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--- doc:appunti:linux:sa:ssh_config [2022/02/15 18:09] – [No matching key exchange method] niccolo
+++ doc:appunti:linux:sa:ssh_config [2022/02/28 18:21] – [No mutual signature algorithm] niccolo
@@ Line 20: / Line 20: @@
 This will force the use of **diffie-hellman-group1-sha1** key exchange method, which is considered less secure nowday.
+===== "no matching host key type" and "no mutual signature algorithm" =====
+Problem connecting from a modern (2022-02) **Termux** environment to an old **Debian 6 Squeeze**:
+<code>
+Unable to negotiate with 192.168.0.250 port 22:
+  no matching host key type found. Their offer: ssh-rsa,ssh-dss
+</code>
+So the first option to add is **HostKeyAlgorithms**, but there is another and more subtle problem, because no error message is printer unless you add the **-v** option (for verbose),
+<code>
+debug1: send_pubkey_test: no mutual signature algorithm
+debug1: No more authentication methods to try.
+root@192.168.0.250: Permission denied (publickey).
+</code>
+So also the **PubkeyAcceptedKeyTypes** is required:
+<code>
+ssh -o HostKeyAlgorithms=+ssh-rsa -o PubkeyAcceptedKeyTypes=+ssh-rsa root@192.168.0.250
+</code>