Digital Signature¶
A digital signature is a method to ensure that a message was sent by a specific recipient. It uses mathematical methods to combine the original message, plain text or not, with a private key, to produce a piece of data which may be verified later with the public key. Then, the pair private key and public key gives a high level of confidence that the message was coming from the known sender.
PHP can sign data with openssl and sodium extensions.
A checksum can be considered a signature without a private key: it computes a short version of a file, and is difficult to reproduce without the original data. Any attempt at modifying the original data can then be detected, although the checksum itself has now to be trusted.
A signature is distinct from the sign of a number, + or -.
<?php
function foo(string $message): string {
// adapted from the PHP manual
// fetch private key from file and ready it
$pkeyid = openssl_pkey_get_private(file://src/openssl-0.9.6/php/sign/key.pem);
// compute signature
openssl_sign($message, $signature, $pkeyid);
// free the key from memory
openssl_free_key($pkeyid);
// This returns the signature of the message for 'php' user.
// It may be checked with the public key
return $signature;
}
?>
Related : Method Signature, Signature, Sign, Checksum
