[erlang-questions] SSL performance

Andreas Schultz aschultz@REDACTED
Wed Feb 11 17:11:42 CET 2015

----- On 11 Feb, 2015, at 16:59, Loïc Hoguin essen@REDACTED wrote:

> On 02/11/2015 04:29 PM, Andreas Schultz wrote:
>> The cause for this is not the cryptographic library, but Erlang's interface to
>> it.
>> Erlang's crypto application uses a non-optimized OpenSSL API to execute the AES
>> encryption, while enacl seems to uses an highly optimized version.
>> Normally when doing AES, you first have to schedule the key, creating an
>> encryption
>> context and then reuse that context for every block. Since the crypto
>> application
>> doesn't have stream_cipher versions of AES, it has to go through the key
>> scheduling
>> on every invocation (every block). Also, OpenSSL can use assembler optimized AES
>> functions on modern CPU's, but those are only available when OpenSSL's EVP
>> interfaces
>> are used. Erlang's crypto does not use those.
> I have seen some work around EVP in the past few months. Is this not
> what you are talking about?
> commit 425a34001fdd5de8396c5c9903f4f38a9d49a15c
> Author: Alex Wilson <alex@REDACTED>
> Date:   Thu Oct 9 21:39:29 2014 +1000
>     crypto: use EVP for AES-CBC
>     This enables the use of hardware acceleration for AES crypto
>     on newer Intel CPUs (AES-NI), among other platforms.

That is a good step in the right direction. Still, it has to recreate the
EVP crypto context for every invocation. There was a discussion about
keeping the EVP context between invocations and use the crypto 
stream_encrypt/decrypt instead. That would eliminate the overhead of the
context creation between calls.


> Cheers.
> --
> Loïc Hoguin
> http://ninenines.eu

Dipl. Inform.
Andreas Schultz

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