/*

* Elliptic curves over GF(p)

*

* (C) 2007 Martin Doering, Christoph Ludwig, Falko Strenzke

*     2010-2011,2012,2014 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#ifndef BOTAN_GFP_CURVE_H_

#define BOTAN_GFP_CURVE_H_

#include <botan/bigint.h>

#include <memory>

// Currently exposed in EC_Point

//BOTAN_FUTURE_INTERNAL_HEADER(curve_gfp.h)

namespace Botan {

class BOTAN_UNSTABLE_API CurveGFp_Repr {

   public:

      virtual ~CurveGFp_Repr() = default;

      friend class CurveGFp;

   protected:

      virtual const BigInt& get_p() const = 0;

      virtual const BigInt& get_a() const = 0;

      virtual const BigInt& get_b() const = 0;

      size_t get_p_words() const {

         const size_t W_bits = sizeof(word) * 8;

         return (get_p_bits() + W_bits - 1) / W_bits;

      }

      virtual size_t get_p_bits() const = 0;

      virtual size_t get_ws_size() const = 0;

      virtual bool is_one(const BigInt& x) const = 0;

      virtual bool a_is_zero() const = 0;

      virtual bool a_is_minus_3() const = 0;

      /*

      * Returns to_curve_rep(get_a())

      */

      virtual const BigInt& get_a_rep() const = 0;

      /*

      * Returns to_curve_rep(get_b())

      */

      virtual const BigInt& get_b_rep() const = 0;

      /*

      * Returns to_curve_rep(1)

      */

      virtual const BigInt& get_1_rep() const = 0;

      virtual BigInt invert_element(const BigInt& x, secure_vector<word>& ws) const = 0;

      virtual void to_curve_rep(BigInt& x, secure_vector<word>& ws) const = 0;

      virtual void from_curve_rep(BigInt& x, secure_vector<word>& ws) const = 0;

      void curve_mul(BigInt& z, const BigInt& x, const BigInt& y, secure_vector<word>& ws) const {

         BOTAN_DEBUG_ASSERT(x.sig_words() <= get_p_words());

         curve_mul_words(z, x._data(), x.size(), y, ws);

      }

      virtual void curve_mul_words(

         BigInt& z, const word x_words[], size_t x_size, const BigInt& y, secure_vector<word>& ws) const = 0;

      void curve_sqr(BigInt& z, const BigInt& x, secure_vector<word>& ws) const {

         BOTAN_DEBUG_ASSERT(x.sig_words() <= get_p_words());

         curve_sqr_words(z, x._data(), x.size(), ws);

      }

      virtual void curve_sqr_words(BigInt& z, const word x_words[], size_t x_size, secure_vector<word>& ws) const = 0;

};

/**

* This class represents an elliptic curve over GF(p)

*

* There should not be any reason for applications to use this type.

* If you need EC primitives use the interfaces EC_Group and EC_Point

*

* It is likely this class will be removed entirely in a future major

* release.

*/

class BOTAN_UNSTABLE_API CurveGFp final {

   public:

      /**

      * @return curve coefficient a

      */

      const BigInt& get_a() const { return m_repr->get_a(); }

      /**

      * @return curve coefficient b

      */

      const BigInt& get_b() const { return m_repr->get_b(); }

      /**

      * Get prime modulus of the field of the curve

      * @return prime modulus of the field of the curve

      */

      const BigInt& get_p() const { return m_repr->get_p(); }

   private:

      friend class EC_Point;

      friend class EC_Group;

      friend class EC_Group_Data;

      friend class EC_Point_Base_Point_Precompute;

      friend class EC_Point_Var_Point_Precompute;

      /**

      * Create an uninitialized CurveGFp

      */

      CurveGFp() = default;

      /**

      * Construct the elliptic curve E: y^2 = x^3 + ax + b over GF(p)

      * @param p prime number of the field

      * @param a first coefficient

      * @param b second coefficient

      */

      CurveGFp(const BigInt& p, const BigInt& a, const BigInt& b) : m_repr(choose_repr(p, a, b)) {}

      CurveGFp(const CurveGFp&) = default;

      CurveGFp& operator=(const CurveGFp&) = default;

      size_t get_p_words() const { return m_repr->get_p_words(); }

      size_t get_p_bits() const { return m_repr->get_p_bits(); }

      size_t get_p_bytes() const { return (get_p_bits() + 7) / 8; }

      size_t get_ws_size() const { return m_repr->get_ws_size(); }

      const BigInt& get_a_rep() const { return m_repr->get_a_rep(); }

      const BigInt& get_b_rep() const { return m_repr->get_b_rep(); }

      const BigInt& get_1_rep() const { return m_repr->get_1_rep(); }

      bool a_is_minus_3() const { return m_repr->a_is_minus_3(); }

      bool a_is_zero() const { return m_repr->a_is_zero(); }

      bool is_one(const BigInt& x) const { return m_repr->is_one(x); }

      BigInt invert_element(const BigInt& x, secure_vector<word>& ws) const { return m_repr->invert_element(x, ws); }

      void to_rep(BigInt& x, secure_vector<word>& ws) const { m_repr->to_curve_rep(x, ws); }

      void from_rep(BigInt& x, secure_vector<word>& ws) const { m_repr->from_curve_rep(x, ws); }

      BigInt from_rep_to_tmp(const BigInt& x, secure_vector<word>& ws) const {

         BigInt xt(x);

         m_repr->from_curve_rep(xt, ws);

         return xt;

      }

      // TODO: from_rep taking && ref

      void mul(BigInt& z, const BigInt& x, const BigInt& y, secure_vector<word>& ws) const {

         m_repr->curve_mul(z, x, y, ws);

      }

      void mul(BigInt& z, const word x_w[], size_t x_size, const BigInt& y, secure_vector<word>& ws) const {

         m_repr->curve_mul_words(z, x_w, x_size, y, ws);

      }

      void sqr(BigInt& z, const BigInt& x, secure_vector<word>& ws) const { m_repr->curve_sqr(z, x, ws); }

      void sqr(BigInt& z, const word x_w[], size_t x_size, secure_vector<word>& ws) const {

         m_repr->curve_sqr_words(z, x_w, x_size, ws);

      }

      BigInt mul(const BigInt& x, const BigInt& y, secure_vector<word>& ws) const { return mul_to_tmp(x, y, ws); }

      BigInt sqr(const BigInt& x, secure_vector<word>& ws) const { return sqr_to_tmp(x, ws); }

      BigInt mul_to_tmp(const BigInt& x, const BigInt& y, secure_vector<word>& ws) const {

         BigInt z;

         m_repr->curve_mul(z, x, y, ws);

         return z;

      }

      BigInt sqr_to_tmp(const BigInt& x, secure_vector<word>& ws) const {

         BigInt z;

         m_repr->curve_sqr(z, x, ws);

         return z;

      }

      void swap(CurveGFp& other) { std::swap(m_repr, other.m_repr); }

      friend void swap(CurveGFp& x, CurveGFp& y) { x.swap(y); }

      /**

      * Equality operator

      * @param other a curve

      * @return true iff *this is the same as other

      */

      inline bool operator==(const CurveGFp& other) const {

         if(m_repr.get() == other.m_repr.get()) {

            return true;

         }

         return (get_p() == other.get_p()) && (get_a() == other.get_a()) && (get_b() == other.get_b());

      }

      inline bool operator!=(const CurveGFp& other) const = default;

   private:

      static std::shared_ptr<CurveGFp_Repr> choose_repr(const BigInt& p, const BigInt& a, const BigInt& b);

      std::shared_ptr<CurveGFp_Repr> m_repr;

};

}  // namespace Botan

#endif