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[ChaChaPoly1305] fix type error of example code

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The example code had a type mismatch.

    Couldn't match expected type ‘State’
                with actual type ‘CryptoFailable State’
    In the second argument of ‘appendAAD’, namely ‘st1’
    In the second argument of ‘($)’, namely ‘appendAAD hdr st1’

This is due to the following part:

    let st1 = ChaChaPoly1305.initialize key nonce
        st2 = ChaChaPoly1305.finalizeAAD $ ChaChaPoly1305.appendAAD hdr st1

`initialize` returns `CryptoFailable State`, not `State`.

This commit fixes the type mismatch, changes the return type of the
example function to `CryptoFailable ByteString`, and makes the code
to be immediately copy-and-paste-able.
This commit is contained in:
kinoru 2015-12-03 18:00:23 +00:00
parent 323327c9a5
commit 5a2809a0f8
1 changed files with 20 additions and 7 deletions
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27
Crypto/Cipher/ChaChaPoly1305.hs
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@ -5,7 +5,8 @@
-- Stability : stable
-- Portability : good
--
-- A simple AEAD scheme using ChaCha20 and Poly1305. See RFC7539.
-- A simple AEAD scheme using ChaCha20 and Poly1305. See
-- <https://tools.ietf.org/html/rfc7539 RFC 7539>.
--
-- The State is not modified in place, so each function changing the State,
-- returns a new State.
@ -15,12 +16,24 @@
--
-- 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
-- >import Data.ByteString.Char8 as B
-- >import Data.ByteArray
-- >import Crypto.Error
-- >import Crypto.Cipher.ChaChaPoly1305 as C
-- >
-- >encrypt
-- > :: ByteString -- nonce (12 random bytes)
-- > -> ByteString -- symmetric key
-- > -> ByteString -- optional associated data (won't be encrypted)
-- > -> ByteString -- input plaintext to be encrypted
-- > -> CryptoFailable ByteString -- ciphertext with a 128-bit tag attached
-- >encrypt nonce key header plaintext = do
-- > st1 <- C.nonce12 nonce >>= C.initialize key
-- > let
-- > st2 = C.finalizeAAD $ C.appendAAD header st1
-- > (out, st3) = C.encrypt plaintext st2
-- > auth = C.finalize st3
-- > return $ out `B.append` Data.ByteArray.convert auth
--
module Crypto.Cipher.ChaChaPoly1305
( State