[Haskell-cafe] Encrypting streamed data

David Turner dct25-561bs at mythic-beasts.com
Thu Jul 6 07:23:44 UTC 2017

Apologies, just seen the bit about wanting to pass the key in directly
rather than using the GPG keyring because there are no email addresses
attached to your various keys.

Maybe a silly question, but can you give them email addresses to identify
them in a GPG-compatible manner? They don't have to have associated
mailboxes so the addresses can be totally made-up.

If not, I'd probably start to look to something like openssl to do the
symmetric encryption and manage the keys for that separately. It looks
possible to build a streaming AES implementation using the nonstreaming
functions in `cryptonite`, but the usual recommendation is that its far too
risky to do any low-level crypto yourself so this seems like a bad idea.

On 6 Jul 2017 07:40, "David Turner" <dct25-561bs at mythic-beasts.com> wrote:

> Hi,
> I do not know of a library to do this, sorry. Note that the way public-key
> crypto works in a streaming fashion is typically to use the public-key bit
> only to encrypt a key for a symmetric cipher and then use the (much-faster)
> symmetric encryption for the actual data. The symmetric bit could well be
> something like AES256-CBC or AES256-CTR.
> This means that the format of the resulting data is a bit
> implementation-defined as it has to include the asymetrically-encrypted
> data first, followed by the stream of symmetrically-encrypted data. GnuPG
> includes quite a bit of metadata in its files that describes the algorithms
> used and delimits the pieces, so if you want the resulting files to be
> GnuPG-compatible you'll need to take this into account.
> If it were me, I'd probably just shell out to `gpg`. It's fast and
> low-risk.
> Hope that helps,
> David
> On 6 Jul 2017 05:59, "Ivan Lazar Miljenovic" <ivan.miljenovic at gmail.com>
> wrote:
> I have a use case for needing to use public key cryptography to
> encrypt a large amount of data in a streaming fashion (get it out of a
> DB, encrypt, put into an AWS S3 bucket).
> The command-line gpg tool seems to be able to encrypt/decrypt data
> from stdin to stdout in a streaming fashion, but in my attempts to use
> it it seems very file-based for things like the keys to use (whereas I
> would prefer to be able to pass the public key as an actual value
> rather than a file; if nothing else because this is for tools that
> don't have email addresses to use and base their keys on for
> addressing).
> Is there an existing library that can achieve this using
> conduit/pipes/whatever? cryptonite-conduit only covers hashing,
> hOpenPGP is poorly documented and I can't work out how to use it
> ("just follow the types" is difficult when Haddock docs don't link to
> the required types (seems to be because it uses the "import Module as
> X" trick for re-exporting everything but then everything from those
> modules isn't available).
> Can anyone recommend a solution?
> --
> Ivan Lazar Miljenovic
> Ivan.Miljenovic at gmail.com
> http://IvanMiljenovic.wordpress.com
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