[Haskell-cafe] [Haskell] ANN: nonce package

Felipe Lessa felipe.lessa at gmail.com
Sun Jun 7 12:43:35 UTC 2015

On 07-06-2015 06:44, Geraldus wrote:
> вс, 7 июня 2015 г. в 13:26, Geraldus <heraldhoi at gmail.com
> <mailto:heraldhoi at gmail.com>>:
>     Hi, Felipe! Thank you for sharing!
>     The one question I have is there some good way to generate unique
>     nonces?

Nonces generated by the nonce package are always unique.  If not,
there's a huge bug, or your /dev/urandom is broken.

> Also it is good to make a new generator in function which
> produces a nonce? E.g.
> generateNonce :: forall (m :: * -> *). (MonadIO m, Functor m) => m Text
> generateNonce =
>   do g <- new
>      nonce128urlT g

You will not shoot yourself in the foot security-wise.  You are not able
to distinguish a sequence of nonces generated by

  replicateM n (new >>= nonce128urlT)


  new >>= replicateM n . nonce128urlT

However, 'new' is a _very_ expensive function.  Your generateNonce
function will have abysmal performance (and so will the first example
above).  Please avoid creating many generators.



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