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How set (or get after signing) random number for function openssl_sign?

$pkEcPem = "-----BEGIN EC PRIVATE KEY-----302e0201010420...a00706052b8104000a-----END EC PRIVATE KEY-----"
$pk = openssl_pkey_get_private($pkEcPem);
$signature = null;
openssl_sign($message, $signature, $pk, $algo);
openssl_free_key($pk);

Example of implementation in the PHP library https://github.com/phpecc/phpecc/blob/master/src/Crypto/Signature/Signer.php#L36

Variant names of this value

  • random Key
  • random Number
  • random Point
Improve this question
2
  • The fact that k (the random number) must be generated explicitly is a peculiarity of the linked library. Depending on the value of k, the library controls in this way whether the non-deterministic ECDSA variant (arbitrary k) or the deterministic ECDSA variant (determination of k according to RFC6979) is used (see the ECDSA sample). Commented Apr 8, 2024 at 9:46
  • In most libraries, the generation of k takes place internally (and is not carried out by the user) and different methods or a flag are used to distinguish between the two variants (if the library offers both variants at all). AFAIK, openssl_sign() only supports non-deterministic ECDSA. For deterministic ECDSA you have to use a different library. Commented Apr 8, 2024 at 9:49
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