/********************************************************************************************
* SHA3-derived function SHAKE
*
* Based on the public domain implementation in crypto_hash/keccakc512/simple/ 
* from http://bench.cr.yp.to/supercop.html by Ronny Van Keer 
* and the public domain "TweetFips202" implementation from https://twitter.com/tweetfips202 
* by Gilles Van Assche, Daniel J. Bernstein, and Peter Schwabe
*
* See NIST Special Publication 800-185 for more information:
* http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-185.pdf
*
*********************************************************************************************/  

#include <stdint.h>
#include <stddef.h>
#include "sikep434r3.h"
#include "sikep434r3_fips202.h"

#define NROUNDS 24
#define ROL(a, offset) ((a << offset) ^ (a >> (64-offset)))

/*************************************************
 * Name:        load64
 *
 * Description: Load 8 bytes into uint64_t in little-endian order
 *
 * Arguments:   - const uint8_t *x: pointer to input byte array
 *
 * Returns the loaded 64-bit unsigned integer
 **************************************************/
static uint64_t load64(const uint8_t *x) {
    uint64_t r = 0;
    for (size_t i = 0; i < 8; ++i) {
        r |= (uint64_t)x[i] << 8 * i;
    }

    return r;
}

/*************************************************
 * Name:        store64
 *
 * Description: Store a 64-bit integer to a byte array in little-endian order
 *
 * Arguments:   - uint8_t *x: pointer to the output byte array
 *              - uint64_t u: input 64-bit unsigned integer
 **************************************************/
static void store64(uint8_t *x, uint64_t u) {
    for (size_t i = 0; i < 8; ++i) {
        x[i] = (uint8_t) (u >> 8 * i);
    }
}

static const uint64_t KeccakF_RoundConstants[NROUNDS] = {
    (uint64_t)0x0000000000000001ULL,
    (uint64_t)0x0000000000008082ULL,
    (uint64_t)0x800000000000808aULL,
    (uint64_t)0x8000000080008000ULL,
    (uint64_t)0x000000000000808bULL,
    (uint64_t)0x0000000080000001ULL,
    (uint64_t)0x8000000080008081ULL,
    (uint64_t)0x8000000000008009ULL,
    (uint64_t)0x000000000000008aULL,
    (uint64_t)0x0000000000000088ULL,
    (uint64_t)0x0000000080008009ULL,
    (uint64_t)0x000000008000000aULL,
    (uint64_t)0x000000008000808bULL,
    (uint64_t)0x800000000000008bULL,
    (uint64_t)0x8000000000008089ULL,
    (uint64_t)0x8000000000008003ULL,
    (uint64_t)0x8000000000008002ULL,
    (uint64_t)0x8000000000000080ULL,
    (uint64_t)0x000000000000800aULL,
    (uint64_t)0x800000008000000aULL,
    (uint64_t)0x8000000080008081ULL,
    (uint64_t)0x8000000000008080ULL,
    (uint64_t)0x0000000080000001ULL,
    (uint64_t)0x8000000080008008ULL,
};

static void KeccakF1600_StatePermute(uint64_t * state)
{
    int round;
    uint64_t Aba, Abe, Abi, Abo, Abu;
    uint64_t Aga, Age, Agi, Ago, Agu;
    uint64_t Aka, Ake, Aki, Ako, Aku;
    uint64_t Ama, Ame, Ami, Amo, Amu;
    uint64_t Asa, Ase, Asi, Aso, Asu;

    /* copyFromState(A, state) */
    Aba = state[ 0];
    Abe = state[ 1];
    Abi = state[ 2];
    Abo = state[ 3];
    Abu = state[ 4];
    Aga = state[ 5];
    Age = state[ 6];
    Agi = state[ 7];
    Ago = state[ 8];
    Agu = state[ 9];
    Aka = state[10];
    Ake = state[11];
    Aki = state[12];
    Ako = state[13];
    Aku = state[14];
    Ama = state[15];
    Ame = state[16];
    Ami = state[17];
    Amo = state[18];
    Amu = state[19];
    Asa = state[20];
    Ase = state[21];
    Asi = state[22];
    Aso = state[23];
    Asu = state[24];

    for( round = 0; round < NROUNDS; round += 2 ) {
        uint64_t BCa, BCe, BCi, BCo, BCu;
        uint64_t Da, De, Di, Do, Du;
        uint64_t Eba, Ebe, Ebi, Ebo, Ebu;
        uint64_t Ega, Ege, Egi, Ego, Egu;
        uint64_t Eka, Eke, Eki, Eko, Eku;
        uint64_t Ema, Eme, Emi, Emo, Emu;
        uint64_t Esa, Ese, Esi, Eso, Esu;

        /* prepareTheta */
        BCa = Aba^Aga^Aka^Ama^Asa;
        BCe = Abe^Age^Ake^Ame^Ase;
        BCi = Abi^Agi^Aki^Ami^Asi;
        BCo = Abo^Ago^Ako^Amo^Aso;
        BCu = Abu^Agu^Aku^Amu^Asu;

        /* thetaRhoPiChiIotaPrepareTheta(round  , A, E) */
        Da = BCu^ROL(BCe, 1);
        De = BCa^ROL(BCi, 1);
        Di = BCe^ROL(BCo, 1);
        Do = BCi^ROL(BCu, 1);
        Du = BCo^ROL(BCa, 1);

        Aba ^= Da;
        BCa = Aba;
        Age ^= De;
        BCe = ROL(Age, 44);
        Aki ^= Di;
        BCi = ROL(Aki, 43);
        Amo ^= Do;
        BCo = ROL(Amo, 21);
        Asu ^= Du;
        BCu = ROL(Asu, 14);
        Eba =   BCa ^((~BCe)&  BCi );
        Eba ^= (uint64_t)KeccakF_RoundConstants[round];
        Ebe =   BCe ^((~BCi)&  BCo );
        Ebi =   BCi ^((~BCo)&  BCu );
        Ebo =   BCo ^((~BCu)&  BCa );
        Ebu =   BCu ^((~BCa)&  BCe );

        Abo ^= Do;
        BCa = ROL(Abo, 28);
        Agu ^= Du;
        BCe = ROL(Agu, 20);
        Aka ^= Da;
        BCi = ROL(Aka,  3);
        Ame ^= De;
        BCo = ROL(Ame, 45);
        Asi ^= Di;
        BCu = ROL(Asi, 61);
        Ega =   BCa ^((~BCe)&  BCi );
        Ege =   BCe ^((~BCi)&  BCo );
        Egi =   BCi ^((~BCo)&  BCu );
        Ego =   BCo ^((~BCu)&  BCa );
        Egu =   BCu ^((~BCa)&  BCe );

        Abe ^= De;
        BCa = ROL(Abe,  1);
        Agi ^= Di;
        BCe = ROL(Agi,  6);
        Ako ^= Do;
        BCi = ROL(Ako, 25);
        Amu ^= Du;
        BCo = ROL(Amu,  8);
        Asa ^= Da;
        BCu = ROL(Asa, 18);
        Eka =   BCa ^((~BCe)&  BCi );
        Eke =   BCe ^((~BCi)&  BCo );
        Eki =   BCi ^((~BCo)&  BCu );
        Eko =   BCo ^((~BCu)&  BCa );
        Eku =   BCu ^((~BCa)&  BCe );

        Abu ^= Du;
        BCa = ROL(Abu, 27);
        Aga ^= Da;
        BCe = ROL(Aga, 36);
        Ake ^= De;
        BCi = ROL(Ake, 10);
        Ami ^= Di;
        BCo = ROL(Ami, 15);
        Aso ^= Do;
        BCu = ROL(Aso, 56);
        Ema =   BCa ^((~BCe)&  BCi );
        Eme =   BCe ^((~BCi)&  BCo );
        Emi =   BCi ^((~BCo)&  BCu );
        Emo =   BCo ^((~BCu)&  BCa );
        Emu =   BCu ^((~BCa)&  BCe );

        Abi ^= Di;
        BCa = ROL(Abi, 62);
        Ago ^= Do;
        BCe = ROL(Ago, 55);
        Aku ^= Du;
        BCi = ROL(Aku, 39);
        Ama ^= Da;
        BCo = ROL(Ama, 41);
        Ase ^= De;
        BCu = ROL(Ase,  2);
        Esa =   BCa ^((~BCe)&  BCi );
        Ese =   BCe ^((~BCi)&  BCo );
        Esi =   BCi ^((~BCo)&  BCu );
        Eso =   BCo ^((~BCu)&  BCa );
        Esu =   BCu ^((~BCa)&  BCe );

        /* prepareTheta */
        BCa = Eba^Ega^Eka^Ema^Esa;
        BCe = Ebe^Ege^Eke^Eme^Ese;
        BCi = Ebi^Egi^Eki^Emi^Esi;
        BCo = Ebo^Ego^Eko^Emo^Eso;
        BCu = Ebu^Egu^Eku^Emu^Esu;

        /* thetaRhoPiChiIotaPrepareTheta(round+1, E, A) */
        Da = BCu^ROL(BCe, 1);
        De = BCa^ROL(BCi, 1);
        Di = BCe^ROL(BCo, 1);
        Do = BCi^ROL(BCu, 1);
        Du = BCo^ROL(BCa, 1);

        Eba ^= Da;
        BCa = Eba;
        Ege ^= De;
        BCe = ROL(Ege, 44);
        Eki ^= Di;
        BCi = ROL(Eki, 43);
        Emo ^= Do;
        BCo = ROL(Emo, 21);
        Esu ^= Du;
        BCu = ROL(Esu, 14);
        Aba =   BCa ^((~BCe)&  BCi );
        Aba ^= (uint64_t)KeccakF_RoundConstants[round+1];
        Abe =   BCe ^((~BCi)&  BCo );
        Abi =   BCi ^((~BCo)&  BCu );
        Abo =   BCo ^((~BCu)&  BCa );
        Abu =   BCu ^((~BCa)&  BCe );

        Ebo ^= Do;
        BCa = ROL(Ebo, 28);
        Egu ^= Du;
        BCe = ROL(Egu, 20);
        Eka ^= Da;
        BCi = ROL(Eka, 3);
        Eme ^= De;
        BCo = ROL(Eme, 45);
        Esi ^= Di;
        BCu = ROL(Esi, 61);
        Aga =   BCa ^((~BCe)&  BCi );
        Age =   BCe ^((~BCi)&  BCo );
        Agi =   BCi ^((~BCo)&  BCu );
        Ago =   BCo ^((~BCu)&  BCa );
        Agu =   BCu ^((~BCa)&  BCe );

        Ebe ^= De;
        BCa = ROL(Ebe, 1);
        Egi ^= Di;
        BCe = ROL(Egi, 6);
        Eko ^= Do;
        BCi = ROL(Eko, 25);
        Emu ^= Du;
        BCo = ROL(Emu, 8);
        Esa ^= Da;
        BCu = ROL(Esa, 18);
        Aka =   BCa ^((~BCe)&  BCi );
        Ake =   BCe ^((~BCi)&  BCo );
        Aki =   BCi ^((~BCo)&  BCu );
        Ako =   BCo ^((~BCu)&  BCa );
        Aku =   BCu ^((~BCa)&  BCe );

        Ebu ^= Du;
        BCa = ROL(Ebu, 27);
        Ega ^= Da;
        BCe = ROL(Ega, 36);
        Eke ^= De;
        BCi = ROL(Eke, 10);
        Emi ^= Di;
        BCo = ROL(Emi, 15);
        Eso ^= Do;
        BCu = ROL(Eso, 56);
        Ama =   BCa ^((~BCe)&  BCi );
        Ame =   BCe ^((~BCi)&  BCo );
        Ami =   BCi ^((~BCo)&  BCu );
        Amo =   BCo ^((~BCu)&  BCa );
        Amu =   BCu ^((~BCa)&  BCe );

        Ebi ^= Di;
        BCa = ROL(Ebi, 62);
        Ego ^= Do;
        BCe = ROL(Ego, 55);
        Eku ^= Du;
        BCi = ROL(Eku, 39);
        Ema ^= Da;
        BCo = ROL(Ema, 41);
        Ese ^= De;
        BCu = ROL(Ese, 2);
        Asa =   BCa ^((~BCe)&  BCi );
        Ase =   BCe ^((~BCi)&  BCo );
        Asi =   BCi ^((~BCo)&  BCu );
        Aso =   BCo ^((~BCu)&  BCa );
        Asu =   BCu ^((~BCa)&  BCe );
    }

    /* copyToState(state, A) */
    state[ 0] = Aba;
    state[ 1] = Abe;
    state[ 2] = Abi;
    state[ 3] = Abo;
    state[ 4] = Abu;
    state[ 5] = Aga;
    state[ 6] = Age;
    state[ 7] = Agi;
    state[ 8] = Ago;
    state[ 9] = Agu;
    state[10] = Aka;
    state[11] = Ake;
    state[12] = Aki;
    state[13] = Ako;
    state[14] = Aku;
    state[15] = Ama;
    state[16] = Ame;
    state[17] = Ami;
    state[18] = Amo;
    state[19] = Amu;
    state[20] = Asa;
    state[21] = Ase;
    state[22] = Asi;
    state[23] = Aso;
    state[24] = Asu;
}

static void keccak_absorb(uint64_t *s, unsigned int r, const unsigned char *m, unsigned long long int mlen,
        unsigned char p)
{
    unsigned long long i;
    unsigned char t[200];

    while (mlen >= r) {
        for (i = 0; i < r / 8; ++i)
            s[i] ^= load64(m + 8 * i);

        KeccakF1600_StatePermute(s);
        mlen -= r;
        m += r;
    }

    for (i = 0; i < r; ++i) {
        t[i] = 0;
    }
    for (i = 0; i < mlen; ++i) {
        t[i] = m[i];
    }

    t[i] = p;
    t[r - 1] |= 128;

    for (i = 0; i < r / 8; ++i) {
        s[i] ^= load64(t + 8 * i);
    }
}

static void keccak_squeezeblocks(unsigned char *h, unsigned long long int nblocks, uint64_t *s, unsigned int r)
{
    unsigned int i;

    while(nblocks > 0) {
        KeccakF1600_StatePermute(s);
        for (i = 0; i < (r>>3); i++) {
            store64(h+8*i, s[i]);
        }

        h += r;
        nblocks--;
    }
}

void shake256(unsigned char *output, unsigned long long outlen, const unsigned char *input,  unsigned long long inlen)
{
    uint64_t s[25];
    unsigned char t[SHAKE256_RATE];
    unsigned long long nblocks = outlen / SHAKE256_RATE;
    size_t i;

    for (i = 0; i < 25; ++i) {
        s[i] = 0;
    }

    /* Absorb input */
    keccak_absorb(s, SHAKE256_RATE, input, inlen, 0x1F);

    /* Squeeze output */
    keccak_squeezeblocks(output, nblocks, s, SHAKE256_RATE);

    output += nblocks * SHAKE256_RATE;
    outlen -= nblocks * SHAKE256_RATE;

    if (outlen) {
        keccak_squeezeblocks(t, 1, s, SHAKE256_RATE);

        for (i = 0; i < outlen; i++) {
            output[i] = t[i];
        }
    }
}