/**
* @file decaf/ed448.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 Ed448-Goldilocks.
*
* @warning This file was automatically generated in Python.
* Please do not edit it.
*/
#ifndef __DECAF_ED448_H__
#define __DECAF_ED448_H__ 1
#include "point_448.h"
#include "shake.h"
#ifdef __cplusplus
extern "C" {
#endif
/** Number of bytes in an EdDSA public key. */
#define DECAF_EDDSA_448_PUBLIC_BYTES 57
/** Number of bytes in an EdDSA private key. */
#define DECAF_EDDSA_448_PRIVATE_BYTES DECAF_EDDSA_448_PUBLIC_BYTES
/** Number of bytes in an EdDSA private key. */
#define DECAF_EDDSA_448_SIGNATURE_BYTES (DECAF_EDDSA_448_PUBLIC_BYTES + DECAF_EDDSA_448_PRIVATE_BYTES)
/** Does EdDSA support non-contextual signatures? */
#define DECAF_EDDSA_448_SUPPORTS_CONTEXTLESS_SIGS 0
/** Prehash context renaming macros. */
#define decaf_ed448_prehash_ctx_s decaf_shake256_ctx_s
#define decaf_ed448_prehash_ctx_t decaf_shake256_ctx_t
#define decaf_ed448_prehash_update decaf_shake256_update
#define decaf_ed448_prehash_destroy decaf_shake256_destroy
/** EdDSA encoding ratio. */
#define DECAF_448_EDDSA_ENCODE_RATIO 4
/** EdDSA decoding ratio. */
#define DECAF_448_EDDSA_DECODE_RATIO (4 / 4)
/**
* @brief EdDSA key generation. This function uses a different (non-Decaf)
* encoding.
*
* @param [out] pubkey The public key.
* @param [in] privkey The private key.
*/
void decaf_ed448_derive_public_key (
uint8_t pubkey[DECAF_EDDSA_448_PUBLIC_BYTES],
const uint8_t privkey[DECAF_EDDSA_448_PRIVATE_BYTES]
);
/**
* @brief EdDSA signing.
*
* @param [out] signature The signature.
* @param [in] privkey The private key.
* @param [in] pubkey The public key.
* @param [in] message The message to sign.
* @param [in] message_len The length of the message.
* @param [in] prehashed Nonzero if the message is actually the hash of something you want to sign.
* @param [in] context A "context" for this signature of up to 255 bytes.
* @param [in] context_len Length of the context.
*
* @warning For Ed25519, it is unsafe to use the same key for both prehashed and non-prehashed
* messages, at least without some very careful protocol-level disambiguation. For Ed448 it is
* safe. The C++ wrapper is designed to make it harder to screw this up, but this C code gives
* you no seat belt.
*/
void decaf_ed448_sign (
uint8_t signature[DECAF_EDDSA_448_SIGNATURE_BYTES],
const uint8_t privkey[DECAF_EDDSA_448_PRIVATE_BYTES],
const uint8_t pubkey[DECAF_EDDSA_448_PUBLIC_BYTES],
const uint8_t *message,
size_t message_len,
uint8_t prehashed,
const uint8_t *context,
uint8_t context_len
) __attribute__((nonnull(1,2,3)));
/**
* @brief EdDSA signing with prehash.
*
* @param [out] signature The signature.
* @param [in] privkey The private key.
* @param [in] pubkey The public key.
* @param [in] hash The hash of the message. This object will not be modified by the call.
* @param [in] context A "context" for this signature of up to 255 bytes. Must be the same as what was used for the prehash.
* @param [in] context_len Length of the context.
*
* @warning For Ed25519, it is unsafe to use the same key for both prehashed and non-prehashed
* messages, at least without some very careful protocol-level disambiguation. For Ed448 it is
* safe. The C++ wrapper is designed to make it harder to screw this up, but this C code gives
* you no seat belt.
*/
void decaf_ed448_sign_prehash (
uint8_t signature[DECAF_EDDSA_448_SIGNATURE_BYTES],
const uint8_t privkey[DECAF_EDDSA_448_PRIVATE_BYTES],
const uint8_t pubkey[DECAF_EDDSA_448_PUBLIC_BYTES],
const uint8_t hash[64],
const uint8_t *context,
uint8_t context_len
) __attribute__((nonnull(1,2,3,4)));
/**
* @brief Prehash initialization, with contexts if supported.
*
* @param [out] hash The hash object to be initialized.
*/
void decaf_ed448_prehash_init (
decaf_ed448_prehash_ctx_t hash
) __attribute__((nonnull(1)));
/**
* @brief EdDSA signature verification.
*
* Uses the standard (i.e. less-strict) verification formula.
*
* @param [in] signature The signature.
* @param [in] pubkey The public key.
* @param [in] message The message to verify.
* @param [in] message_len The length of the message.
* @param [in] prehashed Nonzero if the message is actually the hash of something you want to verify.
* @param [in] context A "context" for this signature of up to 255 bytes.
* @param [in] context_len Length of the context.
*
* @warning For Ed25519, it is unsafe to use the same key for both prehashed and non-prehashed
* messages, at least without some very careful protocol-level disambiguation. For Ed448 it is
* safe. The C++ wrapper is designed to make it harder to screw this up, but this C code gives
* you no seat belt.
*/
decaf_error_t decaf_ed448_verify (
const uint8_t signature[DECAF_EDDSA_448_SIGNATURE_BYTES],
const uint8_t pubkey[DECAF_EDDSA_448_PUBLIC_BYTES],
const uint8_t *message,
size_t message_len,
uint8_t prehashed,
const uint8_t *context,
uint8_t context_len
) __attribute__((nonnull(1,2)));
/**
* @brief EdDSA signature verification.
*
* Uses the standard (i.e. less-strict) verification formula.
*
* @param [in] signature The signature.
* @param [in] pubkey The public key.
* @param [in] hash The hash of the message. This object will not be modified by the call.
* @param [in] context A "context" for this signature of up to 255 bytes. Must be the same as what was used for the prehash.
* @param [in] context_len Length of the context.
*
* @warning For Ed25519, it is unsafe to use the same key for both prehashed and non-prehashed
* messages, at least without some very careful protocol-level disambiguation. For Ed448 it is
* safe. The C++ wrapper is designed to make it harder to screw this up, but this C code gives
* you no seat belt.
*/
decaf_error_t decaf_ed448_verify_prehash (
const uint8_t signature[DECAF_EDDSA_448_SIGNATURE_BYTES],
const uint8_t pubkey[DECAF_EDDSA_448_PUBLIC_BYTES],
const uint8_t hash[64],
const uint8_t *context,
uint8_t context_len
) __attribute__((nonnull(1,2)));
/**
* @brief EdDSA point encoding. Used internally, exposed externally.
* Multiplies by DECAF_448_EDDSA_ENCODE_RATIO first.
*
* The multiplication is required because the EdDSA encoding represents
* the cofactor information, but the Decaf encoding ignores it (which
* is the whole point). So if you decode from EdDSA and re-encode to
* EdDSA, the cofactor info must get cleared, because the intermediate
* representation doesn't track it.
*
* The way libdecaf handles this is to multiply by
* DECAF_448_EDDSA_DECODE_RATIO when decoding, and by
* DECAF_448_EDDSA_ENCODE_RATIO when encoding. The product of these
* ratios is always exactly the cofactor 4, so the cofactor
* ends up cleared one way or another. But exactly how that shakes
* out depends on the base points specified in RFC 8032.
*
* The upshot is that if you pass the Decaf/Ristretto base point to
* this function, you will get DECAF_448_EDDSA_ENCODE_RATIO times the
* EdDSA base point.
*
* @param [out] enc The encoded point.
* @param [in] p The point.
*/
void curve448_point_mul_by_ratio_and_encode_like_eddsa (
uint8_t enc[DECAF_EDDSA_448_PUBLIC_BYTES],
const curve448_point_t p
);
/**
* @brief EdDSA point decoding. Multiplies by DECAF_448_EDDSA_DECODE_RATIO,
* and ignores cofactor information.
*
* See notes on curve448_point_mul_by_ratio_and_encode_like_eddsa
*
* @param [out] enc The encoded point.
* @param [in] p The point.
*/
decaf_error_t curve448_point_decode_like_eddsa_and_mul_by_ratio (
curve448_point_t p,
const uint8_t enc[DECAF_EDDSA_448_PUBLIC_BYTES]
);
/**
* @brief EdDSA to ECDH public key conversion
* Deserialize the point to get y on Edwards curve,
* Convert it to u coordinate on Montgomery curve.
*
* @warning This function does not check that the public key being converted
* is a valid EdDSA public key (FUTURE?)
*
* @param[out] x The ECDH public key as in RFC7748(point on Montgomery curve)
* @param[in] ed The EdDSA public key(point on Edwards curve)
*/
void decaf_ed448_convert_public_key_to_x448 (
uint8_t x[DECAF_X448_PUBLIC_BYTES],
const uint8_t ed[DECAF_EDDSA_448_PUBLIC_BYTES]
);
/**
* @brief EdDSA to ECDH private key conversion
* Using the appropriate hash function, hash the EdDSA private key
* and keep only the lower bytes to get the ECDH private key
*
* @param[out] x The ECDH private key as in RFC7748
* @param[in] ed The EdDSA private key
*/
void decaf_ed448_convert_private_key_to_x448 (
uint8_t x[DECAF_X448_PRIVATE_BYTES],
const uint8_t ed[DECAF_EDDSA_448_PRIVATE_BYTES]
);
#ifdef __cplusplus
} /* extern "C" */
#endif
#endif /* __DECAF_ED448_H__ */