Re: [MirageOS-devel] Compiling C components for mirage-xen

[Hannes Mehnert <hannes@xxxxxxxxxxx>]

On 01/14/2016 15:23, Arnaud Sahuguet wrote:
> Naive question: for low-level primitives like crypto that require speed,
> when do you/we prefer native implementation (in C at the libOS level) vs
> OCaml implementation?

I prefer nearly always OCaml code.  In our nqsb-tls paper
(https://nqsb.io/nqsbtls-usenix-security15.pdf) there's in Section 4.2 a
brief description of nocrypto.

It uses allocation-free (and (data-dependent) loop free) C code for the
AES and SHA1/SHA2 cores.  The C code gets a source and destination byte
vector, as well as a key, and does only the bit twiddling.  The cipher
modes (CBC/CTR/GCM/CCM) are implemented in OCaml.


hannes

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