openssl_sign

(PHP 4 >= 4.0.4, PHP 5, PHP 7, PHP 8)

openssl_sign — Generate signature

Description

openssl_sign(
    string $data,
    string &$signature,
    #[\SensitiveParameter] OpenSSLAsymmetricKey|OpenSSLCertificate|array|string $private_key,
    string|int $algorithm = OPENSSL_ALGO_SHA1
): bool

openssl_sign() computes a signature for the specified data by generating a cryptographic digital signature using the private key associated with private_key. Note that the data itself is not encrypted.

Parameters

data

The string of data you wish to sign

signature

If the call was successful the signature is returned in signature.

private_key

OpenSSLAsymmetricKey - a key, returned by openssl_get_privatekey()

string - a PEM formatted key

algorithm

int - one of these Signature Algorithms.

string - a valid string returned by openssl_get_md_methods() example, "sha256WithRSAEncryption" or "sha384".

Return Values

Returns true on success or false on failure.

Changelog

Version	Description
8.0.0	`private_key` accepts an OpenSSLAsymmetricKey or OpenSSLCertificate instance now; previously, a resource of type `OpenSSL key` or `OpenSSL X.509` was accepted.

Examples

Example #1 openssl_sign() example

<?php
// $data is assumed to contain the data to be signed

// fetch private key from file and ready it
$pkeyid = openssl_pkey_get_private("file://src/openssl-0.9.6/demos/sign/key.pem");

// compute signature
openssl_sign($data, $signature, $pkeyid);

// free the key from memory
openssl_free_key($pkeyid);
?>

Example #2 openssl_sign() example

<?php
//data you want to sign
$data = 'my data';

//create new private and public key
$new_key_pair = openssl_pkey_new(array(
    "private_key_bits" => 2048,
    "private_key_type" => OPENSSL_KEYTYPE_RSA,
));
openssl_pkey_export($new_key_pair, $private_key_pem);

$details = openssl_pkey_get_details($new_key_pair);
$public_key_pem = $details['key'];

//create signature
openssl_sign($data, $signature, $private_key_pem, OPENSSL_ALGO_SHA256);

//save for later
file_put_contents('private_key.pem', $private_key_pem);
file_put_contents('public_key.pem', $public_key_pem);
file_put_contents('signature.dat', $signature);

//verify signature
$r = openssl_verify($data, $signature, $public_key_pem, "sha256WithRSAEncryption");
var_dump($r);
?>

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User Contributed Notes 2 notes

down

edmarw at yahoo dot com ¶

17 years ago

This may help if you just want a real-simple private/public key pair:

<?php

$data = "Beeeeer is really good.. hic...";

// You can get a simple private/public key pair using:
// openssl genrsa 512 >private_key.txt
// openssl rsa -pubout <private_key.txt >public_key.txt

// IMPORTANT: The key pair below is provided for testing only. 
// For security reasons you must get a new key pair
// for production use, obviously.

$private_key = <<<EOD
-----BEGIN RSA PRIVATE KEY-----
MIIBOgIBAAJBANDiE2+Xi/WnO+s120NiiJhNyIButVu6zxqlVzz0wy2j4kQVUC4Z
RZD80IY+4wIiX2YxKBZKGnd2TtPkcJ/ljkUCAwEAAQJAL151ZeMKHEU2c1qdRKS9
sTxCcc2pVwoAGVzRccNX16tfmCf8FjxuM3WmLdsPxYoHrwb1LFNxiNk1MXrxjH3R
6QIhAPB7edmcjH4bhMaJBztcbNE1VRCEi/bisAwiPPMq9/2nAiEA3lyc5+f6DEIJ
h1y6BWkdVULDSM+jpi1XiV/DevxuijMCIQCAEPGqHsF+4v7Jj+3HAgh9PU6otj2n
Y79nJtCYmvhoHwIgNDePaS4inApN7omp7WdXyhPZhBmulnGDYvEoGJN66d0CIHra
I2SvDkQ5CmrzkW5qPaE2oO7BSqAhRZxiYpZFb5CI
-----END RSA PRIVATE KEY-----
EOD;
$public_key = <<<EOD
-----BEGIN PUBLIC KEY-----
MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBANDiE2+Xi/WnO+s120NiiJhNyIButVu6
zxqlVzz0wy2j4kQVUC4ZRZD80IY+4wIiX2YxKBZKGnd2TtPkcJ/ljkUCAwEAAQ==
-----END PUBLIC KEY-----
EOD;

$binary_signature = "";

// At least with PHP 5.2.2 / OpenSSL 0.9.8b (Fedora 7)
// there seems to be no need to call openssl_get_privatekey or similar.
// Just pass the key as defined above
openssl_sign($data, $binary_signature, $private_key, OPENSSL_ALGO_SHA1);

// Check signature
$ok = openssl_verify($data, $binary_signature, $public_key, OPENSSL_ALGO_SHA1);
echo "check #1: ";
if ($ok == 1) {
    echo "signature ok (as it should be)\n";
} elseif ($ok == 0) {
    echo "bad (there's something wrong)\n";
} else {
    echo "ugly, error checking signature\n";
}

$ok = openssl_verify('tampered'.$data, $binary_signature, $public_key, OPENSSL_ALGO_SHA1);
echo "check #2: ";
if ($ok == 1) {
    echo "ERROR: Data has been tampered, but signature is still valid! Argh!\n";
} elseif ($ok == 0) {
    echo "bad signature (as it should be, since data has beent tampered)\n";
} else {
    echo "ugly, error checking signature\n";
}

?>