Generate signature

# 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`,
int `$padding` = 0
): 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".

`padding`
  RSA PSS padding to use.

### Return Values

Returns `true` on success or `false` on failure.

### Changelog

Version | Description
--- | ---
8.5.0 | The optional parameter `padding` has been added.
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);
?>`

### See Also

- openssl_verify() - Verify signature

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