cloak v0.7.0 Cloak.Ciphers.AES.CTR View Source

A Cloak.Cipher which encrypts values with the AES cipher in CTR (stream) mode. Internally relies on Erlang’s :crypto.stream_encrypt/2.

Link to this section Summary

Functions

can_decrypt?(ciphertext, opts)

Callback implementation for Cloak.Cipher.can_decrypt?2. Determines if a ciphertext can be decrypted with this cipher

decrypt(ciphertext, opts)

Callback implementation for Cloak.Cipher.decrypt/2. Decrypts a value encrypted with AES in CTR mode

encrypt(plaintext, opts)

Callback implementation for Cloak.Cipher.encrypt. Encrypts a value using AES in CTR mode

Link to this section Functions

can_decrypt?(ciphertext, opts)

Callback implementation for Cloak.Cipher.can_decrypt?2. Determines if a ciphertext can be decrypted with this cipher.

decrypt(ciphertext, opts)

Callback implementation for Cloak.Cipher.decrypt/2. Decrypts a value encrypted with AES in CTR mode.

Uses the key tag to find the correct key for decryption, and the IV included in the header to decrypt the body of the ciphertext.

Parameters

ciphertext - Binary ciphertext generated by encrypt/2.

Examples

iex> encrypt("Hello") |> decrypt
"Hello"

encrypt(plaintext, opts)

Callback implementation for Cloak.Cipher.encrypt. Encrypts a value using AES in CTR mode.

Generates a random IV for every encryption, and prepends the key tag and IV to the beginning of the ciphertext. The format can be diagrammed like this:

+----------------------------------+----------------------+
|              HEADER              |         BODY         |
+------------------+---------------+----------------------+
| Key Tag (1 byte) | IV (16 bytes) | Ciphertext (n bytes) |
+------------------+---------------+----------------------+
|                  |__________________________________
|                                                     |
+---------------+-----------------+-------------------+
| Type (1 byte) | Length (1 byte) | Key Tag (n bytes) |
+---------------+-----------------+-------------------+

The Key Tag component of the header breaks down into a Type, Length, and Value triplet for easy decoding.