-/**
- * @file decaf/point_255.h
- * @author Mike Hamburg
- *
- * @copyright
- * Copyright (c) 2015-2016 Cryptography Research, Inc. \n
- * Released under the MIT License. See LICENSE.txt for license information.
- *
- * @brief A group of prime order p, based on Curve25519.
- *
- * @warning This file was automatically generated in Python.
- * Please do not edit it.
- */
-
-#ifndef __DECAF_POINT_255_H__
-#define __DECAF_POINT_255_H__ 1
-
-#include <decaf/common.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-/** @cond internal */
-#define DECAF_255_SCALAR_LIMBS ((253-1)/DECAF_WORD_BITS+1)
-/** @endcond */
-
-/** The number of bits in a scalar */
-#define DECAF_255_SCALAR_BITS 253
-
-/** @cond internal */
-#ifndef __DECAF_25519_GF_DEFINED__
-#define __DECAF_25519_GF_DEFINED__ 1
-/** @brief Galois field element internal structure */
-typedef struct gf_25519_s {
- decaf_word_t limb[320/DECAF_WORD_BITS];
-} __attribute__((aligned(32))) gf_25519_s, gf_25519_t[1];
-#endif /* __DECAF_25519_GF_DEFINED__ */
-/** @endcond */
-
-/** Number of bytes in a serialized point. */
-#define DECAF_255_SER_BYTES 32
-
-/** Number of bytes in an elligated point. For now set the same as SER_BYTES
- * but could be different for other curves.
- */
-#define DECAF_255_HASH_BYTES 32
-
-/** Number of bytes in a serialized scalar. */
-#define DECAF_255_SCALAR_BYTES 32
-
-/** Number of bits in the "which" field of an elligator inverse */
-#define DECAF_255_INVERT_ELLIGATOR_WHICH_BITS 5
-
-/** The cofactor the curve would have, if we hadn't removed it */
-#define DECAF_255_REMOVED_COFACTOR 8
-
-/** X25519 encoding ratio. */
-#define DECAF_X25519_ENCODE_RATIO 4
-
-/** Number of bytes in an x25519 public key */
-#define DECAF_X25519_PUBLIC_BYTES 32
-
-/** Number of bytes in an x25519 private key */
-#define DECAF_X25519_PRIVATE_BYTES 32
-
-/** Twisted Edwards extended homogeneous coordinates */
-typedef struct decaf_255_point_s {
- /** @cond internal */
- gf_25519_t x,y,z,t;
- /** @endcond */
-} decaf_255_point_t[1];
-
-/** Precomputed table based on a point. Can be trivial implementation. */
-struct decaf_255_precomputed_s;
-
-/** Precomputed table based on a point. Can be trivial implementation. */
-typedef struct decaf_255_precomputed_s decaf_255_precomputed_s;
-
-/** Size and alignment of precomputed point tables. */
-extern const size_t decaf_255_sizeof_precomputed_s DECAF_API_VIS, decaf_255_alignof_precomputed_s DECAF_API_VIS;
-
-/** Scalar is stored packed, because we don't need the speed. */
-typedef struct decaf_255_scalar_s {
- /** @cond internal */
- decaf_word_t limb[DECAF_255_SCALAR_LIMBS];
- /** @endcond */
-} decaf_255_scalar_t[1];
-
-/** A scalar equal to 1. */
-extern const decaf_255_scalar_t decaf_255_scalar_one DECAF_API_VIS;
-
-/** A scalar equal to 0. */
-extern const decaf_255_scalar_t decaf_255_scalar_zero DECAF_API_VIS;
-
-/** The identity point on the curve. */
-extern const decaf_255_point_t decaf_255_point_identity DECAF_API_VIS;
-
-/** An arbitrarily chosen base point on the curve. */
-extern const decaf_255_point_t decaf_255_point_base DECAF_API_VIS;
-
-/** Precomputed table for the base point on the curve. */
-extern const struct decaf_255_precomputed_s *decaf_255_precomputed_base DECAF_API_VIS;
-
-/**
- * @brief Read a scalar from wire format or from bytes.
- *
- * @param [in] ser Serialized form of a scalar.
- * @param [out] out Deserialized form.
- *
- * @retval DECAF_SUCCESS The scalar was correctly encoded.
- * @retval DECAF_FAILURE The scalar was greater than the modulus,
- * and has been reduced modulo that modulus.
- */
-decaf_error_t decaf_255_scalar_decode (
- decaf_255_scalar_t out,
- const unsigned char ser[DECAF_255_SCALAR_BYTES]
-) DECAF_API_VIS DECAF_WARN_UNUSED DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Read a scalar from wire format or from bytes. Reduces mod
- * scalar prime.
- *
- * @param [in] ser Serialized form of a scalar.
- * @param [in] ser_len Length of serialized form.
- * @param [out] out Deserialized form.
- */
-void decaf_255_scalar_decode_long (
- decaf_255_scalar_t out,
- const unsigned char *ser,
- size_t ser_len
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Serialize a scalar to wire format.
- *
- * @param [out] ser Serialized form of a scalar.
- * @param [in] s Deserialized scalar.
- */
-void decaf_255_scalar_encode (
- unsigned char ser[DECAF_255_SCALAR_BYTES],
- const decaf_255_scalar_t s
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE DECAF_NOINLINE;
-
-/**
- * @brief Add two scalars. The scalars may use the same memory.
- * @param [in] a One scalar.
- * @param [in] b Another scalar.
- * @param [out] out a+b.
- */
-void decaf_255_scalar_add (
- decaf_255_scalar_t out,
- const decaf_255_scalar_t a,
- const decaf_255_scalar_t b
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Compare two scalars.
- * @param [in] a One scalar.
- * @param [in] b Another scalar.
- * @retval DECAF_TRUE The scalars are equal.
- * @retval DECAF_FALSE The scalars are not equal.
- */
-decaf_bool_t decaf_255_scalar_eq (
- const decaf_255_scalar_t a,
- const decaf_255_scalar_t b
-) DECAF_API_VIS DECAF_WARN_UNUSED DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Subtract two scalars. The scalars may use the same memory.
- * @param [in] a One scalar.
- * @param [in] b Another scalar.
- * @param [out] out a-b.
- */
-void decaf_255_scalar_sub (
- decaf_255_scalar_t out,
- const decaf_255_scalar_t a,
- const decaf_255_scalar_t b
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Multiply two scalars. The scalars may use the same memory.
- * @param [in] a One scalar.
- * @param [in] b Another scalar.
- * @param [out] out a*b.
- */
-void decaf_255_scalar_mul (
- decaf_255_scalar_t out,
- const decaf_255_scalar_t a,
- const decaf_255_scalar_t b
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
-* @brief Halve a scalar. The scalars may use the same memory.
-* @param [in] a A scalar.
-* @param [out] out a/2.
-*/
-void decaf_255_scalar_halve (
- decaf_255_scalar_t out,
- const decaf_255_scalar_t a
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Invert a scalar. When passed zero, return 0. The input and output may alias.
- * @param [in] a A scalar.
- * @param [out] out 1/a.
- * @return DECAF_SUCCESS The input is nonzero.
- */
-decaf_error_t decaf_255_scalar_invert (
- decaf_255_scalar_t out,
- const decaf_255_scalar_t a
-) DECAF_API_VIS DECAF_WARN_UNUSED DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Copy a scalar. The scalars may use the same memory, in which
- * case this function does nothing.
- * @param [in] a A scalar.
- * @param [out] out Will become a copy of a.
- */
-static inline void DECAF_NONNULL decaf_255_scalar_copy (
- decaf_255_scalar_t out,
- const decaf_255_scalar_t a
-) {
- *out = *a;
-}
-
-/**
- * @brief Set a scalar to an unsigned 64-bit integer.
- * @param [in] a An integer.
- * @param [out] out Will become equal to a.
- */
-void decaf_255_scalar_set_unsigned (
- decaf_255_scalar_t out,
- uint64_t a
-) DECAF_API_VIS DECAF_NONNULL;
-
-/**
- * @brief Encode a point as a sequence of bytes.
- *
- * @param [out] ser The byte representation of the point.
- * @param [in] pt The point to encode.
- */
-void decaf_255_point_encode (
- uint8_t ser[DECAF_255_SER_BYTES],
- const decaf_255_point_t pt
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Decode a point from a sequence of bytes.
- *
- * Every point has a unique encoding, so not every
- * sequence of bytes is a valid encoding. If an invalid
- * encoding is given, the output is undefined.
- *
- * @param [out] pt The decoded point.
- * @param [in] ser The serialized version of the point.
- * @param [in] allow_identity DECAF_TRUE if the identity is a legal input.
- * @retval DECAF_SUCCESS The decoding succeeded.
- * @retval DECAF_FAILURE The decoding didn't succeed, because
- * ser does not represent a point.
- */
-decaf_error_t decaf_255_point_decode (
- decaf_255_point_t pt,
- const uint8_t ser[DECAF_255_SER_BYTES],
- decaf_bool_t allow_identity
-) DECAF_API_VIS DECAF_WARN_UNUSED DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Copy a point. The input and output may alias,
- * in which case this function does nothing.
- *
- * @param [out] a A copy of the point.
- * @param [in] b Any point.
- */
-static inline void DECAF_NONNULL decaf_255_point_copy (
- decaf_255_point_t a,
- const decaf_255_point_t b
-) {
- *a=*b;
-}
-
-/**
- * @brief Test whether two points are equal. If yes, return
- * DECAF_TRUE, else return DECAF_FALSE.
- *
- * @param [in] a A point.
- * @param [in] b Another point.
- * @retval DECAF_TRUE The points are equal.
- * @retval DECAF_FALSE The points are not equal.
- */
-decaf_bool_t decaf_255_point_eq (
- const decaf_255_point_t a,
- const decaf_255_point_t b
-) DECAF_API_VIS DECAF_WARN_UNUSED DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Add two points to produce a third point. The
- * input points and output point can be pointers to the same
- * memory.
- *
- * @param [out] sum The sum a+b.
- * @param [in] a An addend.
- * @param [in] b An addend.
- */
-void decaf_255_point_add (
- decaf_255_point_t sum,
- const decaf_255_point_t a,
- const decaf_255_point_t b
-) DECAF_API_VIS DECAF_NONNULL;
-
-/**
- * @brief Double a point. Equivalent to
- * decaf_255_point_add(two_a,a,a), but potentially faster.
- *
- * @param [out] two_a The sum a+a.
- * @param [in] a A point.
- */
-void decaf_255_point_double (
- decaf_255_point_t two_a,
- const decaf_255_point_t a
-) DECAF_API_VIS DECAF_NONNULL;
-
-/**
- * @brief Subtract two points to produce a third point. The
- * input points and output point can be pointers to the same
- * memory.
- *
- * @param [out] diff The difference a-b.
- * @param [in] a The minuend.
- * @param [in] b The subtrahend.
- */
-void decaf_255_point_sub (
- decaf_255_point_t diff,
- const decaf_255_point_t a,
- const decaf_255_point_t b
-) DECAF_API_VIS DECAF_NONNULL;
-
-/**
- * @brief Negate a point to produce another point. The input
- * and output points can use the same memory.
- *
- * @param [out] nega The negated input point
- * @param [in] a The input point.
- */
-void decaf_255_point_negate (
- decaf_255_point_t nega,
- const decaf_255_point_t a
-) DECAF_API_VIS DECAF_NONNULL;
-
-/**
- * @brief Multiply a base point by a scalar: scaled = scalar*base.
- *
- * @param [out] scaled The scaled point base*scalar
- * @param [in] base The point to be scaled.
- * @param [in] scalar The scalar to multiply by.
- */
-void decaf_255_point_scalarmul (
- decaf_255_point_t scaled,
- const decaf_255_point_t base,
- const decaf_255_scalar_t scalar
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Multiply a base point by a scalar: scaled = scalar*base.
- * This function operates directly on serialized forms.
- *
- * @warning This function is experimental. It may not be supported
- * long-term.
- *
- * @param [out] scaled The scaled point base*scalar
- * @param [in] base The point to be scaled.
- * @param [in] scalar The scalar to multiply by.
- * @param [in] allow_identity Allow the input to be the identity.
- * @param [in] short_circuit Allow a fast return if the input is illegal.
- *
- * @retval DECAF_SUCCESS The scalarmul succeeded.
- * @retval DECAF_FAILURE The scalarmul didn't succeed, because
- * base does not represent a point.
- */
-decaf_error_t decaf_255_direct_scalarmul (
- uint8_t scaled[DECAF_255_SER_BYTES],
- const uint8_t base[DECAF_255_SER_BYTES],
- const decaf_255_scalar_t scalar,
- decaf_bool_t allow_identity,
- decaf_bool_t short_circuit
-) DECAF_API_VIS DECAF_NONNULL DECAF_WARN_UNUSED DECAF_NOINLINE;
-
-/**
- * @brief RFC 7748 Diffie-Hellman scalarmul. This function uses a different
- * (non-Decaf) encoding.
- *
- * @param [out] scaled The scaled point base*scalar
- * @param [in] base The point to be scaled.
- * @param [in] scalar The scalar to multiply by.
- *
- * @retval DECAF_SUCCESS The scalarmul succeeded.
- * @retval DECAF_FAILURE The scalarmul didn't succeed, because the base
- * point is in a small subgroup.
- */
-decaf_error_t decaf_x25519 (
- uint8_t out[DECAF_X25519_PUBLIC_BYTES],
- const uint8_t base[DECAF_X25519_PUBLIC_BYTES],
- const uint8_t scalar[DECAF_X25519_PRIVATE_BYTES]
-) DECAF_API_VIS DECAF_NONNULL DECAF_WARN_UNUSED DECAF_NOINLINE;
-
-/**
- * @brief Multiply a point by DECAF_X25519_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 libdecaf's
- * 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 DECAF_X25519_ENCODE_RATIO times the X25519
- * base point.
- *
- * @param [out] out The scaled and encoded point.
- * @param [in] p The point to be scaled and encoded.
- */
-void decaf_255_point_mul_by_ratio_and_encode_like_x25519 (
- uint8_t out[DECAF_X25519_PUBLIC_BYTES],
- const decaf_255_point_t p
-) DECAF_API_VIS DECAF_NONNULL;
-
-/** The base point for X25519 Diffie-Hellman */
-extern const uint8_t decaf_x25519_base_point[DECAF_X25519_PUBLIC_BYTES] DECAF_API_VIS;
-
-/**
- * @brief RFC 7748 Diffie-Hellman base point scalarmul. This function uses
- * a different (non-Decaf) encoding.
- *
- * @deprecated Renamed to decaf_x25519_derive_public_key.
- * I have no particular timeline for removing this name.
- *
- * @param [out] scaled The scaled point base*scalar
- * @param [in] scalar The scalar to multiply by.
- */
-void decaf_x25519_generate_key (
- uint8_t out[DECAF_X25519_PUBLIC_BYTES],
- const uint8_t scalar[DECAF_X25519_PRIVATE_BYTES]
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE DECAF_DEPRECATED("Renamed to decaf_x25519_derive_public_key");
-
-/**
- * @brief RFC 7748 Diffie-Hellman base point scalarmul. This function uses
- * a different (non-Decaf) encoding.
- *
- * Does exactly the same thing as decaf_x25519_generate_key,
- * but has a better name.
- *
- * @param [out] scaled The scaled point base*scalar
- * @param [in] scalar The scalar to multiply by.
- */
-void decaf_x25519_derive_public_key (
- uint8_t out[DECAF_X25519_PUBLIC_BYTES],
- const uint8_t scalar[DECAF_X25519_PRIVATE_BYTES]
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/* FUTURE: uint8_t decaf_255_encode_like_curve25519) */
-
-/**
- * @brief Precompute a table for fast scalar multiplication.
- * Some implementations do not include precomputed points; for
- * those implementations, this implementation simply copies the
- * point.
- *
- * @param [out] a A precomputed table of multiples of the point.
- * @param [in] b Any point.
- */
-void decaf_255_precompute (
- decaf_255_precomputed_s *a,
- const decaf_255_point_t b
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Multiply a precomputed base point by a scalar:
- * scaled = scalar*base.
- * Some implementations do not include precomputed points; for
- * those implementations, this function is the same as
- * decaf_255_point_scalarmul
- *
- * @param [out] scaled The scaled point base*scalar
- * @param [in] base The point to be scaled.
- * @param [in] scalar The scalar to multiply by.
- */
-void decaf_255_precomputed_scalarmul (
- decaf_255_point_t scaled,
- const decaf_255_precomputed_s *base,
- const decaf_255_scalar_t scalar
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Multiply two base points by two scalars:
- * scaled = scalar1*base1 + scalar2*base2.
- *
- * Equivalent to two calls to decaf_255_point_scalarmul, but may be
- * faster.
- *
- * @param [out] combo The linear combination scalar1*base1 + scalar2*base2.
- * @param [in] base1 A first point to be scaled.
- * @param [in] scalar1 A first scalar to multiply by.
- * @param [in] base2 A second point to be scaled.
- * @param [in] scalar2 A second scalar to multiply by.
- */
-void decaf_255_point_double_scalarmul (
- decaf_255_point_t combo,
- const decaf_255_point_t base1,
- const decaf_255_scalar_t scalar1,
- const decaf_255_point_t base2,
- const decaf_255_scalar_t scalar2
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * Multiply one base point by two scalars:
- *
- * a1 = scalar1 * base
- * a2 = scalar2 * base
- *
- * Equivalent to two calls to decaf_255_point_scalarmul, but may be
- * faster.
- *
- * @param [out] a1 The first multiple. It may be the same as the input point.
- * @param [out] a2 The second multiple. It may be the same as the input point.
- * @param [in] base1 A point to be scaled.
- * @param [in] scalar1 A first scalar to multiply by.
- * @param [in] scalar2 A second scalar to multiply by.
- */
-void decaf_255_point_dual_scalarmul (
- decaf_255_point_t a1,
- decaf_255_point_t a2,
- const decaf_255_point_t base1,
- const decaf_255_scalar_t scalar1,
- const decaf_255_scalar_t scalar2
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Multiply two base points by two scalars:
- * scaled = scalar1*decaf_255_point_base + scalar2*base2.
- *
- * Otherwise equivalent to decaf_255_point_double_scalarmul, but may be
- * faster at the expense of being variable time.
- *
- * @param [out] combo The linear combination scalar1*base + scalar2*base2.
- * @param [in] scalar1 A first scalar to multiply by.
- * @param [in] base2 A second point to be scaled.
- * @param [in] scalar2 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 decaf_255_base_double_scalarmul_non_secret (
- decaf_255_point_t combo,
- const decaf_255_scalar_t scalar1,
- const decaf_255_point_t base2,
- const decaf_255_scalar_t scalar2
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Constant-time decision between two points. If pick_b
- * is zero, out = a; else out = b.
- *
- * @param [out] out The output. It may be the same as either input.
- * @param [in] a Any point.
- * @param [in] b Any point.
- * @param [in] pick_b If nonzero, choose point b.
- */
-void decaf_255_point_cond_sel (
- decaf_255_point_t out,
- const decaf_255_point_t a,
- const decaf_255_point_t b,
- decaf_word_t pick_b
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Constant-time decision between two scalars. If pick_b
- * is zero, out = a; else out = b.
- *
- * @param [out] out The output. It may be the same as either input.
- * @param [in] a Any scalar.
- * @param [in] b Any scalar.
- * @param [in] pick_b If nonzero, choose scalar b.
- */
-void decaf_255_scalar_cond_sel (
- decaf_255_scalar_t out,
- const decaf_255_scalar_t a,
- const decaf_255_scalar_t b,
- decaf_word_t pick_b
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Test that a point is valid, for debugging purposes.
- *
- * @param [in] to_test The point to test.
- * @retval DECAF_TRUE The point is valid.
- * @retval DECAF_FALSE The point is invalid.
- */
-decaf_bool_t decaf_255_point_valid (
- const decaf_255_point_t to_test
-) DECAF_API_VIS DECAF_WARN_UNUSED DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Torque a point, for debugging purposes. The output
- * will be equal to the input.
- *
- * @param [out] q The point to torque.
- * @param [in] p The point to torque.
- */
-void decaf_255_point_debugging_torque (
- decaf_255_point_t q,
- const decaf_255_point_t p
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Projectively scale a point, for debugging purposes.
- * The output will be equal to the input, and will be valid
- * even if the factor is zero.
- *
- * @param [out] q The point to scale.
- * @param [in] p The point to scale.
- * @param [in] factor Serialized GF factor to scale.
- */
-void decaf_255_point_debugging_pscale (
- decaf_255_point_t q,
- const decaf_255_point_t p,
- const unsigned char factor[DECAF_255_SER_BYTES]
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Almost-Elligator-like hash to curve.
- *
- * Call this function with the output of a hash to make a hash to the curve.
- *
- * This function runs Elligator2 on the decaf_255 Jacobi quartic model. It then
- * uses the isogeny to put the result in twisted Edwards form. As a result,
- * it is safe (cannot produce points of order 4), and would be compatible with
- * hypothetical other implementations of Decaf using a Montgomery or untwisted
- * Edwards model.
- *
- * Unlike Elligator, this function may be up to 4:1 on [0,(p-1)/2]:
- * A factor of 2 due to the isogeny.
- * A factor of 2 because we quotient out the 2-torsion.
- *
- * This makes it about 8:1 overall, or 16:1 overall on curves with cofactor 8.
- *
- * Negating the input (mod q) results in the same point. Inverting the input
- * (mod q) results in the negative point. This is the same as Elligator.
- *
- * This function isn't quite indifferentiable from a random oracle.
- * However, it is suitable for many protocols, including SPEKE and SPAKE2 EE.
- * Furthermore, calling it twice with independent seeds and adding the results
- * is indifferentiable from a random oracle.
- *
- * @param [in] hashed_data Output of some hash function.
- * @param [out] pt The data hashed to the curve.
- */
-void
-decaf_255_point_from_hash_nonuniform (
- decaf_255_point_t pt,
- const unsigned char hashed_data[DECAF_255_HASH_BYTES]
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Indifferentiable hash function encoding to curve.
- *
- * Equivalent to calling decaf_255_point_from_hash_nonuniform twice and adding.
- *
- * @param [in] hashed_data Output of some hash function.
- * @param [out] pt The data hashed to the curve.
- */
-void decaf_255_point_from_hash_uniform (
- decaf_255_point_t pt,
- const unsigned char hashed_data[2*DECAF_255_HASH_BYTES]
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE;
-
-/**
- * @brief Inverse of elligator-like hash to curve.
- *
- * This function writes to the buffer, to make it so that
- * decaf_255_point_from_hash_nonuniform(buffer) = pt if
- * possible. Since there may be multiple preimages, the
- * "which" parameter chooses between them. To ensure uniform
- * inverse sampling, this function succeeds or fails
- * independently for different "which" values.
- *
- * This function isn't guaranteed to find every possible
- * preimage, but it finds all except a small finite number.
- * In particular, when the number of bits in the modulus isn't
- * a multiple of 8 (i.e. for curve25519), it sets the high bits
- * independently, which enables the generated data to be uniform.
- * But it doesn't add p, so you'll never get exactly p from this
- * function. This might change in the future, especially if
- * we ever support eg Brainpool curves, where this could cause
- * real nonuniformity.
- *
- * @param [out] recovered_hash Encoded data.
- * @param [in] pt The point to encode.
- * @param [in] which A value determining which inverse point
- * to return.
- *
- * @retval DECAF_SUCCESS The inverse succeeded.
- * @retval DECAF_FAILURE The inverse failed.
- */
-decaf_error_t
-decaf_255_invert_elligator_nonuniform (
- unsigned char recovered_hash[DECAF_255_HASH_BYTES],
- const decaf_255_point_t pt,
- uint32_t which
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE DECAF_WARN_UNUSED;
-
-/**
- * @brief Inverse of elligator-like hash to curve.
- *
- * This function writes to the buffer, to make it so that
- * decaf_255_point_from_hash_uniform(buffer) = pt if
- * possible. Since there may be multiple preimages, the
- * "which" parameter chooses between them. To ensure uniform
- * inverse sampling, this function succeeds or fails
- * independently for different "which" values.
- *
- * @param [out] recovered_hash Encoded data.
- * @param [in] pt The point to encode.
- * @param [in] which A value determining which inverse point
- * to return.
- *
- * @retval DECAF_SUCCESS The inverse succeeded.
- * @retval DECAF_FAILURE The inverse failed.
- */
-decaf_error_t
-decaf_255_invert_elligator_uniform (
- unsigned char recovered_hash[2*DECAF_255_HASH_BYTES],
- const decaf_255_point_t pt,
- uint32_t which
-) DECAF_API_VIS DECAF_NONNULL DECAF_NOINLINE DECAF_WARN_UNUSED;
-
-/**
- * @brief Overwrite scalar with zeros.
- */
-void decaf_255_scalar_destroy (
- decaf_255_scalar_t scalar
-) DECAF_NONNULL DECAF_API_VIS;
-
-/**
- * @brief Overwrite point with zeros.
- */
-void decaf_255_point_destroy (
- decaf_255_point_t point
-) DECAF_NONNULL DECAF_API_VIS;
-
-/**
- * @brief Overwrite precomputed table with zeros.
- */
-void decaf_255_precomputed_destroy (
- decaf_255_precomputed_s *pre
-) DECAF_NONNULL DECAF_API_VIS;
-
-#ifdef __cplusplus
-} /* extern "C" */
-#endif
-
-#endif /* __DECAF_POINT_255_H__ */
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