Improving performance

[silverdaz]

We replaced openssl chacha20 encryption/decryption with the ones from libsodium (via the pynacl bindings)

The test was:
Starting from a 1G file, named testfile with random data, we encrypt and decrypt n times, using intermediate staging files. We make sure that last file is the same as the original file (with diff).

The test script is:

#!/usr/bin/env bash
set -e

LIMIT=${1:-10}

unlink testfile.v1.1 &>/dev/null || true
ln -s testfile testfile.1

for (( i=1; i<=$LIMIT; i++ ))
do
    echo -n "o"
    crypt4gh encrypt --sk from.sec --recipient_pk to.pub < testfile.$i  > testfile.c4gh.$i
    echo -n "."
    crypt4gh decrypt --sk to.sec < testfile.c4gh.$i > testfile.$((i+1))
    unlink testfile.$i
    unlink testfile.c4gh.$i
done

echo "|"
diff testfile testfile.$i
unlink testfile.$i

and we time the execution, with 50 loops.

time	with openssl	with libsodium
real	5m57.990s	4m24.042s
user	3m53.821s	2m39.777s
sys	1m42.902s	1m35.706s

So it seems to bring an improvement of roughly 35%. Not bad.

We keep the cryptography dependency, because we use it to parse the ssh keys.