From d4d418503f20739e14cd00852b7ff0770b22b501 Mon Sep 17 00:00:00 2001
From: Jeffrey Walton <noloader@gmail.com>
Date: Thu, 21 Apr 2016 12:08:21 -0400
Subject: [PATCH] Add ChaCha family of stream ciphers

---
 chacha.h | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 chacha.h

diff --git a/chacha.h b/chacha.h
new file mode 100644
index 00000000..9a07467a
--- /dev/null
+++ b/chacha.h
@@ -0,0 +1,67 @@
+// chacha.h - written and placed in the public domain by Jeffrey Walton.
+//            Copyright assigned to the Crypto++ project.
+
+//! \file chacha.h
+//! \brief Classes for ChaCha8, ChaCha12 and ChaCha stream ciphers
+
+#ifndef CRYPTOPP_CHACHA_H
+#define CRYPTOPP_CHACHA_H
+
+#include "strciphr.h"
+#include "secblock.h"
+
+NAMESPACE_BEGIN(CryptoPP)
+
+//! \class ChaCha_Info
+//! \brief ChaCha stream cipher information
+template <unsigned int R>
+struct ChaCha_Info : public VariableKeyLength<32, 16, 32, 16, SimpleKeyingInterface::UNIQUE_IV, 8>, public FixedRounds<R>
+{
+	static const char *StaticAlgorithmName() {return "ChaCha";}
+};
+
+template <unsigned int R>
+class CRYPTOPP_NO_VTABLE ChaCha_Base : public AdditiveCipherConcretePolicy<word32, 16>
+{
+protected:
+	void CipherSetKey(const NameValuePairs &params, 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;
+
+	FixedSizeAlignedSecBlock<word32, 16> m_state;
+};
+
+//! \class ChaCha8
+//! \brief ChaCha8 stream cipher
+//! \sa <a href="http://cr.yp.to/chacha/chacha-20080128.pdf">ChaCha, a variant of Salsa20</a> (2008.01.28).
+struct ChaCha8 : public ChaCha_Info<8>, public SymmetricCipherDocumentation
+{
+	typedef SymmetricCipherFinal<ConcretePolicyHolder<ChaCha_Base<8>, AdditiveCipherTemplate<> >, ChaCha_Info<8> > Encryption;
+	typedef SymmetricCipherFinal<ConcretePolicyHolder<ChaCha_Base<8>, AdditiveCipherTemplate<> >, ChaCha_Info<8> > Decryption;
+};
+
+//! \class ChaCha12
+//! \brief ChaCha12 stream cipher
+//! \sa <a href="http://cr.yp.to/chacha/chacha-20080128.pdf">ChaCha, a variant of Salsa20</a> (2008.01.28).
+struct ChaCha12 : public ChaCha_Info<12>, public SymmetricCipherDocumentation
+{
+	typedef SymmetricCipherFinal<ConcretePolicyHolder<ChaCha_Base<12>, AdditiveCipherTemplate<> >, ChaCha_Info<12> > Encryption;
+	typedef SymmetricCipherFinal<ConcretePolicyHolder<ChaCha_Base<12>, AdditiveCipherTemplate<> >, ChaCha_Info<12> > Decryption;
+};
+
+//! \class ChaCha20
+//! \brief ChaCha20 stream cipher
+//! \sa <a href="http://cr.yp.to/chacha/chacha-20080128.pdf">ChaCha, a variant of Salsa20</a> (2008.01.28).
+struct ChaCha20 : public ChaCha_Info<20>, public SymmetricCipherDocumentation
+{
+	typedef SymmetricCipherFinal<ConcretePolicyHolder<ChaCha_Base<20>, AdditiveCipherTemplate<> >, ChaCha_Info<20> > Encryption;
+	typedef SymmetricCipherFinal<ConcretePolicyHolder<ChaCha_Base<20>, AdditiveCipherTemplate<> >, ChaCha_Info<20> > Decryption;
+};
+
+NAMESPACE_END
+
+#endif  // CRYPTOPP_CHACHA_H