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I have generated keys(public and private ) using SSH 2- RSA using putty key generator and configured public key in bitvise SSH server.

when i am trying to connect it with using key exchange : RSA based key exchange it working fine .

however when i am trying to connect it with using key exchange :Diffie-Hellman exchange its not working.

So ,key generation algorithm(RSA/DSA) should always same as key exchange algorithm (RSA/DSA) for communication?

can you anyone help me on this or redirect to links?

Thanks!

user525144
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    The key you generate with puttygen is used for _authentication_ (auth, specifically client auth) NOT keyexchange (kex). In SSH these steps can use the same or different algorithms, but DSA cannot do kex (while DH can only do kex and not auth). Did you try all three DH options? Do you have a packet-level log? That will show what the server offers (though less conveniently than OpenSSH `ssh -v` does). – dave_thompson_085 May 26 '19 at 02:20
  • Yes,kex is happening using DH only.below is the error message we are getting. Fatal: server sent disconnected message type 3(key exchange failed) "FlowSshTransport: no mutually supported host key algorithm.Local list: "ecdsa-sha2-nistp256".Remote list:"ssh-rsa,ssh-dss"." – user525144 May 27 '19 at 17:58
  • What version of putty? Your server is offering (only) ecdsa for _host_ key (server auth), and you need putty 0.68 up to support ecdsa (and ed25519) auth. Alternatively, change the server's key(s). – dave_thompson_085 May 28 '19 at 07:36
  • Thanks a lot :) – user525144 May 29 '19 at 21:12

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