PHP

DSA Signature Create and Verify

See more DSA Examples

Shows how to create a DSA (DSS) signature for the contents of a file. The first step is to create an SHA-1 hash of the file contents. The hash is signed using the Digital Signature Algorithm and the signature bytes are retrieved as a hex-encoded string.

The 2nd part of the example loads the signature and verifies it against the hash.

Chilkat2 PHP

<?php

use Chilkat2\Crypt2;
use Chilkat2\Dsa;

$success = false;

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

$crypt = new Crypt2();

$crypt->EncodingMode = 'hex';
$crypt->HashAlgorithm = 'sha-1';

// Return the SHA-1 hash of a file.  The file may be any size.
// The Chilkat Crypt component will stream the file when
// computing the hash, keeping the memory usage constant
// and reasonable.
// The 20-byte SHA-1 hash is returned as a hex-encoded string.
$hashStr = $crypt->HashFileENC('hamlet.xml');

$dsa = new Dsa();

// Load a DSA private key from a PEM file.  Chilkat DSA
// provides the ability to load and save DSA public and private
// keys from encrypted or non-encrypted PEM or DER.
// The LoadText method is for convenience only.  You may
// use any means to load the contents of a PEM file into
// a string.
$pemPrivateKey = $dsa->LoadText('dsa_priv.pem');
try {
    $dsa->FromPem($pemPrivateKey);
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

// You may optionally verify the key to ensure that it is a valid
// DSA key.
$success = $dsa->VerifyKey();
if (!$success) {
    echo $dsa->LastErrorText, "\n";
    exit;
}

// Load the hash to be signed into the DSA object:
try {
    $dsa->SetEncodedHash('hex', $hashStr);

    // Now that the DSA object contains both the private key and hash,
    // it is ready to create the signature:
    $dsa->SignHash();
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

// If SignHash is successful, the DSA object contains the
// signature.  It may be accessed as a hex or base64 encoded
// string.  (It is also possible to access directly in byte array form via
// the "Signature" property.)
$hexSig = $dsa->GetEncodedSignature('hex');
echo "Signature:\n";
echo $hexSig, "\n";

// -----------------------------------------------------------
// Step 2: Verify the DSA Signature
// -----------------------------------------------------------

$dsa2 = new Dsa();

// Load the DSA public key to be used for verification:
$pemPublicKey = $dsa2->LoadText('dsa_pub.pem');
try {
    $dsa2->FromPublicPem($pemPublicKey);

    // Load the hash to be verified against the signature.
    $dsa2->SetEncodedHash('hex', $hashStr);

    // Load the signature:
    $dsa2->SetEncodedSignature('hex', $hexSig);
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

// Verify:
try {
    $dsa2->Verify();
    echo "DSA Signature Verified!\n";
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
}