casper

An interface to the ChaCha20-Poly1305 symmetric cipher via Erlang and Node libraries. The “with” variants allow you to add additional authenticated data AAD which is required for encryption and decryption.

Types

SecretKey

opaque </>

A 32 byte secret key. It is encoded as a thunk to avoid leaking the key in logs.

pub opaque type SecretKey

Values

decrypt

</>

pub fn decrypt(
  message input: BitArray,
  key secret: SecretKey,
) -> Result(BitArray, Nil)

Given a BitArray (the output from encrypt) and a SecretKey attempt to decrypt the message.

This method will return Error(Nil) if it is unable to decrypt the input. This might happen if you don’t call encrypt first.

The javascript target uses Node’s crypto library and will not work on the web. The bun and deno runtimes are not supported.

decrypt_with

</>

pub fn decrypt_with(
  message input: BitArray,
  associated_data associated_data: BitArray,
  key secret: SecretKey,
) -> Result(BitArray, Nil)

See decrypt. This method uses additional authenticated data to decrypt the message.

encrypt

</>

pub fn encrypt(
  message input: BitArray,
  key secret: SecretKey,
) -> BitArray

Given a BitArray message and a SecretKey encrypt the message via ChaCha20-Poly1305. The output BitArray is encoded especially for this cipher.

The javascript target uses Node’s crypto library and will not work on the web. Currently bun and deno runtimes are unsupported.

encrypt_with

</>

pub fn encrypt_with(
  message input: BitArray,
  associated_data associated_data: BitArray,
  key secret: SecretKey,
) -> BitArray

See encrypt. This method adds additional authenticated data to the message for encryption.

from_bytes

</>

pub fn from_bytes(input: BitArray) -> Result(SecretKey, Nil)

Attempt to convert a BitArray into a SecretKey. This is useful when you want to read an encryption key from your environment. For example, you could store a base64 encoded secret as an environment variable. In the Erlang shell, base64:encode(crypto:strong_rand_bytes(32)).

If you don’t provide 32 bytes it will return Error(Nil).

new_key

</>

pub fn new_key() -> SecretKey

Generate a new SecretKey. This is only useful if you aren’t persisting the results of ciphers. See from_bytes for more details.