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

#include "pch.h"
#include "config.h"

#include "simon.h"
#include "misc.h"

ANONYMOUS_NAMESPACE_BEGIN

using CryptoPP::word32;
using CryptoPP::word64;
using CryptoPP::rotlFixed;
using CryptoPP::rotrFixed;

//! \brief Round transformation helper
//! \tparam W word type
//! \param v value
template <class W>
inline W f(const W v)
{
    return (rotlFixed(v, 1) & rotlFixed(v, 8)) ^ rotlFixed(v, 2);
}

//! \brief Round transformation
//! \tparam W word type
//! \param x value
//! \param y value
//! \param k value
//! \param l value
template <class W>
inline void R2(W& x, W& y, const W k, const W l)
{
    y ^= f(x); y ^= k;
    x ^= f(y); x ^= l;
}

//! \brief Forward transformation
//! \tparam W word type
//! \tparam R number of rounds
//! \param c output array
//! \param p input array
//! \param k subkey array
template <class W, unsigned int R>
inline void SIMON_Encrypt(W c[2], const W p[2], const W k[R])
{
    c[0]=p[0]; c[1]=p[1];

    // The constexpr residue should allow the optimizer to remove unneeded statements
    if (R%2 == 0)
    {
        for (size_t i = 0; static_cast<int>(i) < R-1; i += 2)
            R2(c[0], c[1], k[i], k[i + 1]);
    }
    else
    {
        for (size_t i = 0; static_cast<int>(i) < R-1; i += 2)
            R2(c[0], c[1], k[i], k[i + 1]);


        c[1] ^= f(c[0]); c[1] ^= k[R-1];
        W t = c[0]; c[0] = c[1]; c[1] = t;
    }
}

//! \brief Reverse transformation
//! \tparam W word type
//! \tparam R number of rounds
//! \param p output array
//! \param c input array
//! \param k subkey array
template <class W, unsigned int R>
inline void SIMON_Decrypt(W p[2], const W c[2], const W k[R])
{
    p[0]=c[0]; p[1]=c[1];

    // The constexpr residue should allow the optimizer to remove unneeded statements
    if (R % 2 == 0)
    {
        for (size_t i = R-2; static_cast<int>(i) >= 0; i -= 2)
            R2(p[1], p[0], k[i+1], k[i]);
    }
    else
    {
        const W t = p[1]; p[1] = p[0];
        p[0] = t; p[1] ^= k[R-1]; p[1] ^= f(p[0]);

        for (size_t i = R-3; static_cast<int>(i) >= 0; i -= 2)
            R2(p[1], p[0], k[i+1], k[i]);
    }
}

//! \brief Subkey generation function
//! \details Used for SIMON-64 with 96-bit key and 42 rounds. A template was
//!   not worthwhile because all instantiations would need specialization.
//! \param key empty subkey array
//! \param k user key array
inline void SPECK64_ExpandKey_42R3K(word32 key[42], const word32 k[3])
{
    const word32 c = 0xfffffffc;
    word64 z = W64LIT(0x7369f885192c0ef5);

    key[0] = k[2]; key[1] = k[1]; key[2] = k[0];
    for (size_t i = 3; i<42; ++i)
    {
        key[i] = c ^ (z & 1) ^ key[i-3] ^ rotrFixed(key[i-1], 3) ^ rotrFixed(key[i-1], 4);
        z >>= 1;
    }
}

//! \brief Subkey generation function
//! \details Used for SIMON-64 with 128-bit key and 44 rounds. A template was
//!   not worthwhile because all instantiations would need specialization.
//! \param key empty subkey array
//! \param k user key array
inline void SPECK64_ExpandKey_44R4K(word32 key[44], const word32 k[4])
{
    const word32 c = 0xfffffffc;
    word64 z = W64LIT(0xfc2ce51207a635db);

    key[0] = k[3]; key[1] = k[2]; key[2] = k[1]; key[3] = k[0];
    for (size_t i = 4; i<44; ++i)
    {
        key[i] = c ^ (z & 1) ^ key[i-4] ^ rotrFixed(key[i-1], 3) ^ key[i-3] ^ rotrFixed(key[i-1], 4) ^ rotrFixed(key[i-3], 1);
        z >>= 1;
    }
}

//! \brief Subkey generation function
//! \details Used for SIMON-128 with 128-bit key and 68 rounds. A template was
//!   not worthwhile because all instantiations would need specialization.
//! \param key empty subkey array
//! \param k user key array
inline void SIMON128_ExpandKey_68R2K(word64 key[68], const word64 k[2])
{
    const word64 c = W64LIT(0xfffffffffffffffc);
    word64 z = W64LIT(0x7369f885192c0ef5);

    key[0] = k[1]; key[1] = k[0];
    for (size_t i=2; i<66; ++i)
    {
        key[i] = c^(z&1)^key[i-2]^rotrFixed(key[i-1],3)^rotrFixed(key[i-1],4);
        z>>=1;
    }

    key[66] = c^1^key[64]^rotrFixed(key[65],3)^rotrFixed(key[65],4);
    key[67] = c^key[65]^rotrFixed(key[66],3)^rotrFixed(key[66],4);
}

//! \brief Subkey generation function
//! \details Used for SIMON-128 with 192-bit key and 69 rounds. A template was
//!   not worthwhile because all instantiations would need specialization.
//! \param key empty subkey array
//! \param k user key array
inline void SIMON128_ExpandKey_69R3K(word64 key[69], const word64 k[3])
{
    const word64 c = W64LIT(0xfffffffffffffffc);
    word64 z = W64LIT(0xfc2ce51207a635db);

    key[0]=k[2]; key[1]=k[1]; key[2]=k[0];
    for (size_t i=3; i<67; ++i)
    {
        key[i] = c^(z&1)^key[i-3]^rotrFixed(key[i-1],3)^rotrFixed(key[i-1],4);
        z>>=1;
    }

    key[67] = c^key[64]^rotrFixed(key[66],3)^rotrFixed(key[66],4);
    key[68] = c^1^key[65]^rotrFixed(key[67],3)^rotrFixed(key[67],4);
}

//! \brief Subkey generation function
//! \details Used for SIMON-128 with 256-bit key and 72 rounds. A template was
//!   not worthwhile because all instantiations would need specialization.
//! \param key empty subkey array
//! \param k user key array
inline void SIMON128_ExpandKey_72R4K(word64 key[72], const word64 k[4])
{
    const word64 c = W64LIT(0xfffffffffffffffc);
    word64 z = W64LIT(0xfdc94c3a046d678b);

    key[0]=k[3]; key[1]=k[2]; key[2]=k[1]; key[3]=k[0];
    for (size_t i=4; i<68; ++i)
    {
        key[i] = c^(z&1)^key[i-4]^rotrFixed(key[i-1],3)^key[i-3]^rotrFixed(key[i-1],4)^rotrFixed(key[i-3],1);
        z>>=1;
    }

    key[68] = c^key[64]^rotrFixed(key[67],3)^key[65]^rotrFixed(key[67],4)^rotrFixed(key[65],1);
    key[69] = c^1^key[65]^rotrFixed(key[68],3)^key[66]^rotrFixed(key[68],4)^rotrFixed(key[66],1);
    key[70] = c^key[66]^rotrFixed(key[69],3)^key[67]^rotrFixed(key[69],4)^rotrFixed(key[67],1);
    key[71] = c^key[67]^rotrFixed(key[70],3)^key[68]^rotrFixed(key[70],4)^rotrFixed(key[68],1);
}

ANONYMOUS_NAMESPACE_END

///////////////////////////////////////////////////////////

NAMESPACE_BEGIN(CryptoPP)

void SIMON64::Base::UncheckedSetKey(const byte *userKey, unsigned int keyLength, const NameValuePairs &params)
{
    CRYPTOPP_ASSERT(keyLength == 12 || keyLength == 16);
    CRYPTOPP_UNUSED(params);

    // Building the key schedule table requires {3,4} words workspace.
    // Encrypting and decrypting requires 4 words workspace.
    m_kwords = keyLength/sizeof(word32);
    m_wspace.New(STDMAX(m_kwords,4U));
    GetUserKey(BIG_ENDIAN_ORDER, m_wspace.begin(), m_kwords, userKey, keyLength);

    switch (m_kwords)
    {
    case 3:
        m_rkey.New(42);
        SPECK64_ExpandKey_42R3K(m_rkey, m_wspace);
        break;
    case 4:
        m_rkey.New(44);
        SPECK64_ExpandKey_44R4K(m_rkey, m_wspace);
        break;
    default:
        CRYPTOPP_ASSERT(0);;
    }
}

void SIMON64::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
    // Reverse bytes on LittleEndian; align pointer on BigEndian
    typedef GetBlock<word32, BigEndian, false> InBlock;
    InBlock iblk(inBlock); iblk(m_wspace[0])(m_wspace[1]);

    switch (m_kwords)
    {
    case 3:
        SIMON_Encrypt<word32, 42>(m_wspace+2, m_wspace+0, m_rkey);
        break;
    case 4:
        SIMON_Encrypt<word32, 44>(m_wspace+2, m_wspace+0, m_rkey);
        break;
    default:
        CRYPTOPP_ASSERT(0);;
    }

    // Reverse bytes on LittleEndian; align pointer on BigEndian
    typedef PutBlock<word32, BigEndian, false> OutBlock;
    OutBlock oblk(xorBlock, outBlock); oblk(m_wspace[2])(m_wspace[3]);
}

void SIMON64::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
    // Reverse bytes on LittleEndian; align pointer on BigEndian
    typedef GetBlock<word32, BigEndian, false> InBlock;
    InBlock iblk(inBlock); iblk(m_wspace[0])(m_wspace[1]);

    switch (m_kwords)
    {
    case 3:
        SIMON_Decrypt<word32, 42>(m_wspace+2, m_wspace+0, m_rkey);
        break;
    case 4:
        SIMON_Decrypt<word32, 44>(m_wspace+2, m_wspace+0, m_rkey);
        break;
    default:
        CRYPTOPP_ASSERT(0);;
    }

    // Reverse bytes on LittleEndian; align pointer on BigEndian
    typedef PutBlock<word32, BigEndian, false> OutBlock;
    OutBlock oblk(xorBlock, outBlock); oblk(m_wspace[2])(m_wspace[3]);
}

///////////////////////////////////////////////////////////

void SIMON128::Base::UncheckedSetKey(const byte *userKey, unsigned int keyLength, const NameValuePairs &params)
{
    CRYPTOPP_ASSERT(keyLength == 16 || keyLength == 24 || keyLength == 32);
    CRYPTOPP_UNUSED(params);

    // Building the key schedule table requires {2,3,4} words workspace.
    // Encrypting and decrypting requires 4 words workspace.
    m_kwords = keyLength/sizeof(word64);
    m_wspace.New(STDMAX(m_kwords,4U));
    GetUserKey(BIG_ENDIAN_ORDER, m_wspace.begin(), m_kwords, userKey, keyLength);

    switch (m_kwords)
    {
    case 2:
        m_rkey.New(68);
        SIMON128_ExpandKey_68R2K(m_rkey, m_wspace);
        break;
    case 3:
        m_rkey.New(69);
        SIMON128_ExpandKey_69R3K(m_rkey, m_wspace);
        break;
    case 4:
        m_rkey.New(72);
        SIMON128_ExpandKey_72R4K(m_rkey, m_wspace);
        break;
    default:
        CRYPTOPP_ASSERT(0);;
    }
}

void SIMON128::Enc::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
    // Reverse bytes on LittleEndian; align pointer on BigEndian
    typedef GetBlock<word64, BigEndian, false> InBlock;
    InBlock iblk(inBlock); iblk(m_wspace[0])(m_wspace[1]);

    switch (m_kwords)
    {
    case 2:
        SIMON_Encrypt<word64, 68>(m_wspace+2, m_wspace+0, m_rkey);
        break;
    case 3:
        SIMON_Encrypt<word64, 69>(m_wspace+2, m_wspace+0, m_rkey);
        break;
    case 4:
        SIMON_Encrypt<word64, 72>(m_wspace+2, m_wspace+0, m_rkey);
        break;
    default:
        CRYPTOPP_ASSERT(0);;
    }

    // Reverse bytes on LittleEndian; align pointer on BigEndian
    typedef PutBlock<word64, BigEndian, false> OutBlock;
    OutBlock oblk(xorBlock, outBlock); oblk(m_wspace[2])(m_wspace[3]);
}

void SIMON128::Dec::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
    // Reverse bytes on LittleEndian; align pointer on BigEndian
    typedef GetBlock<word64, BigEndian, false> InBlock;
    InBlock iblk(inBlock); iblk(m_wspace[0])(m_wspace[1]);

    switch (m_kwords)
    {
    case 2:
        SIMON_Decrypt<word64, 68>(m_wspace+2, m_wspace+0, m_rkey);
        break;
    case 3:
        SIMON_Decrypt<word64, 69>(m_wspace+2, m_wspace+0, m_rkey);
        break;
    case 4:
        SIMON_Decrypt<word64, 72>(m_wspace+2, m_wspace+0, m_rkey);
        break;
    default:
        CRYPTOPP_ASSERT(0);;
    }

    // Reverse bytes on LittleEndian; align pointer on BigEndian
    typedef PutBlock<word64, BigEndian, false> OutBlock;
    OutBlock oblk(xorBlock, outBlock); oblk(m_wspace[2])(m_wspace[3]);
}

NAMESPACE_END