text: // randpool.h - originally written and placed in the public domain by Wei Dai
  
  //! \file randpool.h
  //! \brief Class file for Randomness Pool
  //! \details 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.
  //! \details 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).
  //! \details If you need the pre-Crypto++ 5.5 generator then you can find it with:
  //! <pre>
  //!    $ git clone https://github.com/weidai11/cryptopp cryptopp-ancient
  //!    $ cryptopp-ancient
  //!
  //!    # Checkout the RandomPool change
  //!    $ git checkout f41245df6fb9b85574260eca9cd32777e8ab5136
  //!
  //!    # Go back one more
  //!    git checkout HEAD~1
  //!
  //!    $ grep 'MDC<SHA1>' *.h *.cpp
  //!    randpool.cpp:typedef MDC<SHA1> RandomPoolCipher;
  //! </pre>
  //! \since Crypto++ 4.0 (PGP 2.6.x style), Crypto++ 5.5 (AES-256 based)
  
  #ifndef CRYPTOPP_RANDPOOL_H
  #define CRYPTOPP_RANDPOOL_H
  
  #include "cryptlib.h"
  #include "filters.h"
  #include "secblock.h"
  #include "smartptr.h"
  #include "aes.h"
  
  NAMESPACE_BEGIN(CryptoPP)
  
  //! \class RandomPool
  //! \brief Randomness Pool based on AES-256
  //! \details 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.
  //! \details 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).
  //! \since Crypto++ 4.0 (PGP 2.6.x style), Crypto++ 5.5 (AES-256 based)
  class CRYPTOPP_DLL RandomPool : public RandomNumberGenerator, public NotCopyable
  {
  public:
  	//! \brief Construct a RandomPool
  	RandomPool();
  
  	bool CanIncorporateEntropy() const {return true;}
  	void IncorporateEntropy(const byte *input, size_t length);
  	void GenerateIntoBufferedTransformation(BufferedTransformation &target, const std::string &channel, lword size);
  
  	// for backwards compatibility. use RandomNumberSource, RandomNumberStore, and RandomNumberSink for other BufferTransformation functionality
  	void Put(const byte *input, size_t length) {IncorporateEntropy(input, length);}
  
  private:
  	FixedSizeAlignedSecBlock<byte, 16, true> m_seed;
  	FixedSizeAlignedSecBlock<byte, 32> m_key;
  	member_ptr<BlockCipher> m_pCipher;
  	bool m_keySet;
  };
  
  NAMESPACE_END
  
  #endif
  