Simple FTP ServiceSFTPSSH keys

ssh-rsa client compatibility for SFTP

Fixing "no matching host key type found" and passwordless logins that still prompt for a password - the ssh-rsa deprecation, and when you need client config.

Updated August 27, 2026

DocEvent's SFTP servers use an RSA host key (see SSH host keys). Modern OpenSSH clients connect to our current servers without any special configuration - RSA keys are signed with the modern rsa-sha2 algorithms, which every current client accepts.

If you hit either of the errors below, you are most likely using an older client or library that only knows the legacy ssh-rsa (SHA-1) algorithm name, or an old server build. Both have the same workaround.

Error: "no matching host key type found. Their offer: ssh-rsa,ssh-dss"

Unable to negotiate with <host> port 22: no matching host key type found.
Their offer: ssh-rsa,ssh-dss

Your client refused to accept a legacy ssh-rsa host key signature. Allow it for DocEvent hosts only, in ~/.ssh/config:

Host *.docevent.io
    PubkeyAcceptedAlgorithms +ssh-rsa
    HostkeyAlgorithms +ssh-rsa

Passwordless login still asks for a password

You configured an authorized key but the server still prompts:

% sftp -i ~/.ssh/id_rsa serviceid/username@sfs-ap-southeast-2.docevent.io
serviceid/username@sfs-ap-southeast-2.docevent.io's password:

Run with -v and look for this line in the debug output:

debug1: send_pubkey_test: no mutual signature algorithm

That means your client would not sign with an algorithm the server accepts for your RSA key. The same ~/.ssh/config entry fixes it:

Host *.docevent.io
    PubkeyAcceptedAlgorithms +ssh-rsa

If the problem persists

Modern clients against the current servers should never need the above. If a fully updated client still fails, capture the output of sftp -vv ... and send it to support.