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Add generate_point overload for hex string scalar
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@smlu
smlu committed Nov 20, 2023
1 parent 9b0dc02 commit bb622b1
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Showing 2 changed files with 668 additions and 119 deletions.
124 changes: 91 additions & 33 deletions include/ack/ec.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -340,7 +340,7 @@ namespace ack {
};

// Forward declaration of ec_curve_fp
template<typename BigNumT, typename CurveTag>
template<typename IntT, typename CurveTag>
struct ec_curve_fp;

/**
Expand Down Expand Up @@ -960,20 +960,50 @@ namespace ack {
* @param x - scalar to multiply base point g with.
* @return PointU - point on the curve.
*/
template<typename PointU = point_type, typename IntT>
inline PointU generate_point(const IntT &x) const
template<typename PointU = point_type, typename IntT = int_type>
[[nodiscard]] inline PointU generate_point(const IntT &x) const
{
return static_cast<const CurveT&>( *this )
.template generate_point<PointU>( x );
}

/**
* Generates a point from base point g and given hex string scalar sx.
*
* @tparam PointU - point type to create.
*
* @param sx - hex string scalar to multiply base point g with.
* @return PointU - point on the curve.
*/
template<typename PointU = point_type>
[[nodiscard]] inline PointU generate_point(const std::string_view sx) const
{
return static_cast<const CurveT&>( *this )
.template generate_point<PointU>( sx );
}

/**
* Generates a point from base point g and given hex string literal scalar sx.
*
* @tparam PointU - point type to create.
*
* @param sx - hex string literal scalar to multiply base point g with.
* @return PointU - point on the curve.
*/
template<typename PointU = point_type, std::size_t N>
[[nodiscard]] inline PointU generate_point(const char (&sx)[N]) const
{
return static_cast<const CurveT&>( *this )
.template generate_point<PointU>( sx );
}

/**
* Returns curve field element from the given integer.
* @param x the integer to convert
* @return curve field element
*/
template<typename BigNumT = int_type>
[[nodiscard]] inline constexpr field_element_type make_field_element(BigNumT&& x) const
template<typename IntT = int_type>
[[nodiscard]] inline constexpr field_element_type make_field_element(IntT&& x) const
{
return static_cast<const CurveT&>( *this )
.make_field_element( std::move(x) );
Expand All @@ -984,8 +1014,8 @@ namespace ack {
* @param x the integer to convert
* @return curve field element
*/
template<typename BigNumT = int_type>
[[nodiscard]] inline constexpr field_element_type make_field_element(const BigNumT& x) const
template<typename IntT = int_type>
[[nodiscard]] inline constexpr field_element_type make_field_element(const IntT& x) const
{
return static_cast<const CurveT&>( *this )
.make_field_element( x );
Expand All @@ -998,8 +1028,8 @@ namespace ack {
* @param verify if true, the point is verified to be valid point on the curve created by the curve generator point g.
* @return curve point
*/
template<typename BigNumT = int_type>
[[nodiscard]] inline constexpr point_type make_point(BigNumT x, BigNumT y, bool verify = false) const
template<typename IntT = int_type>
[[nodiscard]] inline constexpr point_type make_point(IntT x, IntT y, bool verify = false) const
{
return static_cast<const CurveT&>( *this )
.make_point( std::move(x), std::move(y), verify );
Expand All @@ -1019,31 +1049,31 @@ namespace ack {
* Struct defines curve over a prime finite field GF(p)
* with Weierstrass equation y^2 = x^3 + ax + b.
*
* @tparam BigNumT - big number type
* @tparam IntT - integer type
* @tparam CurveTag - the curve tag
*/
template<typename BigNumT, typename CurveTag>
template<typename IntT, typename CurveTag>
struct ec_curve_fp :
ec_curve_base<
ec_curve_fp<BigNumT, CurveTag>,
fp_element<BigNumT, CurveTag>,
ec_point_fp<ec_curve_fp<BigNumT, CurveTag>>
ec_curve_fp<IntT, CurveTag>,
fp_element<IntT, CurveTag>,
ec_point_fp<ec_curve_fp<IntT, CurveTag>>
>
{
using base_type = ec_curve_base<ec_curve_fp<BigNumT, CurveTag>,
fp_element<BigNumT, CurveTag>,
ec_point_fp<ec_curve_fp<BigNumT, CurveTag>>>;
using base_type = ec_curve_base<ec_curve_fp<IntT, CurveTag>,
fp_element<IntT, CurveTag>,
ec_point_fp<ec_curve_fp<IntT, CurveTag>>>;

using curve_tag = CurveTag;
using int_type = BigNumT;
using int_type = IntT;
using field_element_type = typename base_type::field_element_type;
using point_type = typename base_type::point_type;

const BigNumT p; // curve prime
const BigNumT a; // curve coefficient
const BigNumT b; // curve coefficient
const IntT p; // curve prime
const IntT a; // curve coefficient
const IntT b; // curve coefficient
const point_type g; // generator point
const BigNumT n; // order of g
const IntT n; // order of g
const uint32_t h; // cofactor, i.e.: h = #E(Fp) / n
// #E(Fp) - number of points on the curve

Expand All @@ -1056,7 +1086,7 @@ namespace ack {
* @param n - order of g
* @param h - cofactor, i.e.: h = p / n
*/
inline constexpr ec_curve_fp(BigNumT p, BigNumT a, BigNumT b, std::pair<BigNumT, BigNumT> g, BigNumT n, uint32_t h):
inline constexpr ec_curve_fp(IntT p, IntT a, IntT b, std::pair<IntT, IntT> g, IntT n, uint32_t h):
p( std::move(p) ),
a( std::move(a) ),
b( std::move(b) ),
Expand All @@ -1073,8 +1103,8 @@ namespace ack {
* @param x - scalar to multiply base point g with.
* @return PointT - point on the curve.
*/
template<typename PointT = point_type, typename IntT = BigNumT>
PointT generate_point(const IntT &x) const
template<typename PointT = point_type, typename IntNumT = IntT>
[[nodiscard]] PointT generate_point(const IntNumT& x) const
{
check( x > 0 && x < n, "x must be in range [1, n-1]" );
if constexpr (std::is_same_v<PointT, point_type>) {
Expand All @@ -1084,6 +1114,34 @@ namespace ack {
}
}

/**
* Generates a point from base point g and given hex string scalar sx.
*
* @tparam PointU - point type to create.
*
* @param sx - hex string scalar to multiply base point g with.
* @return PointU - point on the curve.
*/
template<typename PointU = point_type>
[[nodiscard]] PointU generate_point(const std::string_view sx) const
{
return generate_point<PointU>( int_type( sx ) );
}

/**
* Generates a point from base point g and given hex string literal scalar sx.
*
* @tparam PointU - point type to create.
*
* @param sx - hex string literal scalar to multiply base point g with.
* @return PointU - point on the curve.
*/
template<typename PointU = point_type, std::size_t N>
[[nodiscard]] inline PointU generate_point(const char (&sx)[N]) const
{
return generate_point<PointU>( std::string_view( sx, N ) );
}

/**
* Creates a field element from a given integer.
* @warning Returned field element stores pointer to curve prime.
Expand All @@ -1095,7 +1153,7 @@ namespace ack {
* @return Field element
*
*/
[[nodiscard]] constexpr field_element_type make_field_element(BigNumT&& x) const
[[nodiscard]] constexpr field_element_type make_field_element(IntT&& x) const
{
return make_field_element( std::move(x), /*verify=*/ true );
}
Expand All @@ -1111,7 +1169,7 @@ namespace ack {
* @return Field element
*
*/
[[nodiscard]] inline constexpr field_element_type make_field_element(const BigNumT& x) const
[[nodiscard]] inline constexpr field_element_type make_field_element(const IntT& x) const
{
return make_field_element( x, /*verify=*/ true );
}
Expand All @@ -1130,7 +1188,7 @@ namespace ack {
* Default is false. Slow operation, can be be performed also with call to point.is_valid() function.
* @return Curve point
*/
[[nodiscard]] constexpr point_type make_point(BigNumT&& x, BigNumT&& y, bool verify = false) const
[[nodiscard]] constexpr point_type make_point(IntT&& x, IntT&& y, bool verify = false) const
{
check_integer( x, "Invalid point x coordinate" );
check_integer( y, "Invalid point y coordinate" );
Expand Down Expand Up @@ -1160,7 +1218,7 @@ namespace ack {
* Default is false. Slow operation, can be be performed also with call to point.is_valid() function.
* @return Curve point
*/
[[nodiscard]] constexpr point_type make_point(const BigNumT& x, const BigNumT& y, bool verify = false) const
[[nodiscard]] constexpr point_type make_point(const IntT& x, const IntT& y, bool verify = false) const
{
check_integer( x, "Invalid point x coordinate" );
check_integer( y, "Invalid point y coordinate" );
Expand Down Expand Up @@ -1240,25 +1298,25 @@ namespace ack {
}

private:
[[nodiscard]] inline constexpr bool is_valid_integer(const BigNumT& x) const
[[nodiscard]] inline constexpr bool is_valid_integer(const IntT& x) const
{
return !x.is_negative() && x < p;
}

inline constexpr void check_integer(const BigNumT& x, const char* error) const
inline constexpr void check_integer(const IntT& x, const char* error) const
{
check( is_valid_integer( x ), error );
}

[[nodiscard]] constexpr field_element_type make_field_element(BigNumT&& x, bool verify) const
[[nodiscard]] constexpr field_element_type make_field_element(IntT&& x, bool verify) const
{
if ( verify ) {
check_integer( x, "Invalid field element value" );
}
return field_element_type( std::move(x), p );
}

[[nodiscard]] constexpr field_element_type make_field_element(const BigNumT& x, bool verify) const
[[nodiscard]] constexpr field_element_type make_field_element(const IntT& x, bool verify) const
{
if ( verify ) {
check_integer( x, "Invalid field element value" );
Expand Down
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