include/hash_to_field.h.in

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Unless required by applicable law or agreed to in writing,
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*/

/**
 * @file hash_to_field.h
 * 
 * @author Alexandre Adomnicai
 * 
 * @brief Header file for implementation of standard hash to curve functions according to https://datatracker.ietf.org/doc/draft-irtf-cfrg-hash-to-curve/
 */
#ifndef HASH_TO_FIELD_ZZZ_H
#define HASH_TO_FIELD_ZZZ_H

#include "fp_YYY.h"
#include "config_curve_ZZZ.h"

#define SUCCESS                    0x00000000
#define ERR_NULLPOINTER_HASH2FIELD 0x00000401
#define ERR_BADARGLEN_HASH2FIELD   0x00000402

/** 
 * @brief Hash a byte string msg of arbitrary length into one or more finite
 * field elements according to the draft-irtf-cfrg-hash-to-curve-16 spec.
 * Relies on expand_message_xmd function with SHA-256.
 * 
 * @param elems Output finite field elements
 * @param nelems Number of finite field elements (is 'count * m' from spec)
 * @param m Extension degree of finite field (m >= 1)
 * @param msg Input byte string
 * @param msglen Byte string length (in bytes)
 * @param DST Domain separation tag
 * @param DSTlen Domain separation tag length (in bytes)
 * 
 * @return 0 if successful, error code otherwise
 */
extern int hash_to_field_YYY(BIG_XXX elems[], unsigned int nelems, unsigned int m,
  const char *msg, unsigned int msglen,
  const char *DST, unsigned int DSTlen);

#endif