siphash.h

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// siphash.h - written and placed in public domain by Jeffrey Walton.

/// \file siphash.h
/// \brief Classes for SipHash message authentication code
/// \details SipHash computes a 64-bit or 128-bit message authentication code from a variable-length
///   message and 128-bit secret key. It was designed to be efficient even for short inputs, with
///   performance comparable to non-cryptographic hash functions.
/// \details To create a SipHash-2-4 object with a 64-bit MAC use code similar to the following.
///   <pre>  SecByteBlock key(16);
///   prng.GenerateBlock(key, key.size());
///
///   SipHash<2,4,false> hash(key, key.size());
///   hash.Update(...);
///   hash.Final(...);</pre>
/// \details To create a SipHash-2-4 object with a 128-bit MAC use code similar to the following.
///   <pre>  SecByteBlock key(16);
///   prng.GenerateBlock(key, key.size());
///
///   SipHash<2,4,true> hash(key, key.size());
///   hash.Update(...);
///   hash.Final(...);</pre>
/// \sa Jean-Philippe Aumasson and Daniel J. Bernstein <A HREF="http://131002.net/siphash/siphash.pdf">SipHash:
///   a fast short-input PRF</A>
/// \since Crypto++ 6.0

#ifndef CRYPTOPP_SIPHASH_H
#define CRYPTOPP_SIPHASH_H

#include "cryptlib.h"
#include "secblock.h"
#include "seckey.h"
#include "misc.h"

NAMESPACE_BEGIN(CryptoPP)

/// \brief SipHash message authentication code information
/// \tparam T_128bit flag indicating 128-bit (true) versus 64-bit (false) digest size
template <bool T_128bit>
class SipHash_Info : public FixedKeyLength<16>
{
public:
    CRYPTOPP_STATIC_CONSTEXPR const char* StaticAlgorithmName() {return "SipHash";}
    CRYPTOPP_CONSTANT(DIGESTSIZE = (T_128bit ? 16 : 8));
};

/// \brief SipHash message authentication code base class
/// \tparam C the number of compression rounds
/// \tparam D the number of finalization rounds
/// \tparam T_128bit flag indicating 128-bit (true) versus 64-bit (false) digest size
template <unsigned int C, unsigned int D, bool T_128bit>
class SipHash_Base : public MessageAuthenticationCode, public SipHash_Info<T_128bit>
{
public:
    static std::string StaticAlgorithmName() {
        return std::string(SipHash_Info<T_128bit>::StaticAlgorithmName())+"-"+IntToString(C)+"-"+IntToString(D);
    }

    virtual ~SipHash_Base() {}

    SipHash_Base() : m_idx(0) {}

    virtual unsigned int DigestSize() const
        {return SipHash_Info<T_128bit>::DIGESTSIZE;}
    virtual size_t MinKeyLength() const
        {return SipHash_Info<T_128bit>::MIN_KEYLENGTH;}
    virtual size_t MaxKeyLength() const
        {return SipHash_Info<T_128bit>::MAX_KEYLENGTH;}
    virtual size_t DefaultKeyLength() const
        {return SipHash_Info<T_128bit>::DEFAULT_KEYLENGTH;}
    virtual size_t GetValidKeyLength(size_t keylength) const
        {CRYPTOPP_UNUSED(keylength); return SipHash_Info<T_128bit>::DEFAULT_KEYLENGTH;}
    virtual IV_Requirement IVRequirement() const
        {return SimpleKeyingInterface::NOT_RESYNCHRONIZABLE;}
    virtual unsigned int IVSize() const
        {return 0;}
    virtual unsigned int OptimalBlockSize() const
        {return sizeof(word64);}
    virtual unsigned int OptimalDataAlignment () const
        {return GetAlignmentOf<word64>();}

    virtual void Update(const byte *input, size_t length);
    virtual void TruncatedFinal(byte *digest, size_t digestSize);

protected:

    virtual void UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params);
    virtual void Restart();

    inline void SIPROUND()
    {
        m_v[0] += m_v[1];
        m_v[1] = rotlConstant<13>(m_v[1]);
        m_v[1] ^= m_v[0];
        m_v[0] = rotlConstant<32>(m_v[0]);
        m_v[2] += m_v[3];
        m_v[3] = rotlConstant<16>(m_v[3]);
        m_v[3] ^= m_v[2];
        m_v[0] += m_v[3];
        m_v[3] = rotlConstant<21>(m_v[3]);
        m_v[3] ^= m_v[0];
        m_v[2] += m_v[1];
        m_v[1] = rotlConstant<17>(m_v[1]);
        m_v[1] ^= m_v[2];
        m_v[2] = rotlConstant<32>(m_v[2]);
    }

private:
    FixedSizeSecBlock<word64, 4> m_v;
    FixedSizeSecBlock<word64, 2> m_k;
    FixedSizeSecBlock<word64, 2> m_b;

    // Tail bytes
    FixedSizeSecBlock<byte, 8> m_acc;
    size_t m_idx;
};

/// \brief SipHash message authentication code
/// \tparam C the number of compression rounds
/// \tparam D the number of finalization rounds
/// \tparam T_128bit flag indicating 128-bit (true) versus 64-bit (false) digest size
/// \details SipHash computes a 64-bit or 128-bit message authentication code from a variable-length
///   message and 128-bit secret key. It was designed to be efficient even for short inputs, with
///   performance comparable to non-cryptographic hash functions.
/// \details To create a SipHash-2-4 object with a 64-bit MAC use code similar to the following.
///   <pre>  SecByteBlock key(16);
///   prng.GenerateBlock(key, key.size());
///
///   SipHash<2,4,false> hash(key, key.size());
///   hash.Update(...);
///   hash.Final(...);</pre>
/// \details To create a SipHash-2-4 object with a 128-bit MAC use code similar to the following.
///   <pre>  SecByteBlock key(16);
///   prng.GenerateBlock(key, key.size());
///
///   SipHash<2,4,true> hash(key, key.size());
///   hash.Update(...);
///   hash.Final(...);</pre>
/// \sa Jean-Philippe Aumasson and Daniel J. Bernstein <A HREF="http://131002.net/siphash/siphash.pdf">SipHash:
///   a fast short-input PRF</A>
/// \since Crypto++ 6.0
template <unsigned int C=2, unsigned int D=4, bool T_128bit=false>
class SipHash : public SipHash_Base<C, D, T_128bit>
{
public:
    /// \brief Create a SipHash
    SipHash()
        {this->UncheckedSetKey(NULLPTR, 0, g_nullNameValuePairs);}
    /// \brief Create a SipHash
    /// \param key a byte array used to key the cipher
    /// \param length the size of the byte array, in bytes
    SipHash(const byte *key, unsigned int length)
        {this->ThrowIfInvalidKeyLength(length);
         this->UncheckedSetKey(key, length, g_nullNameValuePairs);}
};

template <unsigned int C, unsigned int D, bool T_128bit>
void SipHash_Base<C,D,T_128bit>::Update(const byte *input, size_t length)
{
    CRYPTOPP_ASSERT((input && length) || !length);
    if (!length) return;

    if (m_idx)
    {
        size_t head = STDMIN(size_t(8U-m_idx), length);
        std::memcpy(m_acc+m_idx, input, head);
        m_idx += head; input += head; length -= head;

        if (m_idx == 8)
        {
            word64 m = GetWord<word64>(true, LITTLE_ENDIAN_ORDER, m_acc);
            m_v[3] ^= m;
            for (unsigned int i = 0; i < C; ++i)
                SIPROUND();

            m_v[0] ^= m;
            m_b[0] += 8;

            m_idx = 0;
        }
    }

    while (length >= 8)
    {
        word64 m = GetWord<word64>(false, LITTLE_ENDIAN_ORDER, input);
        m_v[3] ^= m;
        for (unsigned int i = 0; i < C; ++i)
            SIPROUND();

        m_v[0] ^= m;
        m_b[0] += 8;

        input += 8;
        length -= 8;
    }

    CRYPTOPP_ASSERT(length < 8);
    size_t tail = length % 8;
    if (tail)
    {
        std::memcpy(m_acc+m_idx, input, tail);
        m_idx += tail;
    }
}

template <unsigned int C, unsigned int D, bool T_128bit>
void SipHash_Base<C,D,T_128bit>::TruncatedFinal(byte *digest, size_t digestSize)
{
    CRYPTOPP_ASSERT(digest);      // Pointer is valid

    ThrowIfInvalidTruncatedSize(digestSize);

    // The high octet holds length and is digested mod 256
    m_b[0] += m_idx; m_b[0] <<= 56U;
    switch (m_idx)
    {
        case 7:
            m_b[0] |= ((word64)m_acc[6]) << 48;
            // fall through
        case 6:
            m_b[0] |= ((word64)m_acc[5]) << 40;
            // fall through
        case 5:
            m_b[0] |= ((word64)m_acc[4]) << 32;
            // fall through
        case 4:
            m_b[0] |= ((word64)m_acc[3]) << 24;
            // fall through
        case 3:
            m_b[0] |= ((word64)m_acc[2]) << 16;
            // fall through
        case 2:
            m_b[0] |= ((word64)m_acc[1]) << 8;
            // fall through
        case 1:
            m_b[0] |= ((word64)m_acc[0]);
            // fall through
        case 0:
            break;
    }

    m_v[3] ^= m_b[0];

    for (unsigned int i=0; i<C; i++)
        SIPROUND();

    m_v[0] ^= m_b[0];

    if (T_128bit)
        m_v[2] ^= 0xee;
    else
        m_v[2] ^= 0xff;

    for (unsigned int i=0; i<D; i++)
        SIPROUND();

    m_b[0] = m_v[0] ^ m_v[1] ^ m_v[2] ^ m_v[3];
    m_b[0] = ConditionalByteReverse(LITTLE_ENDIAN_ORDER, m_b[0]);

    if (T_128bit)
    {
        m_v[1] ^= 0xdd;
        for (unsigned int i = 0; i<D; ++i)
            SIPROUND();

        m_b[1] = m_v[0] ^ m_v[1] ^ m_v[2] ^ m_v[3];
        m_b[1] = ConditionalByteReverse(LITTLE_ENDIAN_ORDER, m_b[1]);
    }

    memcpy_s(digest, digestSize, m_b.begin(), STDMIN(digestSize, (size_t)SipHash_Info<T_128bit>::DIGESTSIZE));
    Restart();
}

template <unsigned int C, unsigned int D, bool T_128bit>
void SipHash_Base<C,D,T_128bit>::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
{
    CRYPTOPP_UNUSED(params);
    if (key && length)
    {
        m_k[0] = GetWord<word64>(false, LITTLE_ENDIAN_ORDER, key);
        m_k[1] = GetWord<word64>(false, LITTLE_ENDIAN_ORDER, key+8);
    }
    else
    {
        // Avoid Coverity finding
        m_k[0] = m_k[1] = 0;
    }
    Restart();
}

template <unsigned int C, unsigned int D, bool T_128bit>
void SipHash_Base<C,D,T_128bit>::Restart ()
{
    m_v[0] = W64LIT(0x736f6d6570736575);
    m_v[1] = W64LIT(0x646f72616e646f6d);
    m_v[2] = W64LIT(0x6c7967656e657261);
    m_v[3] = W64LIT(0x7465646279746573);

    m_v[3] ^= m_k[1];
    m_v[2] ^= m_k[0];
    m_v[1] ^= m_k[1];
    m_v[0] ^= m_k[0];

    if (T_128bit)
    {
        m_v[1] ^= 0xee;
    }

    m_idx = 0;
    m_b[0] = 0;
}

NAMESPACE_END

#endif // CRYPTOPP_SIPHASH_H