/*
* Copyright 2017-2019 The OpenSSL Project Authors. All Rights Reserved.
* Copyright 2015-2016 Cryptography Research, Inc.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*
* Originally written by Mike Hamburg
*/
#ifndef OSSL_CRYPTO_EC_CURVE448_POINT_448_H
# define OSSL_CRYPTO_EC_CURVE448_POINT_448_H
# include "curve448utils.h"
# include "field.h"
/* Comb config: number of combs, n, t, s. */
#define COMBS_N 5
#define COMBS_T 5
#define COMBS_S 18
/* Projective Niels coordinates */
typedef struct {
gf a, b, c;
} niels_s, niels_t[1];
typedef struct {
niels_t n;
gf z;
} pniels_t[1];
/* Precomputed base */
struct curve448_precomputed_s {
niels_t table[COMBS_N << (COMBS_T - 1)];
};
# define C448_SCALAR_LIMBS ((446-1)/C448_WORD_BITS+1)
/* The number of bits in a scalar */
# define C448_SCALAR_BITS 446
/* Number of bytes in a serialized scalar. */
# define C448_SCALAR_BYTES 56
/* X448 encoding ratio. */
# define X448_ENCODE_RATIO 2
/* Number of bytes in an x448 public key */
# define X448_PUBLIC_BYTES 56
/* Number of bytes in an x448 private key */
# define X448_PRIVATE_BYTES 56
/* Twisted Edwards extended homogeneous coordinates */
typedef struct curve448_point_s {
gf x, y, z, t;
} curve448_point_t[1];
/* Precomputed table based on a point. Can be trivial implementation. */
struct curve448_precomputed_s;
/* Precomputed table based on a point. Can be trivial implementation. */
typedef struct curve448_precomputed_s curve448_precomputed_s;
/* Scalar is stored packed, because we don't need the speed. */
typedef struct curve448_scalar_s {
c448_word_t limb[C448_SCALAR_LIMBS];
} curve448_scalar_t[1];
/* A scalar equal to 1. */
extern const curve448_scalar_t curve448_scalar_one;
/* A scalar equal to 0. */
extern const curve448_scalar_t curve448_scalar_zero;
/* The identity point on the curve. */
extern const curve448_point_t curve448_point_identity;
/* Precomputed table for the base point on the curve. */
extern const struct curve448_precomputed_s *curve448_precomputed_base;
extern const niels_t *curve448_wnaf_base;
/*
* Read a scalar from wire format or from bytes.
*
* ser (in): Serialized form of a scalar.
* out (out): Deserialized form.
*
* Returns:
* C448_SUCCESS: The scalar was correctly encoded.
* C448_FAILURE: The scalar was greater than the modulus, and has been reduced
* modulo that modulus.
*/
c448_error_t curve448_scalar_decode(curve448_scalar_t out,
const unsigned char ser[C448_SCALAR_BYTES]);
/*
* Read a scalar from wire format or from bytes. Reduces mod scalar prime.
*
* ser (in): Serialized form of a scalar.
* ser_len (in): Length of serialized form.
* out (out): Deserialized form.
*/
void curve448_scalar_decode_long(curve448_scalar_t out,
const unsigned char *ser, size_t ser_len);
/*
* Serialize a scalar to wire format.
*
* ser (out): Serialized form of a scalar.
* s (in): Deserialized scalar.
*/
void curve448_scalar_encode(unsigned char ser[C448_SCALAR_BYTES],
const curve448_scalar_t s);
/*
* Add two scalars. |a|, |b| and |out| may alias each other.
*
* a (in): One scalar.
* b (in): Another scalar.
* out (out): a+b.
*/
void curve448_scalar_add(curve448_scalar_t out,
const curve448_scalar_t a, const curve448_scalar_t b);
/*
* Subtract two scalars. |a|, |b| and |out| may alias each other.
* a (in): One scalar.
* b (in): Another scalar.
* out (out): a-b.
*/
void curve448_scalar_sub(curve448_scalar_t out,
const curve448_scalar_t a, const curve448_scalar_t b);
/*
* Multiply two scalars. |a|, |b| and |out| may alias each other.
*
* a (in): One scalar.
* b (in): Another scalar.
* out (out): a*b.
*/
void curve448_scalar_mul(curve448_scalar_t out,
const curve448_scalar_t a, const curve448_scalar_t b);
/*
* Halve a scalar. |a| and |out| may alias each other.
*
* a (in): A scalar.
* out (out): a/2.
*/
void curve448_scalar_halve(curve448_scalar_t out, const curve448_scalar_t a);
/*
* Copy a scalar. The scalars may alias each other, in which case this
* function does nothing.
*
* a (in): A scalar.
* out (out): Will become a copy of a.
*/
static ossl_inline void curve448_scalar_copy(curve448_scalar_t out,
const curve448_scalar_t a)
{
*out = *a;
}
/*
* Copy a point. The input and output may alias, in which case this function
* does nothing.
*
* a (out): A copy of the point.
* b (in): Any point.
*/
static ossl_inline void curve448_point_copy(curve448_point_t a,
const curve448_point_t b)
{
*a = *b;
}
/*
* Test whether two points are equal. If yes, return C448_TRUE, else return
* C448_FALSE.
*
* a (in): A point.
* b (in): Another point.
*
* Returns:
* C448_TRUE: The points are equal.
* C448_FALSE: The points are not equal.
*/
__owur c448_bool_t curve448_point_eq(const curve448_point_t a,
const curve448_point_t b);
/*
* Double a point. Equivalent to curve448_point_add(two_a,a,a), but potentially
* faster.
*
* two_a (out): The sum a+a.
* a (in): A point.
*/
void curve448_point_double(curve448_point_t two_a, const curve448_point_t a);
/*
* RFC 7748 Diffie-Hellman scalarmul. This function uses a different
* (non-Decaf) encoding.
*
* out (out): The scaled point base*scalar
* base (in): The point to be scaled.
* scalar (in): The scalar to multiply by.
*
* Returns:
* C448_SUCCESS: The scalarmul succeeded.
* C448_FAILURE: The scalarmul didn't succeed, because the base point is in a
* small subgroup.
*/
__owur c448_error_t x448_int(uint8_t out[X448_PUBLIC_BYTES],
const uint8_t base[X448_PUBLIC_BYTES],
const uint8_t scalar[X448_PRIVATE_BYTES]);
/*
* Multiply a point by X448_ENCODE_RATIO, then encode it like RFC 7748.
*
* This function is mainly used internally, but is exported in case
* it will be useful.
*
* The ratio is necessary because the internal representation doesn't
* track the cofactor information, so on output we must clear the cofactor.
* This would multiply by the cofactor, but in fact internally points are always
* even, so it multiplies by half the cofactor instead.
*
* As it happens, this aligns with the base point definitions; that is,
* if you pass the Decaf/Ristretto base point to this function, the result
* will be X448_ENCODE_RATIO times the X448
* base point.
*
* out (out): The scaled and encoded point.
* p (in): The point to be scaled and encoded.
*/
void curve448_point_mul_by_ratio_and_encode_like_x448(
uint8_t out[X448_PUBLIC_BYTES],
const curve448_point_t p);
/*
* RFC 7748 Diffie-Hellman base point scalarmul. This function uses a different
* (non-Decaf) encoding.
*
* out (out): The scaled point base*scalar
* scalar (in): The scalar to multiply by.
*/
void x448_derive_public_key(uint8_t out[X448_PUBLIC_BYTES],
const uint8_t scalar[X448_PRIVATE_BYTES]);
/*
* Multiply a precomputed base point by a scalar: out = scalar*base.
*
* scaled (out): The scaled point base*scalar
* base (in): The point to be scaled.
* scalar (in): The scalar to multiply by.
*/
void curve448_precomputed_scalarmul(curve448_point_t scaled,
const curve448_precomputed_s * base,
const curve448_scalar_t scalar);
/*
* Multiply two base points by two scalars:
* combo = scalar1*curve448_point_base + scalar2*base2.
*
* Otherwise equivalent to curve448_point_double_scalarmul, but may be
* faster at the expense of being variable time.
*
* combo (out): The linear combination scalar1*base + scalar2*base2.
* scalar1 (in): A first scalar to multiply by.
* base2 (in): A second point to be scaled.
* scalar2 (in) A second scalar to multiply by.
*
* Warning: This function takes variable time, and may leak the scalars used.
* It is designed for signature verification.
*/
void curve448_base_double_scalarmul_non_secret(curve448_point_t combo,
const curve448_scalar_t scalar1,
const curve448_point_t base2,
const curve448_scalar_t scalar2);
/*
* Test that a point is valid, for debugging purposes.
*
* to_test (in): The point to test.
*
* Returns:
* C448_TRUE The point is valid.
* C448_FALSE The point is invalid.
*/
__owur c448_bool_t curve448_point_valid(const curve448_point_t to_test);
/* Overwrite scalar with zeros. */
void curve448_scalar_destroy(curve448_scalar_t scalar);
/* Overwrite point with zeros. */
void curve448_point_destroy(curve448_point_t point);
#endif /* OSSL_CRYPTO_EC_CURVE448_POINT_448_H */