Crypto.Scrypt
Contents
Description
Scrypt is a sequential memory-hard key derivation function. This module
provides low-level bindings to the scrypt key derivation function as
well as a higher-level password-storage API. It is based on a fast C
implementation of scrypt, written by Colin Percival. For further
information see http://www.tarsnap.com/scrypt.html.
- data ScryptParams
- scryptParams :: Integer -> Integer -> Integer -> Maybe ScryptParams
- defaultParams :: ScryptParams
- newtype EncryptedPass = EncryptedPass {}
- encryptPass :: ScryptParams -> Pass -> IO EncryptedPass
- encryptPass' :: Pass -> IO EncryptedPass
- verifyPass :: ScryptParams -> Pass -> EncryptedPass -> (Bool, Maybe EncryptedPass)
- verifyPass' :: Pass -> EncryptedPass -> Bool
- newtype Pass = Pass {
- unPass :: ByteString
- newtype Salt = Salt {
- unSalt :: ByteString
- newtype PassHash = PassHash {
- unHash :: ByteString
- scrypt :: ScryptParams -> Salt -> Pass -> PassHash
- scrypt' :: Salt -> Pass -> PassHash
Parameters to the scrypt function
Scrypt takes three tuning parameters: N, r and p. They affect running
time and memory usage:
Memory usage is approximately 128*r*N bytes. Note that the
scryptParams function takes log_2(N) as a parameter. As an example,
the defaultParams
log_2(N) = 14, r = 8 and p = 1
lead to scrypt using 128 * 8 * 2^14 = 16M bytes of memory.
Running time is proportional to all of N, r and p. Since it's
influence on memory usage is small, p can be used to independently tune
the running time.
data ScryptParams Source
Encapsulates the three tuning parameters to the scrypt function: N,
r and p (see above).
Instances
Arguments
| :: Integer |
|
| -> Integer | The parameter |
| -> Integer | The parameter |
| -> Maybe ScryptParams | Returns |
Constructor function for the ScryptParams data type
defaultParams :: ScryptParamsSource
Default parameters as recommended in the scrypt paper:
N = 2^14, r = 8, p = 1
Equivalent to fromJust (scryptParams 14 8 1)
Password Storage
To allow storing encrypted passwords conveniently in a single database
column, the password storage API provides the data type EncryptedPass. It
combines a Pass as well as the Salt and ScryptParams used to compute
it into a single ByteString, separated by pipe ("|") characters. The
Salt and PassHash are base64-encoded. Storing the ScryptParams with
the password allows to gradually strengthen password encryption in case of
changing security requirements.
A usage example is given below, showing encryption, verification and
changing ScryptParams:
>>> encrypted <- encryptPass defaultParams (Pass "secret")
>>> print encrypted
EncryptedPass {unEncryptedPass = "14|8|1|Wn5x[SNIP]nM=|Zl+p[SNIP]g=="}
>>> print $ verifyPass defaultParams (Pass "secret") encrypted
(True,Nothing)
>>> print $ verifyPass defaultParams (Pass "wrong") encrypted
(False,Nothing)
>>> let newParams = fromJust $ scryptParams 16 8 1
>>> print $ verifyPass newParams (Pass "secret") encrypted
(True,Just (EncryptedPass {unEncryptedPass = "16|8|1|Wn5x[SNIP]nM=|ZmWw[SNIP]Q=="}))
encryptPass :: ScryptParams -> Pass -> IO EncryptedPassSource
Encrypt the password with the given parameters and a random 32-byte salt.
The salt is read from /dev/urandom on Unix systems or CryptoAPI on
Windows.
encryptPass' :: Pass -> IO EncryptedPassSource
Equivalent to encryptPass defaultParams.
Arguments
| :: ScryptParams | Parameters to use for updating the |
| -> Pass | The candidate |
| -> EncryptedPass | The |
| -> (Bool, Maybe EncryptedPass) | Returns a pair of
|
Verify a Pass against an EncryptedPass. The function also takes
ScryptParams meeting your current security requirements. In case the
EncryptedPass was generated with different parameters, the function
returns an updated EncryptedPass, generated with the given
ScryptParams. The Salt is kept from the given EncryptedPass.
verifyPass' :: Pass -> EncryptedPass -> BoolSource
Check the Pass against the EncryptedPass, using the ScryptParams
encapsulated in the EncryptedPass.
Low-level bindings to the scrypt key derivation function
Bindings to a fast C implementation of scrypt. For password storage,
consider using the more convenient higher-level API above.
Constructors
| PassHash | |
Fields
| |