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Diffstat (limited to 'src/secp256k1/src/field.h')
-rw-r--r-- | src/secp256k1/src/field.h | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/src/secp256k1/src/field.h b/src/secp256k1/src/field.h new file mode 100644 index 0000000000..c7feead900 --- /dev/null +++ b/src/secp256k1/src/field.h @@ -0,0 +1,114 @@ +/********************************************************************** + * Copyright (c) 2013, 2014 Pieter Wuille * + * Distributed under the MIT software license, see the accompanying * + * file COPYING or http://www.opensource.org/licenses/mit-license.php.* + **********************************************************************/ + +#ifndef _SECP256K1_FIELD_ +#define _SECP256K1_FIELD_ + +/** Field element module. + * + * Field elements can be represented in several ways, but code accessing + * it (and implementations) need to take certain properaties into account: + * - Each field element can be normalized or not. + * - Each field element has a magnitude, which represents how far away + * its representation is away from normalization. Normalized elements + * always have a magnitude of 1, but a magnitude of 1 doesn't imply + * normality. + */ + +#if defined HAVE_CONFIG_H +#include "libsecp256k1-config.h" +#endif + +#if defined(USE_FIELD_GMP) +#include "field_gmp.h" +#elif defined(USE_FIELD_10X26) +#include "field_10x26.h" +#elif defined(USE_FIELD_5X52) +#include "field_5x52.h" +#else +#error "Please select field implementation" +#endif + +typedef struct { + secp256k1_num_t p; +} secp256k1_fe_consts_t; + +static const secp256k1_fe_consts_t *secp256k1_fe_consts = NULL; + +/** Initialize field element precomputation data. */ +static void secp256k1_fe_start(void); + +/** Unload field element precomputation data. */ +static void secp256k1_fe_stop(void); + +/** Normalize a field element. */ +static void secp256k1_fe_normalize(secp256k1_fe_t *r); + +/** Set a field element equal to a small integer. Resulting field element is normalized. */ +static void secp256k1_fe_set_int(secp256k1_fe_t *r, int a); + +/** Verify whether a field element is zero. Requires the input to be normalized. */ +static int secp256k1_fe_is_zero(const secp256k1_fe_t *a); + +/** Check the "oddness" of a field element. Requires the input to be normalized. */ +static int secp256k1_fe_is_odd(const secp256k1_fe_t *a); + +/** Compare two field elements. Requires both inputs to be normalized */ +static int secp256k1_fe_equal(const secp256k1_fe_t *a, const secp256k1_fe_t *b); + +/** Set a field element equal to 32-byte big endian value. Resulting field element is normalized. */ +static void secp256k1_fe_set_b32(secp256k1_fe_t *r, const unsigned char *a); + +/** Convert a field element to a 32-byte big endian value. Requires the input to be normalized */ +static void secp256k1_fe_get_b32(unsigned char *r, const secp256k1_fe_t *a); + +/** Set a field element equal to the additive inverse of another. Takes a maximum magnitude of the input + * as an argument. The magnitude of the output is one higher. */ +static void secp256k1_fe_negate(secp256k1_fe_t *r, const secp256k1_fe_t *a, int m); + +/** Multiplies the passed field element with a small integer constant. Multiplies the magnitude by that + * small integer. */ +static void secp256k1_fe_mul_int(secp256k1_fe_t *r, int a); + +/** Adds a field element to another. The result has the sum of the inputs' magnitudes as magnitude. */ +static void secp256k1_fe_add(secp256k1_fe_t *r, const secp256k1_fe_t *a); + +/** Sets a field element to be the product of two others. Requires the inputs' magnitudes to be at most 8. + * The output magnitude is 1 (but not guaranteed to be normalized). */ +static void secp256k1_fe_mul(secp256k1_fe_t *r, const secp256k1_fe_t *a, const secp256k1_fe_t *b); + +/** Sets a field element to be the square of another. Requires the input's magnitude to be at most 8. + * The output magnitude is 1 (but not guaranteed to be normalized). */ +static void secp256k1_fe_sqr(secp256k1_fe_t *r, const secp256k1_fe_t *a); + +/** Sets a field element to be the (modular) square root (if any exist) of another. Requires the + * input's magnitude to be at most 8. The output magnitude is 1 (but not guaranteed to be + * normalized). Return value indicates whether a square root was found. */ +static int secp256k1_fe_sqrt(secp256k1_fe_t *r, const secp256k1_fe_t *a); + +/** Sets a field element to be the (modular) inverse of another. Requires the input's magnitude to be + * at most 8. The output magnitude is 1 (but not guaranteed to be normalized). */ +static void secp256k1_fe_inv(secp256k1_fe_t *r, const secp256k1_fe_t *a); + +/** Potentially faster version of secp256k1_fe_inv, without constant-time guarantee. */ +static void secp256k1_fe_inv_var(secp256k1_fe_t *r, const secp256k1_fe_t *a); + +/** Calculate the (modular) inverses of a batch of field elements. Requires the inputs' magnitudes to be + * at most 8. The output magnitudes are 1 (but not guaranteed to be normalized). The inputs and + * outputs must not overlap in memory. */ +static void secp256k1_fe_inv_all(size_t len, secp256k1_fe_t r[len], const secp256k1_fe_t a[len]); + +/** Potentially faster version of secp256k1_fe_inv_all, without constant-time guarantee. */ +static void secp256k1_fe_inv_all_var(size_t len, secp256k1_fe_t r[len], const secp256k1_fe_t a[len]); + + +/** Convert a field element to a hexadecimal string. */ +static void secp256k1_fe_get_hex(char *r, int *rlen, const secp256k1_fe_t *a); + +/** Convert a hexadecimal string to a field element. */ +static void secp256k1_fe_set_hex(secp256k1_fe_t *r, const char *a, int alen); + +#endif |