Convert Ed25519 to RSA fingerprint (or how to find SSH fingerprint)

Question

BizTalk sees thumbprint for an internal SFTP test as ssh-rsa 2048 33:88:f0:ff:63:78:a9:2b:3f:09:cb:05:81:db:59:86

WinSCP shows: ssh-ed25519 256 ff:2e:5e:33:7a:15:de:69:18:cf:82:ae:f0:4e:7b:d2 (when I click "Session", then "Server/Protocol Information")

Is it possible to convert one to the other? Is it possible to get the ssh-rsa thumbprint from WinSCP, PuTTY or some other tool?

Answer 1

WinSCP uses Ed25519 host key. It's a different key, than the RSA host key used by BizTalk. You cannot convert one to another.

WinSCP defaults to Ed25519 hostkey as that's preferred over RSA. You can only make WinSCP use RSA using raw session settings HostKey.

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Alternativelly, if you can connect with SSH terminal (e.g. PuTTY) to the server, use ssh-keygen to display a fingerprint of the RSA host key:

ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key

(this assumes common *nix server with OpenSSH)

Note that this makes sense only, if you had verified the host key, that the SSH terminal uses, upfront.

See WinSCP FAQ on Where do I get SSH host key fingerprint to authorize the server?, which covers all this.