Safe Haskell	None
Language	Haskell2010

Crypto.Encrypt.Symmetric

Contents

Keys
Nonce
Encryption/decryption

Description

Symmetric authenticated encryption.

It is best to import this module qualified:

import qualified Crypto.Encrypt.Symmetric as Symmetric

encrypted = Symmetric.encrypt key nonce message
decrypted = Symmetric.decrypt key nonce encrypted

In NaCl this is know as a “Secretbox”. One way to think about it is to imagine that you are putting data into a box protected by a secret key. You “create” such a box using encrypt, store it somewhere (it is just a sequence of bytes), and when you need it in the future, you “open” it with decrypt using the same secret key.

Synopsis

type Key a = SizedByteArray CRYPTO_SECRETBOX_KEYBYTES a
toKey :: ByteArrayAccess ba => ba -> Maybe (Key ba)
type Nonce a = SizedByteArray CRYPTO_SECRETBOX_NONCEBYTES a
toNonce :: ByteArrayAccess ba => ba -> Maybe (Nonce ba)
encrypt :: (ByteArrayAccess keyBytes, ByteArrayAccess nonceBytes, ByteArrayAccess ptBytes, ByteArray ctBytes) => Key keyBytes -> Nonce nonceBytes -> ptBytes -> ctBytes
decrypt :: (ByteArrayAccess keyBytes, ByteArrayAccess nonceBytes, ByteArray ptBytes, ByteArrayAccess ctBytes) => Key keyBytes -> Nonce nonceBytes -> ctBytes -> Maybe ptBytes

Keys

type Key a = SizedByteArray CRYPTO_SECRETBOX_KEYBYTES a #

Encryption key that can be used for Secretbox.

This type is parametrised by the actual data type that contains bytes. This can be, for example, a ByteString, but, since this is a secret key, it is better to use ScrubbedBytes.

toKey :: ByteArrayAccess ba => ba -> Maybe (Key ba) #

Make a Key from an arbitrary byte array.

This function returns Just if and only if the byte array has the right length to be used as a key with a Secretbox.

Nonce

type Nonce a = SizedByteArray CRYPTO_SECRETBOX_NONCEBYTES a #

Nonce that can be used for Secretbox.

This type is parametrised by the actual data type that contains bytes. This can be, for example, a ByteString.

toNonce :: ByteArrayAccess ba => ba -> Maybe (Nonce ba) #

Make a Nonce from an arbitrary byte array.

This function returns Just if and only if the byte array has the right length to be used as a nonce with a Secretbox.

Encryption/decryption

encrypt Source #

Arguments

:: (ByteArrayAccess keyBytes, ByteArrayAccess nonceBytes, ByteArrayAccess ptBytes, ByteArray ctBytes)
=> Key keyBytes	Secret key
-> Nonce nonceBytes	Nonce
-> ptBytes	Plaintext message
-> ctBytes

Encrypt a message.

encrypted = Symmetric.encrypt key nonce message

key is the secret key used for encryption. See Crypto.Key for how to get one.
nonce is an extra noise that is required for security. See Crypto.Nonce for how to work with it.
message is the data you are encrypting.

This function adds authentication data, so if anyone modifies the cyphertext, open will refuse to decrypt it.

decrypt Source #

Arguments

:: (ByteArrayAccess keyBytes, ByteArrayAccess nonceBytes, ByteArray ptBytes, ByteArrayAccess ctBytes)
=> Key keyBytes	Secret key
-> Nonce nonceBytes	Nonce
-> ctBytes	Encrypted message (cyphertext)
-> Maybe ptBytes

Decrypt a message.

decrypted = Symmetric.decrypt key nonce encrypted

key and nonce are the same that were used for encryption.
encrypted is the output of create.

This function will return Nothing if the encrypted message was tampered with after it was encrypted.