Coverage Report

Created: 2020-11-21 08:34

/src/botan/build/include/botan/internal/ed25519_fe.h
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/*
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* Ed25519 field element
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* (C) 2017 Ribose Inc
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*
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* Based on the public domain code from SUPERCOP ref10 by
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* Peter Schwabe, Daniel J. Bernstein, Niels Duif, Tanja Lange, Bo-Yin Yang
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*
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* Botan is released under the Simplified BSD License (see license.txt)
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*/
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#ifndef BOTAN_ED25519_FE_H_
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#define BOTAN_ED25519_FE_H_
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#include <botan/mem_ops.h>
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#include <botan/exceptn.h>
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namespace Botan {
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/**
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* An element of the field \\Z/(2^255-19)
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*/
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class FE_25519
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   {
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   public:
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      ~FE_25519() { secure_scrub_memory(m_fe, sizeof(m_fe)); }
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      /**
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      * Zero element
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      */
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      FE_25519(int init = 0)
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         {
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         if(init != 0 && init != 1)
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            throw Invalid_Argument("Invalid FE_25519 initial value");
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         clear_mem(m_fe, 10);
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         m_fe[0] = init;
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         }
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      FE_25519(std::initializer_list<int32_t> x)
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         {
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         if(x.size() != 10)
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            throw Invalid_Argument("Invalid FE_25519 initializer list");
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         copy_mem(m_fe, x.begin(), 10);
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         }
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      FE_25519(int64_t h0, int64_t h1, int64_t h2, int64_t h3, int64_t h4,
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               int64_t h5, int64_t h6, int64_t h7, int64_t h8, int64_t h9)
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         {
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         m_fe[0] = static_cast<int32_t>(h0);
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         m_fe[1] = static_cast<int32_t>(h1);
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         m_fe[2] = static_cast<int32_t>(h2);
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         m_fe[3] = static_cast<int32_t>(h3);
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         m_fe[4] = static_cast<int32_t>(h4);
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         m_fe[5] = static_cast<int32_t>(h5);
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         m_fe[6] = static_cast<int32_t>(h6);
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         m_fe[7] = static_cast<int32_t>(h7);
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         m_fe[8] = static_cast<int32_t>(h8);
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         m_fe[9] = static_cast<int32_t>(h9);
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         }
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      FE_25519(const FE_25519& other) = default;
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      FE_25519& operator=(const FE_25519& other) = default;
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      FE_25519(FE_25519&& other) = default;
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      FE_25519& operator=(FE_25519&& other) = default;
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      void from_bytes(const uint8_t b[32]);
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      void to_bytes(uint8_t b[32]) const;
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      bool is_zero() const
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         {
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         uint8_t s[32];
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         to_bytes(s);
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         uint8_t sum = 0;
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         for(size_t i = 0; i != 32; ++i)
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            { sum |= s[i]; }
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         // TODO avoid ternary here
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         return (sum == 0) ? 1 : 0;
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         }
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      /*
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      return 1 if f is in {1,3,5,...,q-2}
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      return 0 if f is in {0,2,4,...,q-1}
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      */
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      bool is_negative() const
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         {
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         // TODO could avoid most of the to_bytes computation here
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         uint8_t s[32];
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         to_bytes(s);
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         return s[0] & 1;
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         }
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      static FE_25519 add(const FE_25519& a, const FE_25519& b)
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         {
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         FE_25519 z;
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         for(size_t i = 0; i != 10; ++i)
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            { z[i] = a[i] + b[i]; }
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         return z;
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         }
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      static FE_25519 sub(const FE_25519& a, const FE_25519& b)
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         {
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         FE_25519 z;
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         for(size_t i = 0; i != 10; ++i)
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            { z[i] = a[i] - b[i]; }
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         return z;
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         }
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      static FE_25519 negate(const FE_25519& a)
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         {
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         FE_25519 z;
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         for(size_t i = 0; i != 10; ++i)
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            { z[i] = -a[i]; }
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         return z;
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         }
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      static FE_25519 mul(const FE_25519& a, const FE_25519& b);
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      static FE_25519 sqr_iter(const FE_25519& a, size_t iter);
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      static FE_25519 sqr(const FE_25519& a) { return sqr_iter(a, 1); }
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      static FE_25519 sqr2(const FE_25519& a);
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      static FE_25519 pow_22523(const FE_25519& a);
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      static FE_25519 invert(const FE_25519& a);
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      // TODO remove
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      int32_t operator[](size_t i) const { return m_fe[i]; }
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      int32_t& operator[](size_t i) { return m_fe[i]; }
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   private:
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      int32_t m_fe[10];
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   };
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typedef FE_25519 fe;
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/*
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fe means field element.
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Here the field is
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An element t, entries t[0]...t[9], represents the integer
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t[0]+2^26 t[1]+2^51 t[2]+2^77 t[3]+2^102 t[4]+...+2^230 t[9].
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Bounds on each t[i] vary depending on context.
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*/
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inline void fe_frombytes(fe& x, const uint8_t* b)
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   {
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   x.from_bytes(b);
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   }
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inline void fe_tobytes(uint8_t* b, const fe& x)
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   {
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   x.to_bytes(b);
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   }
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inline void fe_copy(fe& a, const fe& b)
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   {
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   a = b;
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   }
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inline int fe_isnonzero(const fe& x)
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   {
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   return x.is_zero() ? 0 : 1;
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   }
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inline int fe_isnegative(const fe& x)
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   {
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   return x.is_negative();
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   }
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inline void fe_0(fe& x)
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   {
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   x = FE_25519();
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   }
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inline void fe_1(fe& x)
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   {
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   x = FE_25519(1);
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   }
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inline void fe_add(fe& x, const fe& a, const fe& b)
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   {
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   x = FE_25519::add(a, b);
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   }
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inline void fe_sub(fe& x, const fe& a, const fe& b)
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   {
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   x = FE_25519::sub(a, b);
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   }
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inline void fe_neg(fe& x, const fe& z)
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   {
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   x = FE_25519::negate(z);
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   }
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inline void fe_mul(fe& x, const fe& a, const fe& b)
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   {
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   x = FE_25519::mul(a, b);
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   }
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inline void fe_sq(fe& x, const fe& z)
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   {
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   x = FE_25519::sqr(z);
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   }
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inline void fe_sq_iter(fe& x, const fe& z, size_t iter)
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   {
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   x = FE_25519::sqr_iter(z, iter);
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   }
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inline void fe_sq2(fe& x, const fe& z)
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   {
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   x = FE_25519::sqr2(z);
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   }
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inline void fe_invert(fe& x, const fe& z)
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   {
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   x = FE_25519::invert(z);
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   }
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inline void fe_pow22523(fe& x, const fe& y)
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   {
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   x = FE_25519::pow_22523(y);
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   }
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}
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#endif