frosix

Multiparty signature service (experimental)
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high_common.h (4534B)

      1 /*
      2   This file is part of Frosix
      3   Copyright (C) 2022, 2023 Frosix
      4 
      5   Frosix is free software; you can redistribute it and/or modify it under the
      6   terms of the GNU Affero General Public License as published by the Free Software
      7   Foundation; either version 3, or (at your option) any later version.
      8 
      9   Frosix is distributed in the hope that it will be useful, but WITHOUT ANY
     10   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
     11   A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.
     12 
     13   You should have received a copy of the GNU Affero General Public License along with
     14   Frosix; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
     15 */
     16 /**
     17  * @file high_common.h
     18  * @brief Provides functions which are used for different tasks during the signing or key generation process.
     19  * @author Joel Urech
     20 */
     21 #ifndef FROST_HIGH_COMMON_H
     22 #define FROST_HIGH_COMMON_H
     23 
     24 #include "frost_high.h"
     25 
     26 /**
     27  * Struct for a binding factor
     28 */
     29 struct FROST_BindingFactor
     30 {
     31   /**
     32    * For which participant is this binding factor?
     33   */
     34   uint8_t identifier;
     35   /**
     36    * The binding factor
     37   */
     38   struct FROST_Scalar binding_factor;
     39 };
     40 
     41 /**
     42  * Struct for a group commitment
     43 */
     44 struct FROST_GroupCommitment
     45 {
     46   /**
     47    * Our group commitment is a point on the curve
     48   */
     49   struct FROST_Point commitment;
     50 };
     51 
     52 /**
     53  * Struct for the lagrange coefficient
     54 */
     55 struct FROST_Coefficient
     56 {
     57   /**
     58    * Our lagrange coefficient is a FROST_Scalar
     59   */
     60   struct FROST_Scalar coeff;
     61 };
     62 
     63 /**
     64  * Struct for the signature challenge
     65 */
     66 struct FROST_Challenge
     67 {
     68   /**
     69    * Our challenge is a hash, mapped to a scalar in range of the order of the ristretto255 group
     70   */
     71   struct FROST_Scalar challenge;
     72 };
     73 
     74 /**
     75  * @brief Computes the set of binding values for all participating participants.
     76  *
     77  * @param[out] binding_factors The resulting set of binding factors
     78  * @param[in] commitments Array of all commitments
     79  * @param commitments_len Length of commitments array
     80  * @param[in] mh The message we have to sign
     81  */
     82 void
     83 FROST_compute_binding_factors_ (
     84   struct FROST_BindingFactor binding_factors[],
     85   const struct FROST_Commitment commitments[],
     86   uint8_t commitments_len,
     87   const struct FROST_MessageHash *mh);
     88 
     89 /**
     90  * @brief Computes the group commitment.
     91  *
     92  * @param[out] group_commitment The resulting group commitment
     93  * @param[in] commitments List of all commitments
     94  * @param[in] binding_factors Set of all binding factors
     95  * @param comm_and_bind_len Number of elements in commitments and binding_factors
     96  */
     97 void FROST_compute_group_commitment_ (
     98   struct FROST_GroupCommitment *group_commitment,
     99   const struct FROST_Commitment commitments[],
    100   const struct FROST_BindingFactor binding_factors[],
    101   uint8_t comm_and_bind_len);
    102 
    103 /**
    104  * @brief Returns the binding factor of a specific participant.
    105  *
    106  * @param[out] binding_factor The found binding factor
    107  * @param[in] binding_factors Set of all binding factors
    108  * @param binding_factors_len Number of elements in binding_factors
    109  * @param participant The participant for whom we are looking for the binding factor
    110  * @return GNUNET_OK if a binding factor was found, otherwise GNUNET_NO
    111 */
    112 enum GNUNET_GenericReturnValue
    113 FROST_binding_factor_for_participant_ (
    114   struct FROST_BindingFactor *binding_factor,
    115   const struct FROST_BindingFactor binding_factors[],
    116   uint8_t binding_factors_len,
    117   uint8_t participant);
    118 
    119 /**
    120  * @brief Computes the lagrange coefficient for a specific participant.
    121  *
    122  * @param[out] coefficient The resulting lagrange coefficient
    123  * @param[in] participant The participant for which we need the lagrange coefficient
    124  * @param[in] commitments List of all commitments. We only need the identifiers of the participants from it
    125  * @param commitments_len Length of commitment list
    126  * @return 1 if success, otherwise 0
    127 */
    128 enum GNUNET_GenericReturnValue
    129 FROST_compute_lagrange_coefficient_ (
    130   struct FROST_Coefficient *coefficient,
    131   uint8_t participant,
    132   const struct FROST_Commitment commitments[],
    133   size_t commitments_len);
    134 
    135 /**
    136  * @brief Computes the signature challenge
    137  *
    138  * @param[out] challenge The resulting challenge
    139  * @param[in] group_commitment A previously computed group commitment
    140  * @param[in] group_pk Public key of the signing group
    141  * @param[in] mh Our hash of the message we have to sign
    142 */
    143 void
    144 FROST_compute_challenge_ (
    145   struct FROST_Challenge *challenge,
    146   const struct FROST_GroupCommitment *group_commitment,
    147   const struct FROST_PublicKey *group_pk,
    148   const struct FROST_MessageHash *mh);
    149 
    150 #endif