Tutorial [Info] old Win98 putty 0.63 and armbian SSH

[guidol]

For "retro-reasons" I would like to SSH from my old Windows 98SE PC via putty 0.63 ( which is the last known to work under Windows98SE )
into armbian.

 

This did work fine until armbian bullseye dev with kernel 5.6.8, because here we get the "new" openssh-serve 8.2p1:
 

armbian bullseye kernel 5.6.8
openssh-server		1:8.2p1-4				arm64		secure shell (SSH) server, for secure access from remote machines

before bullseye we had with armbian buster and so on the "older" open-ssh-server <=7.9p1 (where we didnt got this problem)
 

armbian buster kernel 5.6.8
openssh-server		1:7.9p1-10+deb10u2		arm64		secure shell (SSH) server, for secure access from remote machines

 

with open-ssh-server 8.2p1 there was a "little" change:
 

https://www.openssh.com/releasenotes.html

OpenSSH 8.2/8.2p1 (2020-02-14)

Potentially-incompatible changes
================================

 * ssh(1), sshd(8): this release removes diffie-hellman-group14-sha1
   from the default key exchange proposal for both the client and
   server.

 

So the old putty 0.63 ( which is the last known to work under Windows 98 ) does produce the error-message:
couldn't agree a key exchange algorithm 

 

After comparing many many configs and commands (also ssh -Q kex) the solution "only" was 
 

nano /etc/ssh/sshd_config

# put at the end of /etc/sshd_config
KexAlgorithms +diffie-hellman-group14-sha1

/etc/init.d/ssh restart

Maybe this will help someone also using a older putty or other SSH-Client.
With a newer version of putty on newer Windows there was no problem with that