How can we do PGP encryption/decryption using RSA in Php?

Question

I have installed GnuPG library and used below code for encryption and decryption:

$public_key = '/path/0xC6235F66-pub.asc';
$private_key = '/path/0xC6235F66-sec.asc';


function encryptText($public_key, $text)
{
    // Set GnuPG homedir to /tmp
    putenv("GNUPGHOME=/tmp");

    $public_key = file_get_contents($public_key); 

    // Create new GnuPG instance
    $gpg = new gnupg();
    // Import given public key
    $key = $gpg->import($public_key);
    // Add imported key for encryption
    $gpg->addencryptkey($key['fingerprint']);
    // Encrypt the secret to a PGP message
    $enc = $gpg->encrypt($text);
    // Clear the encryption key
    $gpg->clearencryptkeys();
    // Return  the PGP message

    return $enc;
}


function decryptText($private_key, $encryptedText)
{
    // Set GnuPG homedir to /tmp
    putenv("GNUPGHOME=/tmp");

    $private_key = file_get_contents($private_key); 

    // Create new GnuPG instance
    $gpg = new gnupg();
    // Import given public key
    $key = $gpg->import($private_key);
    // Add imported key for encryption
    $gpg->addencryptkey($key['fingerprint']);
    // Encrypt the secret to a PGP message
    $decText = $gpg->decrypt($encryptedText);
    // Clear the encryption key
    $gpg->clearencryptkeys();
    // Return  the PGP message

    return $decText;
}


$encrypted = encryptText($public_key, $input = 'just an example');
echo 'Encrypted text: '.$encrypted;

$decrypted = decryptText($private_key, $encrypted);
echo 'Decrypted text: '.$decrypted;

echo 'Match: ';
var_dump($input === $decrypted);

Using the above encryptText() function I got the encrypted text but unable to decrypt the same with function decryptText(). As i know, PGP encryption using rsa works with private & public key. I have both the keys in place and using public key for encryption which is giving some encrypted string output but unable to decrypt the encrypted string.

Please help here.

Answer 1

You should not hard-code the fingerprint. You should also use the private key to decrypt.

function encryptText($public_key, $data)
{
    $gpg = gnupg_init();
    ['fingerprint' => $fingerprint] = gnupg_import($gpg, $public_key);
    gnupg_addencryptkey($gpg, $fingerprint);

    return base64_encode(gnupg_encrypt($gpg, $data));
}

function decryptText($private_key, $data)
{
    $gpg = gnupg_init();
    ['fingerprint' => $fingerprint] = gnupg_import($gpg, $private_key);
    gnupg_addencryptkey($gpg, $fingerprint);

    return gnupg_decrypt($gpg, base64_decode($data));
}

print $encrypted = encryptText($public_key, $input = 'just an example');
print $decrypted = decryptText($private_key, $encrypted);
var_dump($input === $decrypted);