algebra/include/nil/crypto3/algebra/curves/detail/scalar_mul.hpp

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//---------------------------------------------------------------------------//
// Copyright (c) 2020-2021 Mikhail Komarov <nemo@nil.foundation>
// Copyright (c) 2020-2021 Ilias Khairullin <ilias@nil.foundation>
// Copyright (c) 2020-2021 Nikita Kaskov <nbering@nil.foundation>
//
// MIT License
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// furnished to do so, subject to the following conditions:
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// The above copyright notice and this permission notice shall be included in all
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//---------------------------------------------------------------------------//
 
#ifndef CRYPTO3_ALGEBRA_CURVES_SCALAR_MUL_HPP
#define CRYPTO3_ALGEBRA_CURVES_SCALAR_MUL_HPP
 
#include <nil/crypto3/algebra/type_traits.hpp>
 
#include <nil/crypto3/multiprecision/number.hpp>
#include <nil/crypto3/multiprecision/modular/modular_adaptor.hpp>
 
#include <cstdint>
 
namespace nil {
    namespace crypto3 {
        namespace algebra {
            namespace curves {
                namespace detail {
                    template<typename GroupValueType,
                             typename Backend,
                             multiprecision::expression_template_option ExpressionTemplates>
                    constexpr GroupValueType
                        scalar_mul(const GroupValueType &base,
                                   const multiprecision::number<Backend, ExpressionTemplates> &scalar) {
                        if (scalar.is_zero()) {
                            return GroupValueType::zero();
                        }
                        GroupValueType result;
 
                        bool found_one = false;
                        for (auto i = static_cast<std::int64_t>(multiprecision::msb(scalar)); i >= 0; --i) {
                            if (found_one) {
                                result = result.doubled();
                            }
 
                            if (multiprecision::bit_test(scalar, i)) {
                                found_one = true;
                                result = result + base;
                            }
                        }
 
                        return result;
                    }
 
                    template<typename GroupValueType,
                             typename Backend, typename SafeType,
                             multiprecision::expression_template_option ExpressionTemplates>
                    constexpr GroupValueType
                        operator*(const GroupValueType &left,
                                  const multiprecision::number<nil::crypto3::multiprecision::backends::modular_adaptor<Backend, SafeType>, ExpressionTemplates> &right) {
                        multiprecision::number<Backend, ExpressionTemplates> tmp = right.template convert_to<multiprecision::number<Backend, ExpressionTemplates>>();
                        return scalar_mul(left, right);
                    }
 
                    template<typename GroupValueType,
                             typename Backend,
                             multiprecision::expression_template_option ExpressionTemplates>
                    constexpr GroupValueType
                        operator*(const GroupValueType &left,
                                  const multiprecision::number<Backend, ExpressionTemplates> &right) {
 
                        return scalar_mul(left, right);
                    }
 
                    template<typename GroupValueType,
                             typename Backend,
                             multiprecision::expression_template_option ExpressionTemplates>
                    constexpr GroupValueType operator*(const multiprecision::number<Backend, ExpressionTemplates> &left,
                                                       const GroupValueType &right) {
 
                        return right * left;
                    }
 
                    /*template<typename GroupValueType, typename =
                        typename std::enable_if<is_curve_group<typename
                    GroupValueType::group_type>::value &&
                                                !is_field<typename
                    GroupValueType::group_type>::value>::type> GroupValueType operator*( const GroupValueType &left,
                        const typename GroupValueType::underlying_field_type::integral_type &right) {
 
                        return scalar_mul(left, right);
                    }
 
                    template<typename GroupValueType, typename =
                        typename std::enable_if<is_curve_group<typename
                    GroupValueType::group_type>::value &&
                                                !is_field<typename
                    GroupValueType::group_type>::value>::type> GroupValueType operator*( const typename
                    GroupValueType::underlying_field_type::integral_type &left, const GroupValueType &right) {
 
                        return right * left;
                    }*/
 
                    template<typename GroupValueType, typename FieldValueType>
                    typename std::enable_if<is_curve_group<typename GroupValueType::group_type>::value &&
                                                !is_field<typename GroupValueType::group_type>::value &&
                                                is_field<typename FieldValueType::field_type>::value &&
                                                !is_extended_field<typename FieldValueType::field_type>::value,
                                            GroupValueType>::type
                        operator*(const GroupValueType &left, const FieldValueType &right) {
 
                        return left * right.data;
                    }
 
                    template<typename GroupValueType, typename FieldValueType>
                    typename std::enable_if<is_curve_group<typename GroupValueType::group_type>::value &&
                                                !is_field<typename GroupValueType::group_type>::value &&
                                                is_field<typename FieldValueType::field_type>::value &&
                                                !is_extended_field<typename FieldValueType::field_type>::value,
                                            GroupValueType>::type
                        operator*(const FieldValueType &left, const GroupValueType &right) {
 
                        return right * left;
                    }
 
                    template<typename GroupValueType>
                    constexpr GroupValueType operator*(const GroupValueType &left, const std::size_t &right) {
 
                        return scalar_mul(left, typename GroupValueType::field_type::integral_type::value_type(right));
                    }
 
                    template<typename GroupValueType>
                    constexpr GroupValueType operator*(const std::size_t &left, const GroupValueType &right) {
 
                        return right * left;
                    }
                }    // namespace detail
            }        // namespace curves
        }            // namespace algebra
    }                // namespace crypto3
}    // namespace nil
#endif    // CRYPTO3_ALGEBRA_CURVES_SCALAR_MUL_HPP