Explicit computation and taking apart

This module provides two class of unsafe functions:

1. Functions to compute AEAD tokens with explicit key and Nounce
2. Functions to take apart an AEAD token into their constituents, namely the nounce used, the cipher text, and the authentication tag.

The former is to help interface with other libraries where as the latter allows us to serialise AEAD tokens.

WARNING: The security of the interface is compromised if

1. The key gets revealed to the attacker or
2. If the same key/nounce pair is used to lock two different messages.
3. Taking apart the AEAD token may compromises type safety.

Nounces need not be private and may be exposed to the attacker. In fact, in the safe version of these locking function, we pick the nounce at random (using the csprg) and pack it into the AEAD token.

For specific algorithms, the unsafe version is also available

• Raaz.AuthEncrypt.Unsafe.ChaCha20Poly1305
• Raaz.AuthEncrypt.Unsafe.XChaCha20Poly1305

The former has a smaller nounce (96-bits) than the latter (192-bits) and hence there is a slight risk in using it with randomly generated nounces. It is however, slightly faster and is safe to use when there is frequent key resets as in the case of network protocols. As with other cases we recommend the use of the default interface instead of the specific one when ever possible.