Crypto++  8.8
Free C++ class library of cryptographic schemes
Public Member Functions | List of all members
RandomPool Class Reference

Randomness Pool based on AES-256. More...

+ Inheritance diagram for RandomPool:

Public Member Functions

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

Detailed Description

Randomness Pool based on AES-256.

RandomPool can be used to generate cryptographic quality pseudorandom bytes after seeding the pool with IncorporateEntropy(). Internally, the generator uses AES-256 to produce the stream. Entropy is stirred in using SHA-256.

RandomPool used to follow the design of randpool in PGP 2.6.x. At version 5.5 RandomPool was redesigned to reduce the risk of reusing random numbers after state rollback, which may occur when running in a virtual machine like VMware or a hosted environment.

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

If you need the pre-Crypto++ 5.5 generator then use OldRandomPool class. You should migrate away from OldRandomPool at the earliest opportunity.

See also
Crypto++ 4.0 (PGP 2.6.x style), Crypto++ 5.5 (AES-256 based)

Definition at line 43 of file randpool.h.

Member Function Documentation

◆ CanIncorporateEntropy()

bool RandomPool::CanIncorporateEntropy ( ) const

Determines if a generator can accept additional entropy.

true if IncorporateEntropy() is implemented

Reimplemented from RandomNumberGenerator.

Definition at line 49 of file randpool.h.

◆ IncorporateEntropy()

void RandomPool::IncorporateEntropy ( const byte input,
size_t  length 

Update RNG state with additional unpredictable values.

inputthe entropy to add to the generator
lengththe size of the input buffer

A generator may or may not accept additional entropy. Call CanIncorporateEntropy() to test for the ability to use additional entropy.

If a derived class does not override IncorporateEntropy(), then the base class throws NotImplemented.

Reimplemented from RandomNumberGenerator.

◆ GenerateIntoBufferedTransformation()

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

Generate random bytes into a BufferedTransformation.

targetthe BufferedTransformation object which receives the bytes
channelthe channel on which the bytes should be pumped
lengththe 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.

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

Reimplemented from RandomNumberGenerator.

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