105 lines
4.6 KiB
C
105 lines
4.6 KiB
C
/**********************************************************************
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* Copyright (c) 2014 Pieter Wuille *
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* Distributed under the MIT software license, see the accompanying *
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* file COPYING or http://www.opensource.org/licenses/mit-license.php.*
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**********************************************************************/
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#ifndef _SECP256K1_SCALAR_
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#define _SECP256K1_SCALAR_
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#include "num.h"
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#if defined HAVE_CONFIG_H
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#include "libsecp256k1-config.h"
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#endif
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#if defined(USE_SCALAR_4X64)
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#include "scalar_4x64.h"
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#elif defined(USE_SCALAR_8X32)
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#include "scalar_8x32.h"
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#else
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#error "Please select scalar implementation"
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#endif
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/** Clear a scalar to prevent the leak of sensitive data. */
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static void secp256k1_scalar_clear(secp256k1_scalar *r);
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/** Access bits from a scalar. All requested bits must belong to the same 32-bit limb. */
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static unsigned int secp256k1_scalar_get_bits(const secp256k1_scalar *a, unsigned int offset, unsigned int count);
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/** Access bits from a scalar. Not constant time. */
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static unsigned int secp256k1_scalar_get_bits_var(const secp256k1_scalar *a, unsigned int offset, unsigned int count);
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/** Set a scalar from a big endian byte array. */
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static void secp256k1_scalar_set_b32(secp256k1_scalar *r, const unsigned char *bin, int *overflow);
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/** Set a scalar to an unsigned integer. */
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static void secp256k1_scalar_set_int(secp256k1_scalar *r, unsigned int v);
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/** Convert a scalar to a byte array. */
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static void secp256k1_scalar_get_b32(unsigned char *bin, const secp256k1_scalar* a);
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/** Add two scalars together (modulo the group order). Returns whether it overflowed. */
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static int secp256k1_scalar_add(secp256k1_scalar *r, const secp256k1_scalar *a, const secp256k1_scalar *b);
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/** Conditionally add a power of two to a scalar. The result is not allowed to overflow. */
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static void secp256k1_scalar_cadd_bit(secp256k1_scalar *r, unsigned int bit, int flag);
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/** Multiply two scalars (modulo the group order). */
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static void secp256k1_scalar_mul(secp256k1_scalar *r, const secp256k1_scalar *a, const secp256k1_scalar *b);
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/** Shift a scalar right by some amount strictly between 0 and 16, returning
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* the low bits that were shifted off */
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static int secp256k1_scalar_shr_int(secp256k1_scalar *r, int n);
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/** Compute the square of a scalar (modulo the group order). */
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static void secp256k1_scalar_sqr(secp256k1_scalar *r, const secp256k1_scalar *a);
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/** Compute the inverse of a scalar (modulo the group order). */
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static void secp256k1_scalar_inverse(secp256k1_scalar *r, const secp256k1_scalar *a);
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/** Compute the inverse of a scalar (modulo the group order), without constant-time guarantee. */
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static void secp256k1_scalar_inverse_var(secp256k1_scalar *r, const secp256k1_scalar *a);
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/** Compute the complement of a scalar (modulo the group order). */
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static void secp256k1_scalar_negate(secp256k1_scalar *r, const secp256k1_scalar *a);
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/** Check whether a scalar equals zero. */
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static int secp256k1_scalar_is_zero(const secp256k1_scalar *a);
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/** Check whether a scalar equals one. */
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static int secp256k1_scalar_is_one(const secp256k1_scalar *a);
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/** Check whether a scalar, considered as an nonnegative integer, is even. */
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static int secp256k1_scalar_is_even(const secp256k1_scalar *a);
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/** Check whether a scalar is higher than the group order divided by 2. */
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static int secp256k1_scalar_is_high(const secp256k1_scalar *a);
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/** Conditionally negate a number, in constant time.
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* Returns -1 if the number was negated, 1 otherwise */
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static int secp256k1_scalar_cond_negate(secp256k1_scalar *a, int flag);
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#ifndef USE_NUM_NONE
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/** Convert a scalar to a number. */
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static void secp256k1_scalar_get_num(secp256k1_num *r, const secp256k1_scalar *a);
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/** Get the order of the group as a number. */
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static void secp256k1_scalar_order_get_num(secp256k1_num *r);
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#endif
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/** Compare two scalars. */
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static int secp256k1_scalar_eq(const secp256k1_scalar *a, const secp256k1_scalar *b);
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#ifdef USE_ENDOMORPHISM
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/** Find r1 and r2 such that r1+r2*2^128 = a. */
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static void secp256k1_scalar_split_128(secp256k1_scalar *r1, secp256k1_scalar *r2, const secp256k1_scalar *a);
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/** Find r1 and r2 such that r1+r2*lambda = a, and r1 and r2 are maximum 128 bits long (see secp256k1_gej_mul_lambda). */
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static void secp256k1_scalar_split_lambda(secp256k1_scalar *r1, secp256k1_scalar *r2, const secp256k1_scalar *a);
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#endif
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/** 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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static void secp256k1_scalar_mul_shift_var(secp256k1_scalar *r, const secp256k1_scalar *a, const secp256k1_scalar *b, unsigned int shift);
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#endif
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