How Can I Implement Simple Two-Way Encryption in PHP?

Simplest Two-Way Encryption Using PHP

While RC4 is a common encryption method in PHP, it lacks native support and introduces unnecessary code complexity. For simplified and portable encryption, consider the following approaches:

Using OpenSSL with CTR Mode:

If PHP 5.4 or later is available, OpenSSL's openssl_encrypt() and openssl_decrypt() provide a more secure and efficient encryption method:

// Choose a strong cipher from this list: https://www.openssl.org/docs/man1.1.1/man3/EVP_CIPHER_CTX_new.html
$cipher = 'aes-256-ctr';

Using libsodium Compat:

Libsodium offers a robust cryptography library with authenticated encryption capabilities. Its PHP extension, libsodium-compat, provides a convenient interface:

// Install libsodium-compat: composer require box/codeigniter4-libsodium-compat
// Create a new instance of the crypto class
$crypto = new Crypto();

Building a Custom Encryption System:

If you prefer to roll your own encryption mechanism, consider the following:

UnsafeCryptography:

This class provides basic encryption functionality without authentication:

class UnsafeCryptography
{
    // Your encryption code...
}

SaferCryptography:

This class extends UnsafeCryptography and adds authentication to protect against ciphertext tampering:

class SaferCryptography extends UnsafeCryptography
{
    // Your authentication code...
}

Remember:

• Never encrypt passwords directly; use a password hashing algorithm instead.
• Unauthenticated encryption remains vulnerable to malicious tampering.
• Carefully consider the security implications and consult cryptographers for guidance before using these custom encryption methods.

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