4 ms·
FTA: >The RFC8332 RSA SHA-2 signature algorithms rsa-sha2-256/512. These algorithms have the advantage of using the same key type as "ssh-rsa" but use the safe
by nemothekid 6y ago
FTA:
>The RFC8332 RSA SHA-2 signature algorithms rsa-sha2-256/512. These algorithms have the advantage of using the same key type as "ssh-rsa" but use the safe SHA-2 hash algorithms. These have been supported since OpenSSH 7.2 and are already used by default if the client and server support them.
It's unclear to me whether I'm using SHA1 or SHA2. Running ` ssh -oHostKeyAlgorithms=-ssh-rsa ` against one of my servers works, and I'm sure to have created my key before 2016 when OpenSSH 7.2 was released.
- RL_Quine 6y agoIf you run with -vv during auth there's some debug text to do with cryptography selection. In the case of github the response is: debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp256-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com,ssh-ed25519,ecdsa-sha2-nistp521,ecdsa-sha2-nistp384,ecdsa-sha2-nistp256,rsa-sha2-512,rsa-sha2-256,ssh-rsa,ssh-dss> Which suggests you'll be using rsa-sha2-256 with your client version, or absolutely nothing in the future if you're using one of the older releases such as on MacOS.
- _-___________-_ 6y agoIt doesn't matter when you created your key. This is protocol stuff. If you're using non-ancient OpenSSH, and the server is using non-ancient OpenSSH, and you haven't done anything silly like disable the sha2 signature algorithms, then you're already using them since they're preferred by default.
- georgyo 6y agoUnless you're using certificates, your rsa keys don't specify any hashing algo at all. The negotiating between the client and server decide the signature algo.