/*
* Copyright (c) 2013-2020, The PurpleI2P Project
*
* This file is part of Purple i2pd project and licensed under BSD3
*
* See full license text in LICENSE file at top of project tree
*/

#ifndef GOST_H__
#define GOST_H__

#include <memory>
#include <openssl/ec.h>

namespace i2p {
    namespace crypto {

        // ГОСТ Р 34.10

        enum GOSTR3410ParamSet {
            eGOSTR3410CryptoProA = 0,  // 1.2.643.2.2.35.1
            // XchA = A, XchB = C
            //eGOSTR3410CryptoProXchA, // 1.2.643.2.2.36.0
            //eGOSTR3410CryptoProXchB, // 1.2.643.2.2.36.1
            eGOSTR3410TC26A512,        // 1.2.643.7.1.2.1.2.1
            eGOSTR3410NumParamSets
        };

        class GOSTR3410Curve {
        public:

            GOSTR3410Curve(BIGNUM *a, BIGNUM *b, BIGNUM *p, BIGNUM *q, BIGNUM *x, BIGNUM *y);

            ~GOSTR3410Curve();

            size_t GetKeyLen() const { return m_KeyLen; };

            const EC_GROUP *GetGroup() const { return m_Group; };

            EC_POINT *MulP(const BIGNUM *n) const;

            bool GetXY(const EC_POINT *p, BIGNUM *x, BIGNUM *y) const;

            EC_POINT *CreatePoint(const BIGNUM *x, const BIGNUM *y) const;

            void Sign(const BIGNUM *priv, const BIGNUM *digest, BIGNUM *r, BIGNUM *s);

            bool Verify(const EC_POINT *pub, const BIGNUM *digest, const BIGNUM *r, const BIGNUM *s);

            EC_POINT *
            RecoverPublicKey(const BIGNUM *digest, const BIGNUM *r, const BIGNUM *s, bool isNegativeY = false) const;

        private:

            EC_GROUP *m_Group;
            size_t m_KeyLen; // in bytes
        };

        std::unique_ptr <GOSTR3410Curve> &GetGOSTR3410Curve(GOSTR3410ParamSet paramSet);

// Big Endian
        void GOSTR3411_2012_256(const uint8_t *buf, size_t len, uint8_t *digest);

        void GOSTR3411_2012_512(const uint8_t *buf, size_t len, uint8_t *digest);

// Little Endian
        struct GOSTR3411_2012_CTX;

        GOSTR3411_2012_CTX *GOSTR3411_2012_CTX_new();

        void GOSTR3411_2012_CTX_Init(GOSTR3411_2012_CTX *ctx, bool is512 = true);

        void GOSTR3411_2012_CTX_Update(const uint8_t *buf, size_t len, GOSTR3411_2012_CTX *ctx);

        void GOSTR3411_2012_CTX_Finish(uint8_t *digest, GOSTR3411_2012_CTX *ctx);

        void GOSTR3411_2012_CTX_free(GOSTR3411_2012_CTX *ctx);
    }
}

#endif