Securing OpenSSH

You can set up SSH to prefer Elliptic Curve cryptography over RSA, and use modern key exchange algorithms without exposing yourself to Logjam-style attacks. It’s also good to get rid of SHA1 and MD5.

A good resource is the OpenSSH Guidelines page on the Mozilla wiki. You can basically copy the config.

Caveat: I found out that the version of Paramiko in Debian Jessie does not support SHA2 hashes or ECC in the key exchange. Paramiko was used in my case by duplicity. If you upgrade to the most recent version from pypi you can use diffie-hellman-exchange-group-sha256.

Thom Wiggers
PhD candidate at Radboud University

My research interests include (post-quantum) cryptography and protocols