Crypto.Cipher.ChaChaPoly1305

A simple AEAD scheme using ChaCha20 and Poly1305. See RFC7539.

The State is not modified in place, so each function changing the State, returns a new State.

Authenticated Data need to be added before any call to encrypt or decrypt, and once all the data has been added, then finalizeAAD need to be called.

Once finalizeAAD has been called, no further appendAAD call should be make.

encrypt nonce key hdr inp =
   let st1        = ChaChaPoly1305.initialize key nonce
       st2        = ChaChaPoly1305.finalizeAAD $ ChaChaPoly1305.appendAAD hdr st1
       (out, st3) = ChaChaPoly1305.encrypt inp st2
       auth       = ChaChaPoly1305.finalize st3
    in out `B.append` Data.ByteArray.convert auth

Documentation

data State

A ChaChaPoly1305 State.

The state is immutable, and only new state can be created

data Nonce

Valid Nonce for ChaChaPoly1305.

It can be created with nonce8 or nonce12

Instances

ByteArrayAccess Nonce

nonce12 :: ByteArrayAccess iv => iv -> CryptoFailable Nonce

Nonce smart constructor 12 bytes IV, nonce constructor

nonce8

Arguments

:: ByteArrayAccess ba

=> ba

4 bytes constant

-> ba

8 bytes IV

-> CryptoFailable Nonce

8 bytes IV, nonce constructor

incrementNonce :: Nonce -> Nonce

Increment a nonce

initialize :: ByteArrayAccess key => key -> Nonce -> CryptoFailable State

Initialize a new ChaChaPoly1305 State

The key length need to be 256 bits, and the nonce procured using either nonce8 or nonce12

appendAAD :: ByteArrayAccess ba => ba -> State -> State

Append Authenticated Data to the State and return the new modified State.

Once no further call to this function need to be make, the user should call finalizeAAD

finalizeAAD :: State -> State

Finalize the Authenticated Data and return the finalized State

encrypt :: ByteArray ba => ba -> State -> (ba, State)

Encrypt a piece of data and returns the encrypted Data and the updated State.

decrypt :: ByteArray ba => ba -> State -> (ba, State)

Decrypt a piece of data and returns the decrypted Data and the updated State.

finalize :: State -> Auth

Generate an authentication tag from the State.