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/**
* (C) Copyright Projet SECRET, INRIA, Rocquencourt
* (C) Bhaskar Biswas and Nicolas Sendrier
*
* (C) 2014 cryptosource GmbH
* (C) 2014 Falko Strenzke fstrenzke@cryptosource.de
*
* Botan is released under the Simplified BSD License (see license.txt)
*
*/
#ifndef BOTAN_POLYN_GF2M_H__
#define BOTAN_POLYN_GF2M_H__
#include <botan/secmem.h>
#include <botan/gf2m_small_m.h>
#include <memory>
#include <utility>
namespace Botan {
class RandomNumberGenerator;
struct polyn_gf2m
{
public:
/**
* create a zero polynomial:
*/
polyn_gf2m( std::shared_ptr<GF2m_Field> sp_field );
polyn_gf2m()
:m_deg(-1)
{};
polyn_gf2m(const secure_vector<byte>& encoded, std::shared_ptr<GF2m_Field> sp_field );
polyn_gf2m& operator=(const polyn_gf2m&) = default;
bool operator==(const polyn_gf2m & other) const ;
bool operator!=(const polyn_gf2m & other) const { return !(*this == other); };
polyn_gf2m(polyn_gf2m&& other)
{
this->swap(other);
};
polyn_gf2m & operator=(polyn_gf2m&& other)
{
if(this != &other)
{
this->swap(other);
}
return *this;
}
void swap(polyn_gf2m& other);
secure_vector<byte> encode() const;
/**
* create zero polynomial with reservation of space for a degree d polynomial
*/
polyn_gf2m(int d, std::shared_ptr<GF2m_Field> sp_field);
polyn_gf2m(polyn_gf2m const& other);
/**
* create zero polynomial with allocated size determined by specified degree d:
*/
/**
* random irreducible polynomial of degree t
*/
polyn_gf2m(int t, RandomNumberGenerator& rng, std::shared_ptr<GF2m_Field> sp_field);
std::shared_ptr<GF2m_Field> get_sp_field() const
{ return msp_field; };
gf2m& operator[](size_t i) { return coeff[i]; };
gf2m operator[](size_t i) const { return coeff[i]; }
gf2m get_lead_coef() const { return coeff[m_deg]; }
gf2m get_coef(u32bit i) const { return coeff[i]; }
inline void set_coef(u32bit i, gf2m v)
{
coeff[i] = v;
};
inline void add_to_coef(u32bit i, gf2m v)
{
coeff[i] = coeff[i] ^ v;
}
std::string to_string() const;
/** decode a polynomial from memory: **/
polyn_gf2m(const byte* mem, u32bit mem_len, std::shared_ptr<GF2m_Field> sp_field);
// remove one! ^v!
/**
* create a polynomial from memory area (encoded)
*/
polyn_gf2m(int degree, const unsigned char* mem, u32bit mem_byte_len, std::shared_ptr<GF2m_Field> sp_field);
void encode(u32bit min_numo_coeffs, byte* mem, u32bit mem_len) const;
int get_degree() const;
/**
* determine the degree in a timing secure manner. the timing of this function
* only depends on the number of allocated coefficients, not on the actual
* degree
*/
int calc_degree_secure() const;
void degppf(const polyn_gf2m & g, int* p_result);
static std::vector<polyn_gf2m> sqmod_init(const polyn_gf2m & g);
static std::vector<polyn_gf2m> sqrt_mod_init(const polyn_gf2m & g);
polyn_gf2m sqmod(const std::vector<polyn_gf2m> & sq, int d);
void set_to_zero();
gf2m eval(gf2m a);
static std::pair<polyn_gf2m, polyn_gf2m> eea_with_coefficients(const polyn_gf2m & p,
const polyn_gf2m & g,
int break_deg);
void patchup_deg_secure( u32bit trgt_deg, volatile gf2m patch_elem);
private:
void set_degree(int d) { m_deg = d; }
void poly_shiftmod( const polyn_gf2m & g);
void realloc(u32bit new_size);
static polyn_gf2m gcd(polyn_gf2m const& p1, polyn_gf2m const& p2);
/**
* destructive:
*/
static void remainder(polyn_gf2m & p, const polyn_gf2m & g);
static polyn_gf2m gcd_aux(polyn_gf2m& p1, polyn_gf2m& p2);
public:
int m_deg;
secure_vector<gf2m> coeff;
std::shared_ptr<GF2m_Field> msp_field;
};
gf2m random_gf2m(RandomNumberGenerator& rng);
gf2m random_code_element(unsigned code_length, RandomNumberGenerator& rng);
std::vector<polyn_gf2m> syndrome_init(polyn_gf2m const& generator, std::vector<gf2m> const& support, int n);
/**
* Find the roots of a polynomial over GF(2^m) using the method by Federenko
* et al.
*/
secure_vector<gf2m> find_roots_gf2m_decomp(const polyn_gf2m & polyn, u32bit code_length);
}
#endif
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