github.com/guiltylotus/go-ethereum@v1.9.7/crypto/secp256k1/ext.h (about)

     1  // Copyright 2015 Jeffrey Wilcke, Felix Lange, Gustav Simonsson. All rights reserved.
     2  // Use of this source code is governed by a BSD-style license that can be found in
     3  // the LICENSE file.
     4  
     5  // secp256k1_context_create_sign_verify creates a context for signing and signature verification.
     6  static secp256k1_context* secp256k1_context_create_sign_verify() {
     7  	return secp256k1_context_create(SECP256K1_CONTEXT_SIGN | SECP256K1_CONTEXT_VERIFY);
     8  }
     9  
    10  // secp256k1_ext_ecdsa_recover recovers the public key of an encoded compact signature.
    11  //
    12  // Returns: 1: recovery was successful
    13  //          0: recovery was not successful
    14  // Args:    ctx:        pointer to a context object (cannot be NULL)
    15  //  Out:    pubkey_out: the serialized 65-byte public key of the signer (cannot be NULL)
    16  //  In:     sigdata:    pointer to a 65-byte signature with the recovery id at the end (cannot be NULL)
    17  //          msgdata:    pointer to a 32-byte message (cannot be NULL)
    18  static int secp256k1_ext_ecdsa_recover(
    19  	const secp256k1_context* ctx,
    20  	unsigned char *pubkey_out,
    21  	const unsigned char *sigdata,
    22  	const unsigned char *msgdata
    23  ) {
    24  	secp256k1_ecdsa_recoverable_signature sig;
    25  	secp256k1_pubkey pubkey;
    26  
    27  	if (!secp256k1_ecdsa_recoverable_signature_parse_compact(ctx, &sig, sigdata, (int)sigdata[64])) {
    28  		return 0;
    29  	}
    30  	if (!secp256k1_ecdsa_recover(ctx, &pubkey, &sig, msgdata)) {
    31  		return 0;
    32  	}
    33  	size_t outputlen = 65;
    34  	return secp256k1_ec_pubkey_serialize(ctx, pubkey_out, &outputlen, &pubkey, SECP256K1_EC_UNCOMPRESSED);
    35  }
    36  
    37  // secp256k1_ext_ecdsa_verify verifies an encoded compact signature.
    38  //
    39  // Returns: 1: signature is valid
    40  //          0: signature is invalid
    41  // Args:    ctx:        pointer to a context object (cannot be NULL)
    42  //  In:     sigdata:    pointer to a 64-byte signature (cannot be NULL)
    43  //          msgdata:    pointer to a 32-byte message (cannot be NULL)
    44  //          pubkeydata: pointer to public key data (cannot be NULL)
    45  //          pubkeylen:  length of pubkeydata
    46  static int secp256k1_ext_ecdsa_verify(
    47  	const secp256k1_context* ctx,
    48  	const unsigned char *sigdata,
    49  	const unsigned char *msgdata,
    50  	const unsigned char *pubkeydata,
    51  	size_t pubkeylen
    52  ) {
    53  	secp256k1_ecdsa_signature sig;
    54  	secp256k1_pubkey pubkey;
    55  
    56  	if (!secp256k1_ecdsa_signature_parse_compact(ctx, &sig, sigdata)) {
    57  		return 0;
    58  	}
    59  	if (!secp256k1_ec_pubkey_parse(ctx, &pubkey, pubkeydata, pubkeylen)) {
    60  		return 0;
    61  	}
    62  	return secp256k1_ecdsa_verify(ctx, &sig, msgdata, &pubkey);
    63  }
    64  
    65  // secp256k1_ext_reencode_pubkey decodes then encodes a public key. It can be used to
    66  // convert between public key formats. The input/output formats are chosen depending on the
    67  // length of the input/output buffers.
    68  //
    69  // Returns: 1: conversion successful
    70  //          0: conversion unsuccessful
    71  // Args:    ctx:        pointer to a context object (cannot be NULL)
    72  //  Out:    out:        output buffer that will contain the reencoded key (cannot be NULL)
    73  //  In:     outlen:     length of out (33 for compressed keys, 65 for uncompressed keys)
    74  //          pubkeydata: the input public key (cannot be NULL)
    75  //          pubkeylen:  length of pubkeydata
    76  static int secp256k1_ext_reencode_pubkey(
    77  	const secp256k1_context* ctx,
    78  	unsigned char *out,
    79  	size_t outlen,
    80  	const unsigned char *pubkeydata,
    81  	size_t pubkeylen
    82  ) {
    83  	secp256k1_pubkey pubkey;
    84  
    85  	if (!secp256k1_ec_pubkey_parse(ctx, &pubkey, pubkeydata, pubkeylen)) {
    86  		return 0;
    87  	}
    88  	unsigned int flag = (outlen == 33) ? SECP256K1_EC_COMPRESSED : SECP256K1_EC_UNCOMPRESSED;
    89  	return secp256k1_ec_pubkey_serialize(ctx, out, &outlen, &pubkey, flag);
    90  }
    91  
    92  // secp256k1_ext_scalar_mul multiplies a point by a scalar in constant time.
    93  //
    94  // Returns: 1: multiplication was successful
    95  //          0: scalar was invalid (zero or overflow)
    96  // Args:    ctx:      pointer to a context object (cannot be NULL)
    97  //  Out:    point:    the multiplied point (usually secret)
    98  //  In:     point:    pointer to a 64-byte public point,
    99  //                    encoded as two 256bit big-endian numbers.
   100  //          scalar:   a 32-byte scalar with which to multiply the point
   101  int secp256k1_ext_scalar_mul(const secp256k1_context* ctx, unsigned char *point, const unsigned char *scalar) {
   102  	int ret = 0;
   103  	int overflow = 0;
   104  	secp256k1_fe feX, feY;
   105  	secp256k1_gej res;
   106  	secp256k1_ge ge;
   107  	secp256k1_scalar s;
   108  	ARG_CHECK(point != NULL);
   109  	ARG_CHECK(scalar != NULL);
   110  	(void)ctx;
   111  
   112  	secp256k1_fe_set_b32(&feX, point);
   113  	secp256k1_fe_set_b32(&feY, point+32);
   114  	secp256k1_ge_set_xy(&ge, &feX, &feY);
   115  	secp256k1_scalar_set_b32(&s, scalar, &overflow);
   116  	if (overflow || secp256k1_scalar_is_zero(&s)) {
   117  		ret = 0;
   118  	} else {
   119  		secp256k1_ecmult_const(&res, &ge, &s);
   120  		secp256k1_ge_set_gej(&ge, &res);
   121  		/* Note: can't use secp256k1_pubkey_save here because it is not constant time. */
   122  		secp256k1_fe_normalize(&ge.x);
   123  		secp256k1_fe_normalize(&ge.y);
   124  		secp256k1_fe_get_b32(point, &ge.x);
   125  		secp256k1_fe_get_b32(point+32, &ge.y);
   126  		ret = 1;
   127  	}
   128  	secp256k1_scalar_clear(&s);
   129  	return ret;
   130  }