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Two-way encryption of messages for secure plain text transmission.

When messages are passed between two systems over a public network, encryption tools are needed to protect the content in transit. Encrypting and decrypting messages correctly can be fiddly and error-prone, so this library keeps the process small and explicit through the PlainTextMessage, EncryptedMessage, CipherText, Key, and InitVector abstractions.

Pass your secret message to the PlainTextMessage constructor, then call encrypt() with a shared Key to produce a CipherText. The encrypted payload is represented by the cipher text itself plus the IV returned by getIv(). Those values can then be passed to the receiver by any communication mechanism, with only the holder of the same shared key able to decrypt the original message.

On the receiving side, construct an EncryptedMessage with the incoming cipher text and IV, then call decrypt() with the same Key to recover the original plain text.

The CipherText class also provides a getUri() method for creating a pre-encoded URI. A URI containing cipher and iv query string parameters can then be passed to EncryptedUri and decrypted back into a PlainTextMessage.

A very small example

use GT\Cipher\Key;
use GT\Cipher\Message\EncryptedMessage;
use GT\Cipher\Message\PlainTextMessage;

$key = new Key();
$plainText = new PlainTextMessage("Hello, PHP.GT!");
$cipherText = $plainText->encrypt($key);

$received = new EncryptedMessage((string)$cipherText, $plainText->getIv());
echo $received->decrypt($key);

The message starts as plain text, is encrypted with a shared key, then reconstructed and decrypted on the receiving side using the same key and IV.

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To see where each class fits before wiring anything up, continue to Overview.