106 lines
6.0 KiB
C
106 lines
6.0 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 https://www.opensource.org/licenses/mit-license.php.*
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***********************************************************************/
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#ifndef SECP256K1_SCALAR_H
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#define SECP256K1_SCALAR_H
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#include "util.h"
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#if defined(EXHAUSTIVE_TEST_ORDER)
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#include "scalar_low.h"
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#elif defined(SECP256K1_WIDEMUL_INT128)
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#include "scalar_4x64.h"
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#elif defined(SECP256K1_WIDEMUL_INT64)
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#include "scalar_8x32.h"
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#else
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#error "Please select wide multiplication 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 rustsecp256k1_v0_10_0_scalar_clear(rustsecp256k1_v0_10_0_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 rustsecp256k1_v0_10_0_scalar_get_bits(const rustsecp256k1_v0_10_0_scalar *a, unsigned int offset, unsigned int count);
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/** Access bits from a scalar. Not constant time in offset and count. */
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static unsigned int rustsecp256k1_v0_10_0_scalar_get_bits_var(const rustsecp256k1_v0_10_0_scalar *a, unsigned int offset, unsigned int count);
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/** Set a scalar from a big endian byte array. The scalar will be reduced modulo group order `n`.
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* In: bin: pointer to a 32-byte array.
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* Out: r: scalar to be set.
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* overflow: non-zero if the scalar was bigger or equal to `n` before reduction, zero otherwise (can be NULL).
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*/
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static void rustsecp256k1_v0_10_0_scalar_set_b32(rustsecp256k1_v0_10_0_scalar *r, const unsigned char *bin, int *overflow);
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/** Set a scalar from a big endian byte array and returns 1 if it is a valid
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* seckey and 0 otherwise. */
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static int rustsecp256k1_v0_10_0_scalar_set_b32_seckey(rustsecp256k1_v0_10_0_scalar *r, const unsigned char *bin);
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/** Set a scalar to an unsigned integer. */
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static void rustsecp256k1_v0_10_0_scalar_set_int(rustsecp256k1_v0_10_0_scalar *r, unsigned int v);
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/** Convert a scalar to a byte array. */
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static void rustsecp256k1_v0_10_0_scalar_get_b32(unsigned char *bin, const rustsecp256k1_v0_10_0_scalar* a);
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/** Add two scalars together (modulo the group order). Returns whether it overflowed. */
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static int rustsecp256k1_v0_10_0_scalar_add(rustsecp256k1_v0_10_0_scalar *r, const rustsecp256k1_v0_10_0_scalar *a, const rustsecp256k1_v0_10_0_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 rustsecp256k1_v0_10_0_scalar_cadd_bit(rustsecp256k1_v0_10_0_scalar *r, unsigned int bit, int flag);
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/** Multiply two scalars (modulo the group order). */
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static void rustsecp256k1_v0_10_0_scalar_mul(rustsecp256k1_v0_10_0_scalar *r, const rustsecp256k1_v0_10_0_scalar *a, const rustsecp256k1_v0_10_0_scalar *b);
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/** Compute the inverse of a scalar (modulo the group order). */
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static void rustsecp256k1_v0_10_0_scalar_inverse(rustsecp256k1_v0_10_0_scalar *r, const rustsecp256k1_v0_10_0_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 rustsecp256k1_v0_10_0_scalar_inverse_var(rustsecp256k1_v0_10_0_scalar *r, const rustsecp256k1_v0_10_0_scalar *a);
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/** Compute the complement of a scalar (modulo the group order). */
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static void rustsecp256k1_v0_10_0_scalar_negate(rustsecp256k1_v0_10_0_scalar *r, const rustsecp256k1_v0_10_0_scalar *a);
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/** Multiply a scalar with the multiplicative inverse of 2. */
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static void rustsecp256k1_v0_10_0_scalar_half(rustsecp256k1_v0_10_0_scalar *r, const rustsecp256k1_v0_10_0_scalar *a);
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/** Check whether a scalar equals zero. */
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static int rustsecp256k1_v0_10_0_scalar_is_zero(const rustsecp256k1_v0_10_0_scalar *a);
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/** Check whether a scalar equals one. */
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static int rustsecp256k1_v0_10_0_scalar_is_one(const rustsecp256k1_v0_10_0_scalar *a);
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/** Check whether a scalar, considered as an nonnegative integer, is even. */
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static int rustsecp256k1_v0_10_0_scalar_is_even(const rustsecp256k1_v0_10_0_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 rustsecp256k1_v0_10_0_scalar_is_high(const rustsecp256k1_v0_10_0_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 rustsecp256k1_v0_10_0_scalar_cond_negate(rustsecp256k1_v0_10_0_scalar *a, int flag);
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/** Compare two scalars. */
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static int rustsecp256k1_v0_10_0_scalar_eq(const rustsecp256k1_v0_10_0_scalar *a, const rustsecp256k1_v0_10_0_scalar *b);
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/** Find r1 and r2 such that r1+r2*2^128 = k. */
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static void rustsecp256k1_v0_10_0_scalar_split_128(rustsecp256k1_v0_10_0_scalar *r1, rustsecp256k1_v0_10_0_scalar *r2, const rustsecp256k1_v0_10_0_scalar *k);
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/** Find r1 and r2 such that r1+r2*lambda = k, where r1 and r2 or their
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* negations are maximum 128 bits long (see rustsecp256k1_v0_10_0_ge_mul_lambda). It is
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* required that r1, r2, and k all point to different objects. */
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static void rustsecp256k1_v0_10_0_scalar_split_lambda(rustsecp256k1_v0_10_0_scalar * SECP256K1_RESTRICT r1, rustsecp256k1_v0_10_0_scalar * SECP256K1_RESTRICT r2, const rustsecp256k1_v0_10_0_scalar * SECP256K1_RESTRICT k);
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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 rustsecp256k1_v0_10_0_scalar_mul_shift_var(rustsecp256k1_v0_10_0_scalar *r, const rustsecp256k1_v0_10_0_scalar *a, const rustsecp256k1_v0_10_0_scalar *b, unsigned int shift);
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/** 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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static void rustsecp256k1_v0_10_0_scalar_cmov(rustsecp256k1_v0_10_0_scalar *r, const rustsecp256k1_v0_10_0_scalar *a, int flag);
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/** Check invariants on a scalar (no-op unless VERIFY is enabled). */
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static void rustsecp256k1_v0_10_0_scalar_verify(const rustsecp256k1_v0_10_0_scalar *r);
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#define SECP256K1_SCALAR_VERIFY(r) rustsecp256k1_v0_10_0_scalar_verify(r)
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#endif /* SECP256K1_SCALAR_H */
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