What is CodeIgniter 4's Encryption class?

CodeIgniter 4's Encryption service provides authenticated symmetric encryption using OpenSSL (AES-256-CTR with HMAC-SHA512). Configure the key in app/Config/Encryption.php or generate one: php spark key:generate (stored in .env as encryption.key). Get the service: $encrypter = service("encrypter"). Encrypt: $encrypted = $encrypter->encrypt("sensitive data") — returns a base64-encoded string. Decrypt: $original = $encrypter->decrypt($encrypted). The encryption includes authentication (HMAC) — if the data is tampered with, decryption will fail. Use cases: encrypting sensitive data before storing in a database, securing cookies, or protecting config values. Do not use CI4's Encryption for passwords — use password_hash() and password_verify() instead.