Encryption Service


DO NOT use this or any other encryption library for user password storage! Passwords must be hashed instead, and you should do that via PHP’s own Password Hashing extension.

The Encryption Service provides two-way symmetric (secret key) data encryption. The encryption manager will instantiate and/or initialize an encryption handler to suit your parameters, explained below.

The handlers adapt our simple EncrypterInterface to use an appropriate PHP cryptographic extension or third party library. Such extensions may need to be explicitly enabled in your instance of PHP.

The following extensions are currently supported:


Support for the MCrypt extension has been dropped, as that has been deprecated as of PHP 7.2.

Using the Encryption Library

Like all services in CodeIgniter, it can be loaded via Config\Services:

$encrypter = \Config\Services::encrypter();

Default behavior

By default, the Encryption Library will use the OpenSSL handler, with the AES-256-CBC cipher, using your configured key and SHA512 HMAC authentication.

The key you provide is used for “keyed-hash message authentication” (HMAC), which derives two separate keys from your configured one: one for encryption and one for authentication. This is done via a technique called HMAC-based Key Derivation Function (HKDF).

Setting your encryption key

An encryption key is a piece of information that controls the cryptographic process and permits a plain-text string to be encrypted, and afterwards - decrypted. It is the secret “ingredient” in the whole process that allows you to be the only one who is able to decrypt data that you’ve decided to hide from the eyes of the public. After one key is used to encrypt data, that same key provides the only means to decrypt it, so not only must you chose one carefully, but you must not lose it or you will also lose access to the data.

It must be noted that to ensure maximum security, such a key should not only be as strong as possible, but also often changed. Such behavior however is rarely practical or possible to implement, and that is why CodeIgniter gives you the ability to configure a single key that is to be used (almost) every time.

It goes without saying that you should guard your key carefully. Should someone gain access to your key, the data will be easily decrypted. If your server is not totally under your control it’s impossible to ensure key security so you may want to think carefully before using it for anything that requires high security, like storing credit card numbers.

Your encryption key must be as long as the encryption algorithm in use allows. For AES-256, that’s 256 bits or 32 bytes (characters) long. You will find a table below that shows the supported key lengths of different ciphers.

The key should be as random as possible and it must not be a regular text string, nor the output of a hashing function, etc. In order to create a proper key, you can use the Encryption library’s createKey() method

// $key will be assigned a 32-byte (256-bit) random key
$key = Encryption::createKey(32);

The key can be either stored in your application/Config/Encryption.php, or you can design your own storage mechanism and pass the key dynamically when encrypting/decrypting.

To save your key to your application/Config/Encryption.php, open the file and set:

$key = 'YOUR KEY';

You’ll notice that the createKey() method outputs binary data, which is hard to deal with (i.e. a copy-paste may damage it), so you may use bin2hex(), hex2bin() or Base64-encoding to work with the key in a more friendly manner. For example:

// Get a hex-encoded representation of the key:
$encoded = bin2hex($encrypter->createKey(32));

// Put the same value in your config with hex2bin(),
// so that it is still passed as binary to the library:
$key = hex2bin(<your hex-encoded key>);

Encryption ciphers

A cipher is a combination of an algorithm, key length, and encryption mode. For instance, “AES-256-CBC” refers to the AES algorithm using a 256 bit key and cipher block chaining (CBC) mode.

Different encryption drivers support different sets of encryption algorithms and often implement them in different ways. Some algorithms expect specific key lengths, while others support variable length keys. Each algorithm usually supports several different encryption modes.

Here’s a list of common ciphers:

Algorithm name Key lengths (bits / bytes) Supported modes
AES-128 / Rijndael-128 128 / 16 CBC, CTR, CFB, CFB8, OFB, ECB
AES-192 192 / 24 CBC, CTR, CFB, CFB8, OFB, ECB
AES-256 256 / 32 CBC, CTR, CFB, CFB8, OFB, ECB
Blowfish 128-448 / 16-56 CBC, CFB, OFB, ECB
CAST5 / CAST-128 88-128 / 11-16 CBC, CFB, OFB, ECB
RC4 / ARCFour 40-2048 / 5-256 Stream
TripleDES 56 / 7, 112 / 14, 168 / 21 CBC, CFB, CFB8, OFB


Blowfish, CAST5 and RC4 support variable length keys, although in bit terms that only happens in 8-bit increments.

Even though CAST5 supports key lengths lower than 128 bits (16 bytes), in fact they will just be zero-padded to the maximum length, as specified in RFC 2144.

Encryption modes

Different modes of encryption have different characteristics and serve different purposes. Some are stronger than others, some are faster and some offer extra features. If you are unsure which to use, stick to the CBC mode - it is widely accepted as strong and secure for general purposes.

Mode name Additional info
CBC Cipher block chaining - a safe default choice
CFB Cipher feedback
CTR Counter mode
ECB Electronic codebook - ignores IV (not recommended).
OFB Output feedback
Stream Not actually a mode, it just says that a stream cipher is being used.

OpenSSL Notes

As noted above, the encryption drivers support different sets of encryption ciphers. The following examples are supported by OpenSSL:

Cipher name Key lengths (bits / bytes) Supported modes
AES-128 128 / 16 CBC, CTR, CFB, CFB8, OFB, ECB, XTS
AES-192 192 / 24 CBC, CTR, CFB, CFB8, OFB, ECB, XTS
AES-256 256 / 32 CBC, CTR, CFB, CFB8, OFB, ECB, XTS
Blowfish 128-448 / 16-56 CBC, CFB, OFB, ECB
Camellia-128 128 / 16 CBC, CFB, CFB8, OFB, ECB
Camellia-192 192 / 24 CBC, CFB, CFB8, OFB, ECB
Camellia-256 256 / 32 CBC, CFB, CFB8, OFB, ECB
CAST5 88-128 / 11-16 CBC, CFB, OFB, ECB
RC2 8-1024 / 1-128 CBC, CFB, OFB, ECB
RC4 40-2048 / 5-256 Stream
TripleDES 56 / 7, 112 / 14, 168 / 21 CBC, CFB, CFB8, OFB
Seed 128 / 16 CBC, CFB, OFB, ECB

Message Length

An encrypted string is usually longer than the original, plain-text string (depending on the cipher).

This is influenced by the cipher algorithm itself, the initialization vector (IV) prepended to the cipher-text and the HMAC authentication message that is also prepended. Furthermore, the encrypted message is also Base64-encoded so that it is safe for storage and transmission, regardless of a possible character set in use.

Keep this information in mind when selecting your data storage mechanism. Cookies, for example, can only hold 4K of information.

Configuring the library

The Encryption library is designed to use repeatedly the same driver, encryption cipher and key.

As noted in the “Default behavior” section above, this means using an auto-detected driver (OpenSSL has a higher priority), the AES-256 algorithm in CBC mode, and your $key value.

Encryption configuration settings are normally set in application/config/Encryption.php. Not all settings are supported by all of the drivers

Option Possible values (default in parentheses)
driver Preferred handler (OpenSSL)
cipher Cipher name (AES-256-CBC); see Encryption ciphers)
key Encryption key starter
digest Which HMAC digest algorithm to use (SHA512)
encoding The encoding to apply to encrypted results (base64)

You can over-ride any of those settings by passing your own Config object, or an associative array of parameters, or even just the driver name, to the Services:

$encrypter = \Config\Services::encrypter($params);

These will replace any same-named settings in Config\Encryption.

Supported HMAC authentication algorithms

For HMAC message authentication, the Encryption library supports usage of the SHA-2 family of algorithms:

Algorithm Raw length (bytes) Hex-encoded length (bytes)
sha512 64 128
sha384 48 96
sha256 32 64
sha224 28 56

Using the Encryption manager directly

Instead of, or in addition to, using the Services described at the beginning of this page, you can use the encryption manager directly, to create an Encrypter or to change the settings of the current one.

$encryption = new EncryptionEncryption(); $encrypter = $encryption->initialize($params);

For example, if you were to change the encryption algorithm and mode to AES-256 in CTR mode, this is what you should do:

$encryption = new \Encryption\Encryption();
$encrypter = $encryption->initialize([
        'cipher' => 'aes-256-ctr',
        'key' => '<a 32-character random string>'

Note that we only mentioned that you want to change the cipher, but we also included a key in the example. As previously noted, it is important that you choose a key with a proper size for the used algorithm.

If you want to change the driver, for instance switching between Sodium and OpenSSL, you could go through the Services:

// Switch to the Sodium driver
$encrypter= \Config\Services::encrypter(['driver' => 'Sodium']);;
// encrypt data using Sodium

// Switch back to the OpenSSL driver
$encrypter= \Config\Services::encrypter(['driver' => 'OpenSSL']);;
// now encrypt data using OpenSSL

Alternately, you could use the encryption manager directly:

$encryption = new EncryptionEncryption();

// Switch to the Sodium driver $encrypter= $encryption->initialize([‘driver’ => ‘Sodium’]);; // encrypt data using Sodium

// Switch back to the OpenSSL driver $encrypter= $encryption->initialize([‘driver’ => ‘OpenSSL’]);; // now encrypt data using OpenSSL

Note that it would be easier to save these separately, if both encrypters were to be needed as part of handling the same request.

$encryption = new EncryptionEncryption(); $encrypter1 = $encryption->initialize([‘driver’ => ‘Sodium’]);; $encrypter2 = $encryption->initialize([‘driver’ => ‘OpenSSL’]);;

Encrypting and decrypting data

Encrypting and decrypting data with the already configured library settings is simple - pass the appropriate string to the encrypt() and/or decrypt() methods:

$plain_text = 'This is a plain-text message!';
$ciphertext = $encrypter->encrypt($plaintext);

// Outputs: This is a plain-text message!
echo $encrypter->decrypt($ciphertext);

And that’s it! The Encryption library will do everything necessary for the whole process to be cryptographically secure out-of-the-box. You don’t need to worry about it.


Both methods will return FALSE in case of an error. While for encrypt() this can only mean incorrect configuration, you should always check the return value of decrypt() in production code.

Class Reference

static createKey($length)
  • $length (int) – Output length

A pseudo-random cryptographic key with the specified length, or FALSE on failure

Return type:


Creates a cryptographic key by fetching random data from the operating system’s sources (i.e. /dev/urandom).

  • $params (array) – Configuration parameters

CodeIgniter\Encryption\EncrypterInterface instance (for method chaining)

Return type:




Initializes (configures) the library to use different settings.


$encrypter = $encryption->initialize(['cipher' => '3des']);

Please refer to the Configuring the library section for detailed info.

  • $data (string) – Data to encrypt

Encrypted data or FALSE on failure

Return type:


Encrypts the input data and returns its ciphertext.


$ciphertext = $encrypter->encrypt('My secret message');
  • $data (string) – Data to decrypt

Decrypted data or FALSE on failure

Return type:




Decrypts the input data and returns it in plain-text.


echo $encrypter->decrypt($ciphertext);