(PHP Extension) RSA Encrypt and Decrypt Credit Card Numbers

PHP Extension sample code to RSA public-key encrypt and decrypt credit card numbers. The RSA key is loaded from an unencrypted PKCS8 file. Chilkat provides many ways of setting the key -- loading from both encrypted and unencrypted PEM, PKCS8, DER, PVK, etc. Keys may be loaded from files or in-memory representations. (The RSA component also provides the ability to generate RSA keys.)

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<?php

// The version number (9_5_0) should match version of the Chilkat extension used, omitting the micro-version number.
// For example, if using Chilkat v9.5.0.48, then include as shown here:
include("chilkat_9_5_0.php");

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

$rsa = new CkRsa();

$key = new CkPrivateKey();

// Load an RSA private key from a file:
$success = $key->LoadAnyFormatFile('rsaPrivateKey.key','');
if ($success != true) {
    print $key->lastErrorText() . "\n";
    exit;
}

// Get the key as XML:

$keyXml = $key->getXml();

// We'll encrypt with the public key and decrypt with the private
// key.  (It's also possible to do the reverse.)
// Note: An RSA private key is composed of different parts internally: modulus, exponent, P, Q, etc.
// An RSA public-key is a sub-set of the private key.
// Therefore, when you have a private key, you really have
// both public and private keys.
$success = $rsa->ImportPublicKey($keyXml);
if ($success != true) {
    print $rsa->lastErrorText() . "\n";
    exit;
}

// Encrypt a VISA credit card number:
// 1234-5678-0000-9999
$ccNumber = '1234567800009999';

$usePrivateKey = false;
$rsa->put_EncodingMode('base64');
$encryptedStr = $rsa->encryptStringENC($ccNumber,$usePrivateKey);
print 'Encrypted:' . "\n";
print $encryptedStr . "\n";

// Now decrypt:
$rsaDecryptor = new CkRsa();

$rsaDecryptor->put_EncodingMode('base64');
$success = $rsaDecryptor->ImportPrivateKey($keyXml);

$usePrivateKey = true;
$decryptedStr = $rsaDecryptor->decryptStringENC($encryptedStr,$usePrivateKey);

print 'Decrypted:' . "\n";
print $decryptedStr . "\n";

// Important: RSA encryption should only be used to encrypt small amounts of data.
// It is typically used for encrypting symmetric encryption
// keys such that a symmetric encryption algorithm, such as 
// AES is then used to encrypt/decrypt bulk data

?>