PHP 7.0.6 Released

    openssl_sign

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

    openssl_sign — Generate signature

    Description

    bool openssl_sign ( string $data , string &$signature , mixed $priv_key_id [, mixed $signature_alg = OPENSSL_ALGO_SHA1 ] )

    openssl_sign() computes a signature for the specified data by generating a cryptographic digital signature using the private key associated with priv_key_id. 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.

    priv_key_id

    resource - a key, returned by openssl_get_privatekey()

    string - a PEM formatted key

    signature_alg

    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.

    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);
    ?>

    See Also

    User Contributed Notes

    Chris Kistner
    5 years ago
    The list of Signature Algorithms (constants) is very limited! Fortunately the newer versions of php/openssl allow you to specify the signature algorithm as a string.

    You can use the 'openssl_get_md_methods' method to get a list of digest methods. Only some of them may be used to sign with RSA private keys.

    Those that can be used to sign with RSA private keys are: md4, md5, ripemd160, sha, sha1, sha224, sha256, sha384, sha512

    Here's the modified Example #1 with SHA-512 hash:
    <?php
    // $data is assumed to contain the data to be signed

    // fetch private key from file and ready it
    $fp = fopen("/src/openssl-0.9.6/demos/sign/key.pem", "r");
    $priv_key = fread($fp, 8192);
    fclose($fp);
    $pkeyid = openssl_get_privatekey($priv_key);

    // compute signature with SHA-512
    openssl_sign($data, $signature, $pkeyid, "sha512");

    // free the key from memory
    openssl_free_key($pkeyid);
    ?>
    adam dot mansfeld at gmail dot com
    10 years ago
    Hello,

    the fourth parameter 'signature_alg' to choose the signature algorithm can be one of:

    OPENSSL_ALGO_SHA1
    OPENSSL_ALGO_MD5
    OPENSSL_ALGO_MD4
    OPENSSL_ALGO_MD2

    Just for the case that somebody needs this.

    Regards
    edmarw at yahoo dot com
    8 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";
    }

    ?>
    To Top