/*************************************************************************
* Copyright (C) 2016 Intel Corporation
*
* Licensed under the Apache License,  Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* 	http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law  or agreed  to  in  writing,  software
* distributed under  the License  is  distributed  on  an  "AS IS"  BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the  specific  language  governing  permissions  and
* limitations under the License.
*************************************************************************/

/*
//     Intel(R) Cryptography Primitives Library
//     GF(p^d) methods, if binomial generator
//
*/
#include "owncp.h"
#include "owndefs.h"

#include "gfpec/pcpgfpxstuff.h"
#include "gfpec/pcpgfpxmethod_com.h"
#include "gfpec/pcpgfpxmethod_binom_epid2.h"

//tbcd: temporary excluded: #include <assert.h>

/*
// Intel(R) Enhanced Privacy ID (Intel(R) EPID) 2.0 specific.
//
// Intel(R) EPID 2.0 uses the following finite field hierarchy:
//
// 1) prime field GF(p),
//    p = 0xFFFFFFFFFFFCF0CD46E5F25EEE71A49F0CDC65FB12980A82D3292DDBAED33013
//
// 2) 2-degree extension of GF(p): GF(p^2) == GF(p)[x]/g(x), g(x) = x^2 -beta,
//    beta =-1 mod p, so "beta" represents as {1}
//
// 3) 3-degree extension of GF(p^2) ~ GF(p^6): GF((p^2)^3) == GF(p)[v]/g(v), g(v) = v^3 -xi,
//    xi belongs GF(p^2), xi=x+2, so "xi" represents as {2,1} ---- "2" is low- and "1" is high-order coefficients
//
// 4) 2-degree extension of GF((p^2)^3) ~ GF(p^12): GF(((p^2)^3)^2) == GF(p)[w]/g(w), g(w) = w^2 -vi,
//    psi belongs GF((p^2)^3), vi=0*v^2 +1*v +0, so "vi" represents as {0,1,0}---- "0", '1" and "0" are low-, middle- and high-order coefficients
//
// See representations in t_gfpparam.cpp
//
*/

/*
// Multiplication case: mul(a, vi) over GF((p^2)^3),
// where:
//    a, belongs to GF((p^2)^3)
//    xi belongs to GF((p^2)^3), vi={0,1,0}
//
// The case is important in GF(((p^2)^3)^2) arithmetic for Intel(R) EPID 2.0.
//
*/
IPPCP_INLINE BNU_CHUNK_T* cpFq6Mul_vi(BNU_CHUNK_T* pR, const BNU_CHUNK_T* pA, gsEngine* pGFEx)
{
    gsEngine* pGroundGFE = GFP_PARENT(pGFEx);
    int termLen          = GFP_FELEN(pGroundGFE);

    const BNU_CHUNK_T* pA0 = pA;
    const BNU_CHUNK_T* pA1 = pA + termLen;
    const BNU_CHUNK_T* pA2 = pA + termLen * 2;
    BNU_CHUNK_T* pR0       = pR;
    BNU_CHUNK_T* pR1       = pR + termLen;
    BNU_CHUNK_T* pR2       = pR + termLen * 2;

    BNU_CHUNK_T* t = cpGFpGetPool(1, pGroundGFE);
    //tbcd: temporary excluded: assert(NULL!=t);

    cpFq2Mul_xi(t, pA2, pGroundGFE);
    cpGFpElementCopy(pR2, pA1, termLen);
    cpGFpElementCopy(pR1, pA0, termLen);
    cpGFpElementCopy(pR0, t, termLen);

    cpGFpReleasePool(1, pGroundGFE);

    return pR;
}

/*
// Intel(R) EPID 2.0 specific
// ~~~~~~~~~~~~~~~
//
// Multiplication over GF(p^2)
//    - field polynomial: g(x) = x^2 - beta  => binominal with specific value of "beta"
//    - beta = p-1
//
// Multiplication over GF(((p^2)^3)^2)    ~ GF(p^12)
//    - field polynomial: g(w) = w^2 - vi   => binominal with specific value of "vi"
//    - vi = 0*v^2 + 1*v + 0 - i.e vi={0,1,0} belongs to GF((p^2)^3)
*/
/* clang-format off */
IPP_OWN_DEFN(static BNU_CHUNK_T*, cpGFpxMul_p2_binom_epid2, (BNU_CHUNK_T* pR,
                                                             const BNU_CHUNK_T* pA,
                                                             const BNU_CHUNK_T* pB,
                                                             gsEngine* pGFEx))
/* clang-format on */
{
    gsEngine* pGroundGFE = GFP_PARENT(pGFEx);
    mod_mul mulF         = GFP_METHOD(pGroundGFE)->mul;
    mod_add addF         = GFP_METHOD(pGroundGFE)->add;
    mod_sub subF         = GFP_METHOD(pGroundGFE)->sub;

    int groundElemLen = GFP_FELEN(pGroundGFE);

    const BNU_CHUNK_T* pA0 = pA;
    const BNU_CHUNK_T* pA1 = pA + groundElemLen;

    const BNU_CHUNK_T* pB0 = pB;
    const BNU_CHUNK_T* pB1 = pB + groundElemLen;

    BNU_CHUNK_T* pR0 = pR;
    BNU_CHUNK_T* pR1 = pR + groundElemLen;

    BNU_CHUNK_T* t0 = cpGFpGetPool(4, pGroundGFE);
    BNU_CHUNK_T* t1 = t0 + groundElemLen;
    BNU_CHUNK_T* t2 = t1 + groundElemLen;
    BNU_CHUNK_T* t3 = t2 + groundElemLen;
    //tbcd: temporary excluded: assert(NULL!=t0);

    mulF(t0, pA0, pB0, pGroundGFE); /* t0 = a[0]*b[0] */
    mulF(t1, pA1, pB1, pGroundGFE); /* t1 = a[1]*b[1] */
    addF(t2, pA0, pA1, pGroundGFE); /* t2 = a[0]+a[1] */
    addF(t3, pB0, pB1, pGroundGFE); /* t3 = b[0]+b[1] */

    mulF(pR1, t2, t3, pGroundGFE);  /* r[1] = (a[0]+a[1]) * (b[0]+b[1]) */
    subF(pR1, pR1, t0, pGroundGFE); /* r[1] -= a[0]*b[0]) + a[1]*b[1] */
    subF(pR1, pR1, t1, pGroundGFE);

    /* Intel(R) EPID 2.0 specific */
    {
        int basicExtDegree = cpGFpBasicDegreeExtension(pGFEx);

        /* deal with GF(p^2) */
        if (basicExtDegree == 2) {
            subF(pR0, t0, t1, pGroundGFE);
        }
        /* deal with GF(p^6^2) */
        else if (basicExtDegree == 12) {
            cpFq6Mul_vi(t1, t1, pGroundGFE);
            addF(pR0, t0, t1, pGroundGFE);
        }
        /* deal with GF(p^x^2) - it's not Intel(R) EPID 2.0 case, just a case */
        else {
            cpGFpxMul_G0(t1, t1, pGFEx);
            subF(pR0, t0, t1, pGroundGFE);
        }
    }

    cpGFpReleasePool(4, pGroundGFE);
    return pR;
}

/*
// Intel(R) EPID 2.0 specific
// ~~~~~~~~~~~~~~~
//
// Squaring over GF(p^2)
//    - field polynomial: g(x) = x^2 - beta  => binominal with specific value of "beta"
//    - beta = p-1
//
// Squaring in GF(((p^2)^3)^2)      ~ GF(p^12)
//    - field polynomial: g(w) = w^2 - vi   => binominal with specific value of "vi"
//    - vi = 0*v^2 + 1*v + 0 - i.e vi={0,1,0} belongs to GF((p^2)^3)
*/
/* clang-format off */
IPP_OWN_DEFN(static BNU_CHUNK_T*, cpGFpxSqr_p2_binom_epid2, (BNU_CHUNK_T* pR,
                                                             const BNU_CHUNK_T* pA,
                                                             gsEngine* pGFEx))
/* clang-format on */
{
    gsEngine* pGroundGFE = GFP_PARENT(pGFEx);
    mod_mul mulF         = GFP_METHOD(pGroundGFE)->mul;
    mod_sqr sqrF         = GFP_METHOD(pGroundGFE)->sqr;
    mod_add addF         = GFP_METHOD(pGroundGFE)->add;
    mod_sub subF         = GFP_METHOD(pGroundGFE)->sub;

    int groundElemLen = GFP_FELEN(pGroundGFE);

    const BNU_CHUNK_T* pA0 = pA;
    const BNU_CHUNK_T* pA1 = pA + groundElemLen;

    BNU_CHUNK_T* pR0 = pR;
    BNU_CHUNK_T* pR1 = pR + groundElemLen;

    BNU_CHUNK_T* t0 = cpGFpGetPool(3, pGroundGFE);
    BNU_CHUNK_T* t1 = t0 + groundElemLen;
    BNU_CHUNK_T* u0 = t1 + groundElemLen;
    //tbcd: temporary excluded: assert(NULL!=t0);

    mulF(u0, pA0, pA1, pGroundGFE); /* u0 = a[0]*a[1] */

    /* Intel(R) EPID 2.0 specific */
    {
        int basicExtDegree = cpGFpBasicDegreeExtension(pGFEx);

        /* deal with GF(p^2) */
        if (basicExtDegree == 2) {
            addF(t0, pA0, pA1, pGroundGFE);
            subF(t1, pA0, pA1, pGroundGFE);
            mulF(pR0, t0, t1, pGroundGFE);
            addF(pR1, u0, u0, pGroundGFE); /* r[1] = 2*a[0]*a[1] */
        }
        /* deal with GF(p^6^2) */
        else if (basicExtDegree == 12) {
            subF(t0, pA0, pA1, pGroundGFE);
            cpFq6Mul_vi(t1, pA1, pGroundGFE);
            subF(t1, pA0, t1, pGroundGFE);
            mulF(t0, t0, t1, pGroundGFE);
            addF(t0, t0, u0, pGroundGFE);
            cpFq6Mul_vi(t1, u0, pGroundGFE);
            addF(pR0, t0, t1, pGroundGFE);
            addF(pR1, u0, u0, pGroundGFE);
        }
        /* just a case */
        else {
            sqrF(t0, pA0, pGroundGFE);     /* t0 = a[0]*a[0] */
            sqrF(t1, pA1, pGroundGFE);     /* t1 = a[1]*a[1] */
            cpGFpxMul_G0(t1, t1, pGFEx);
            subF(pR0, t0, t1, pGroundGFE);
            addF(pR1, u0, u0, pGroundGFE); /* r[1] = 2*a[0]*a[1] */
        }
    }

    cpGFpReleasePool(3, pGroundGFE);
    return pR;
}

/*
// return specific polynomi alarith methods
// polynomial - deg 2 binomial (Intel(R) EPID 2.0)
*/
static gsModMethod* gsPolyArith_binom2_epid2(void)
{
    static gsModMethod m = {
        cpGFpxEncode_com,
        cpGFpxDecode_com,
        cpGFpxMul_p2_binom_epid2,
        cpGFpxSqr_p2_binom_epid2,
        NULL,
        cpGFpxAdd_com,
        cpGFpxSub_com,
        cpGFpxNeg_com,
        cpGFpxDiv2_com,
        cpGFpxMul2_com,
        cpGFpxMul3_com,
        //cpGFpxInv
    };
    return &m;
}

/*F*
// Name: ippsGFpxMethod_binom2_epid2
//
// Purpose: Returns a reference to the implementation of arithmetic operations over GF(pd).
//
// Returns:          pointer to a structure containing
//                   an implementation of arithmetic operations over GF(pd)
//                   g(x) = x^2 - a0, a0 from GF(q), a0 = 1
//                   g(w) = w^2 - V0, v0 from GF((q^2)^3), V0 = 0*s^2 + v + 0
//
//
*F*/

IPPFUN(const IppsGFpMethod*, ippsGFpxMethod_binom2_epid2, (void))
{
    /* Prevents re-initialization for better multi-threaded/repeated call performance */
    static volatile int isInitialized = 0;

    static IppsGFpMethod method = { cpID_Binom2_epid20, 2, NULL, NULL, NULL };
    if (isInitialized) {
        CP_PREVENT_REORDER();
        return &method;
    }

    method.arith = gsPolyArith_binom2_epid2();

    CP_PREVENT_REORDER();
    isInitialized = 1;

    return &method;
}
