scalar.h File Reference

#include "util.h"
#include "scalar_8x32.h"

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Functions
static void	secp256k1_scalar_clear (secp256k1_scalar *r)
	Clear a scalar to prevent the leak of sensitive data. More...
static unsigned int	secp256k1_scalar_get_bits (const secp256k1_scalar *a, unsigned int offset, unsigned int count)
	Access bits from a scalar. More...
static unsigned int	secp256k1_scalar_get_bits_var (const secp256k1_scalar *a, unsigned int offset, unsigned int count)
	Access bits from a scalar. More...
static void	secp256k1_scalar_set_b32 (secp256k1_scalar *r, const unsigned char *bin, int *overflow)
	Set a scalar from a big endian byte array. More...
static int	secp256k1_scalar_set_b32_seckey (secp256k1_scalar *r, const unsigned char *bin)
	Set a scalar from a big endian byte array and returns 1 if it is a valid seckey and 0 otherwise. More...
static void	secp256k1_scalar_set_int (secp256k1_scalar *r, unsigned int v)
	Set a scalar to an unsigned integer. More...
static void	secp256k1_scalar_get_b32 (unsigned char *bin, const secp256k1_scalar *a)
	Convert a scalar to a byte array. More...
static int	secp256k1_scalar_add (secp256k1_scalar *r, const secp256k1_scalar *a, const secp256k1_scalar *b)
	Add two scalars together (modulo the group order). More...
static void	secp256k1_scalar_cadd_bit (secp256k1_scalar *r, unsigned int bit, int flag)
	Conditionally add a power of two to a scalar. More...
static void	secp256k1_scalar_mul (secp256k1_scalar *r, const secp256k1_scalar *a, const secp256k1_scalar *b)
	Multiply two scalars (modulo the group order). More...
static int	secp256k1_scalar_shr_int (secp256k1_scalar *r, int n)
	Shift a scalar right by some amount strictly between 0 and 16, returning the low bits that were shifted off. More...
static void	secp256k1_scalar_inverse (secp256k1_scalar *r, const secp256k1_scalar *a)
	Compute the inverse of a scalar (modulo the group order). More...
static void	secp256k1_scalar_inverse_var (secp256k1_scalar *r, const secp256k1_scalar *a)
	Compute the inverse of a scalar (modulo the group order), without constant-time guarantee. More...
static void	secp256k1_scalar_negate (secp256k1_scalar *r, const secp256k1_scalar *a)
	Compute the complement of a scalar (modulo the group order). More...
static int	secp256k1_scalar_is_zero (const secp256k1_scalar *a)
	Check whether a scalar equals zero. More...
static int	secp256k1_scalar_is_one (const secp256k1_scalar *a)
	Check whether a scalar equals one. More...
static int	secp256k1_scalar_is_even (const secp256k1_scalar *a)
	Check whether a scalar, considered as an nonnegative integer, is even. More...
static int	secp256k1_scalar_is_high (const secp256k1_scalar *a)
	Check whether a scalar is higher than the group order divided by 2. More...
static int	secp256k1_scalar_cond_negate (secp256k1_scalar *a, int flag)
	Conditionally negate a number, in constant time. More...
static int	secp256k1_scalar_eq (const secp256k1_scalar *a, const secp256k1_scalar *b)
	Compare two scalars. More...
static void	secp256k1_scalar_split_128 (secp256k1_scalar *r1, secp256k1_scalar *r2, const secp256k1_scalar *k)
	Find r1 and r2 such that r1+r2*2^128 = k. More...
static void	secp256k1_scalar_split_lambda (secp256k1_scalar *r1, secp256k1_scalar *r2, const secp256k1_scalar *k)
	Find r1 and r2 such that r1+r2*lambda = k, where r1 and r2 or their negations are maximum 128 bits long (see secp256k1_ge_mul_lambda). More...
static void	secp256k1_scalar_mul_shift_var (secp256k1_scalar *r, const secp256k1_scalar *a, const secp256k1_scalar *b, unsigned int shift)
	Multiply a and b (without taking the modulus!), divide by 2**shift, and round to the nearest integer. More...
static void	secp256k1_scalar_cmov (secp256k1_scalar *r, const secp256k1_scalar *a, int flag)
	If flag is true, set *r equal to *a; otherwise leave it. More...

Function Documentation

secp256k1_scalar_add()

static int secp256k1_scalar_add ( secp256k1_scalar *  r, const secp256k1_scalar *  a, const secp256k1_scalar *  b  )

static

Add two scalars together (modulo the group order).

Returns whether it overflowed.

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secp256k1_scalar_cadd_bit()

static void secp256k1_scalar_cadd_bit ( secp256k1_scalar *  r, unsigned int  bit, int  flag  )

static

Conditionally add a power of two to a scalar.

The result is not allowed to overflow.

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secp256k1_scalar_clear()

static void secp256k1_scalar_clear ( secp256k1_scalar *  r )

static

Clear a scalar to prevent the leak of sensitive data.

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secp256k1_scalar_cmov()

static void secp256k1_scalar_cmov ( secp256k1_scalar *  r, const secp256k1_scalar *  a, int  flag  )

static

If flag is true, set *r equal to *a; otherwise leave it.

Constant-time. Both *r and *a must be initialized.

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secp256k1_scalar_cond_negate()

static int secp256k1_scalar_cond_negate ( secp256k1_scalar *  a, int  flag  )

static

Conditionally negate a number, in constant time.

Returns -1 if the number was negated, 1 otherwise

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secp256k1_scalar_eq()

static int secp256k1_scalar_eq ( const secp256k1_scalar *  a, const secp256k1_scalar *  b  )

static

Compare two scalars.

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secp256k1_scalar_get_b32()

static void secp256k1_scalar_get_b32 ( unsigned char *  bin, const secp256k1_scalar *  a  )

static

Convert a scalar to a byte array.

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secp256k1_scalar_get_bits()

static unsigned int secp256k1_scalar_get_bits ( const secp256k1_scalar *  a, unsigned int  offset, unsigned int  count  )

static

Access bits from a scalar.

All requested bits must belong to the same 32-bit limb.

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secp256k1_scalar_get_bits_var()

static unsigned int secp256k1_scalar_get_bits_var ( const secp256k1_scalar *  a, unsigned int  offset, unsigned int  count  )

static

Access bits from a scalar.

Not constant time.

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secp256k1_scalar_inverse()

static void secp256k1_scalar_inverse ( secp256k1_scalar *  r, const secp256k1_scalar *  a  )

static

Compute the inverse of a scalar (modulo the group order).

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secp256k1_scalar_inverse_var()

static void secp256k1_scalar_inverse_var ( secp256k1_scalar *  r, const secp256k1_scalar *  a  )

static

Compute the inverse of a scalar (modulo the group order), without constant-time guarantee.

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secp256k1_scalar_is_even()

static int secp256k1_scalar_is_even ( const secp256k1_scalar *  a )

static

Check whether a scalar, considered as an nonnegative integer, is even.

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secp256k1_scalar_is_high()

static int secp256k1_scalar_is_high ( const secp256k1_scalar *  a )

static

Check whether a scalar is higher than the group order divided by 2.

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secp256k1_scalar_is_one()

static int secp256k1_scalar_is_one ( const secp256k1_scalar *  a )

static

Check whether a scalar equals one.

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secp256k1_scalar_is_zero()

static int secp256k1_scalar_is_zero ( const secp256k1_scalar *  a )

static

Check whether a scalar equals zero.

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secp256k1_scalar_mul()

static void secp256k1_scalar_mul ( secp256k1_scalar *  r, const secp256k1_scalar *  a, const secp256k1_scalar *  b  )

static

Multiply two scalars (modulo the group order).

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secp256k1_scalar_mul_shift_var()

static void secp256k1_scalar_mul_shift_var ( secp256k1_scalar *  r, const secp256k1_scalar *  a, const secp256k1_scalar *  b, unsigned int  shift  )

static

Multiply a and b (without taking the modulus!), divide by 2**shift, and round to the nearest integer.

Shift must be at least 256.

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secp256k1_scalar_negate()

static void secp256k1_scalar_negate ( secp256k1_scalar *  r, const secp256k1_scalar *  a  )

static

Compute the complement of a scalar (modulo the group order).

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secp256k1_scalar_set_b32()

static void secp256k1_scalar_set_b32 ( secp256k1_scalar *  r, const unsigned char *  bin, int *  overflow  )

static

Set a scalar from a big endian byte array.

The scalar will be reduced modulo group order n. In: bin: pointer to a 32-byte array. Out: r: scalar to be set. overflow: non-zero if the scalar was bigger or equal to n before reduction, zero otherwise (can be NULL).

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secp256k1_scalar_set_b32_seckey()

static int secp256k1_scalar_set_b32_seckey ( secp256k1_scalar *  r, const unsigned char *  bin  )

static

Set a scalar from a big endian byte array and returns 1 if it is a valid seckey and 0 otherwise.

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secp256k1_scalar_set_int()

static void secp256k1_scalar_set_int ( secp256k1_scalar *  r, unsigned int  v  )

static

Set a scalar to an unsigned integer.

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secp256k1_scalar_shr_int()

static int secp256k1_scalar_shr_int ( secp256k1_scalar *  r, int  n  )

static

Shift a scalar right by some amount strictly between 0 and 16, returning the low bits that were shifted off.

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secp256k1_scalar_split_128()

static void secp256k1_scalar_split_128 ( secp256k1_scalar *  r1, secp256k1_scalar *  r2, const secp256k1_scalar *  k  )

static

Find r1 and r2 such that r1+r2*2^128 = k.

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secp256k1_scalar_split_lambda()

static void secp256k1_scalar_split_lambda ( secp256k1_scalar *  r1, secp256k1_scalar *  r2, const secp256k1_scalar *  k  )

static

Find r1 and r2 such that r1+r2*lambda = k, where r1 and r2 or their negations are maximum 128 bits long (see secp256k1_ge_mul_lambda).

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