ECDSA_SIG_NEW(3SSL)

📦
version 4.0.3 · 14 versions
, in ubuntu stonking

🌸 ECDSA_SIG_NEW 💅 (that's the 3SSL manual, bestie, OpenSSL fam)

okay so. sit down, grab a boba, because we're talking about ECDSA_SIG objects and honestly? they're lowkey iconic once you get them.

✨ NAME ✨

ECDSA_SIG_new, ECDSA_SIG_free, ECDSA_SIG_get0, ECDSA_SIG_get0_r, ECDSA_SIG_get0_s, ECDSA_SIG_set0 — the whole girliesquad of functions for creating, destroying and manipulating ECDSA_SIG objects. 🫶

🌈 SYNOPSIS 🌈

#include <openssl/ecdsa.h>

ECDSA_SIG *ECDSA_SIG_new(void);
void ECDSA_SIG_free(ECDSA_SIG *sig);
void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps);
const BIGNUM *ECDSA_SIG_get0_r(const ECDSA_SIG *sig);
const BIGNUM *ECDSA_SIG_get0_s(const ECDSA_SIG *sig);
int ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s);

💖 DESCRIPTION 💖

So. ECDSA_SIG is an opaque structure made of two BIGNUMs — one for the r value and one for the s value of an Elliptic Curve Digital Signature Algorithm (ECDSA) signature. (if you wanna go read the receipts, that's FIPS186-4 or X9.62 📚)

The ECDSA_SIG object was mainly used by the deprecated low level functions described in ECDSA_sign(3) — rip to those, they had a good run 😭 — but it's still required if you wanna be able to set or get the values of r and s into or from a signature. This is mainly used for testing purposes, as shown in the "EXAMPLES" below. periodt.

  • ECDSA_SIG_new() — allocates an empty ECDSA_SIG structure. Note: before OpenSSL 1.1.0, the r and s components were initialised. so if you're time-travelling back to old versions, vibe check accordingly ⏳
  • ECDSA_SIG_free() — frees the ECDSA_SIG structure sig. If the argument is NULL, nothing is done. she simply does not care 💅
  • ECDSA_SIG_get0() — returns internal pointers the r and s values contained in sig and stores them in *pr and *ps, respectively. The pointer pr or ps can be NULL, in which case the corresponding value is not returned. no drama, no problem.
  • ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s() — the values r, s can also be retrieved separately by these corresponding functions, respectively. they're giving "I work better alone" energy 🦋
  • ECDSA_SIG_set0() — Non-NULL r and s values can be set on the sig by calling this. Calling this function transfers the memory management of the values to the ECDSA_SIG object, and therefore the values that have been passed in should not be freed by the caller. do NOT double-free her, bestie, that's the one rule 🚨
For info about encoding and decoding ECDSA signatures to/from DER, go see i2d_ECDSA_SIG(3) and d2i_ECDSA_SIG(3). 💌

🌟 RETURN VALUES 🌟

  • ECDSA_SIG_new() returns NULL if the allocation fails. (booo 🍅)
  • ECDSA_SIG_set0() returns 1 on success or 0 on failure. iconic binary behaviour.
  • ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s() return the corresponding value, or NULL if it is unset. slay or nothing.

🧚 EXAMPLES 🧚

💜 Example 1: Extract signature r and s values from a ECDSA signature of size signaturelen

ECDSA_SIG *obj;
const BIGNUM *r, *s;

/* Load a signature into the ECDSA_SIG object */
obj = d2i_ECDSA_SIG(NULL, &signature, signaturelen);
if (obj == NULL)
    /* error */

r = ECDSA_SIG_get0_r(obj);
s = ECDSA_SIG_get0_s(obj);
if (r == NULL || s == NULL)
    /* error */

/* Use BN_bn2binpad() here to convert to r and s into byte arrays */

/*
 * Do not try to access I<r> or I<s> after calling ECDSA_SIG_free(),
 * as they are both freed by this call.
 */
ECDSA_SIG_free(obj);
⚠️ real talk: do NOT try to access r or s after calling ECDSA_SIG_free(), because they are both freed by that call. they are gone. deceased. no cap. 💀

💜 Example 2: Convert r and s byte arrays into an ECDSA_SIG signature of size signaturelen

ECDSA_SIG *obj = NULL;
unsigned char *signature = NULL;
size_t signaturelen;
BIGNUM *rbn = NULL, *sbn = NULL;

obj = ECDSA_SIG_new();
if (obj == NULL)
    /* error */
rbn = BN_bin2bn(r, rlen, NULL);
sbn = BN_bin2bn(s, slen, NULL);
if (rbn == NULL || sbn == NULL)
    /* error */

if (!ECDSA_SIG_set0(obj, rbn, sbn))
    /* error */
/* Set these to NULL since they are now owned by obj */
rbn = sbn = NULL;

signaturelen = i2d_ECDSA_SIG(obj, &signature);
if (signaturelen <= 0)
    /* error */

/*
 * This signature could now be passed to L<EVP_DigestVerify(3)>
 * or L<EVP_DigestVerifyFinal(3)>
 */

BN_free(rbn);
BN_free(sbn);
OPENSSL_free(signature);
ECDSA_SIG_free(obj);

👑 CONFORMING TO 👑

ANSI X9.62, US Federal Information Processing Standard FIPS186-4 (Digital Signature Standard, DSS). we stay standards-compliant, bestie 🎀

🔥 SEE ALSO 🔥

EC_KEY_new(3), EVP_DigestSignInit(3), EVP_DigestVerifyInit(3), EVP_PKEY_sign(3) i2d_ECDSA_SIG(3), d2i_ECDSA_SIG(3), ECDSA_sign(3)

(go read those too, they're all part of the extended universe 🌌)

Copyright 2004-2024 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

and that's the whole thing!! this page was living in version 4.0.3, dated 2026-09-29, under the ECDSA_SIG_NEW(3SSL) header 💖✨ go write some signatures, queen 👑🦋🌸

📦 where this page comes from