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// chacha.h - written and placed in the public domain by Jeffrey Walton.
// Based on Wei Dai's Salsa20, Botan's SSE2 implementation,
// and Bernstein's reference ChaCha family implementation at
// http://cr.yp.to/chacha.html.
/// \file chacha.h
/// \brief Classes for ChaCha8, ChaCha12 and ChaCha20 stream ciphers
/// \details Crypto++ provides Bernstein and ECRYPT's ChaCha from <a href="http://cr.yp.to/chacha/chacha-20080128.pdf">ChaCha,
/// a variant of Salsa20</a> (2008.01.28). Bernstein's implementation is _slightly_ different from the TLS working group's
/// implementation for cipher suites <tt>TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256</tt>,
/// <tt>TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256</tt>, and <tt>TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256</tt>.
/// \since Crypto++ 5.6.4
#ifndef CRYPTOPP_CHACHA_H
#define CRYPTOPP_CHACHA_H
#include "strciphr.h"
#include "secblock.h"
NAMESPACE_BEGIN(CryptoPP)
/// \brief ChaCha stream cipher information
/// \since Crypto++ 5.6.4
struct ChaCha_Info : public VariableKeyLength<32, 16, 32, 16, SimpleKeyingInterface::UNIQUE_IV, 8>
{
/// \brief The algorithm name
/// \returns the algorithm name
/// \details StaticAlgorithmName returns the algorithm's name as a static
/// member function.
/// \details Bernstein named the cipher variants ChaCha8, ChaCha12 and
/// ChaCha20. More generally, Bernstein called the family ChaCha{r}.
/// AlgorithmName() provides the exact name once rounds are set.
static const char* StaticAlgorithmName() {
return "ChaCha";
}
};
/// \brief ChaCha stream cipher implementation
/// \since Crypto++ 5.6.4
class CRYPTOPP_NO_VTABLE ChaCha_Policy : public AdditiveCipherConcretePolicy<word32, 16>
{
public:
~ChaCha_Policy() {}
ChaCha_Policy() : m_rounds(0) {}
protected:
void CipherSetKey(const NameValuePairs ¶ms, const byte *key, size_t length);
void OperateKeystream(KeystreamOperation operation, byte *output, const byte *input, size_t iterationCount);
void CipherResynchronize(byte *keystreamBuffer, const byte *IV, size_t length);
bool CipherIsRandomAccess() const {return true;}
void SeekToIteration(lword iterationCount);
unsigned int GetAlignment() const;
unsigned int GetOptimalBlockSize() const;
std::string AlgorithmName() const;
std::string AlgorithmProvider() const;
// MultiBlockSafe detects a condition that can arise in the SIMD
// implementations where we overflow one of the 32-bit state words
// during addition in an intermediate result. Conditions to trigger
// issue include a user seeks to around 2^32 blocks (256 GB of data).
// https://github.com/weidai11/cryptopp/issues/732
inline bool MultiBlockSafe(unsigned int blocks) const;
FixedSizeAlignedSecBlock<word32, 16> m_state;
unsigned int m_rounds;
};
/// \brief ChaCha stream cipher
/// \details Bernstein and ECRYPT's ChaCha is _slightly_ different from the TLS working
/// group's implementation for cipher suites
/// <tt>TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256</tt>,
/// <tt>TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256</tt>, and
/// <tt>TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256</tt>.
/// \sa <a href="http://cr.yp.to/chacha/chacha-20080208.pdf">ChaCha, a variant of Salsa20</a> (2008.01.28).
/// \since Crypto++ 5.6.4
struct ChaCha : public ChaCha_Info, public SymmetricCipherDocumentation
{
typedef SymmetricCipherFinal<ConcretePolicyHolder<ChaCha_Policy, AdditiveCipherTemplate<> >, ChaCha_Info > Encryption;
typedef Encryption Decryption;
};
NAMESPACE_END
#endif // CRYPTOPP_CHACHA_H
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