition at line 49 of file rng.h.

Constructor & Destructor Documentation

X917RNG()

X917RNG::X917RNG	(	BlockTransformation *	cipher,
		const byte *	seed,
		const byte *	deterministicTimeVector = NULL
	)

Construct a X917RNG.

Parameters

cipher	the block cipher to use for the generator
seed	a byte buffer to use as a seed
deterministicTimeVector	additional entropy

cipher will be deleted by the destructor. seed must be at least BlockSize() in length. deterministicTimeVector = 0 means obtain time vector from the system.

When constructing a X917RNG, the generator must be keyed or an access violation will occur because the time vector is encrypted using the block cipher. To key the generator during constructions, perform the following:

 SecByteBlock key(AES::DEFAULT_KEYLENGTH), seed(AES::BLOCKSIZE);
 OS_GenerateRandomBlock(false, key, key.size());
 OS_GenerateRandomBlock(false, seed, seed.size());
 X917RNG prng(new AES::Encryption(key, AES::DEFAULT_KEYLENGTH), seed, NULLPTR);

See also

AutoSeededX917RNG

Member Function Documentation

GenerateIntoBufferedTransformation()

void X917RNG::GenerateIntoBufferedTransformation ( BufferedTransformation &  target, const std::string &  channel, lword  length  )

virtual

Generate random bytes into a BufferedTransformation.

Parameters

target	the BufferedTransformation object which receives the bytes
channel	the channel on which the bytes should be pumped
length	the number of bytes to generate

The default implementation calls GenerateBlock() and pumps the result into the DEFAULT_CHANNEL of the target.

All generated values are uniformly distributed over the range specified within the the constraints of a particular generator.

Note

A derived generator must override either GenerateBlock() or GenerateIntoBufferedTransformation(). They can override both, or have one call the other.

Reimplemented from RandomNumberGenerator.

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The documentation for this class was generated from the following file:

• rng.h