Unable to exchange encryption keys

Hello,

I am using git for windows with Matlab and SSH authentification. Everything worked fine, but suddenly it stopped working. I get the error message:

"Unable to connect to the remote git@gitlab ... .

Unable to authenticate using SSH to .

Caused by:

failed to start SSH session: Unable to exchange encryption keys"

I already tried to renew the keys, I tried ed25519 keys as well as RSA keys. The keys are added to the Git account. I updated Git for Windows. In Matlab, the getenv('USERPROFILE') shows the correct path, I also added the keys in Matlab using

git.PrivateKeyFile.PersonalValue = "path\.ssh\id_rsa"

git.PublicKeyFile.PersonalValue = "path\.ssh\id_rsa.pub"

Unfortunately, nothing helped and I still get this error message. What can be the issue?

Answer 1

[Hassaan]

1. Outdated SSH Software: Ensure that you're running the latest version of the SSH software on your system. Older versions might not support the newer encryption algorithms required by the server.
2. Server Configuration: The issue might be related to the server-side configuration. Some servers might have updated their security policies to disallow certain encryption algorithms or key types. You can verify this by checking the server's SSH configuration and its supported encryption algorithms.
3. Client Configuration: On the client side, ensure that your SSH configuration is set up correctly and that it supports the encryption methods accepted by the server.
4. Corrupt or Unsupported Keys: It's possible that the keys are corrupt or not supported. You mentioned trying both RSA and ed25519 keys; make sure they are generated correctly and are not corrupted. RSA keys should generally be at least 2048 bits in length due to newer security standards.
5. Firewall or Network Issues or Anitivirus: Sometimes, network or firewall or antivirus settings can interfere with SSH key exchange. Ensure that there are no such barriers affecting the communication between your client and the server.
6. Libraries and Dependencies: If you are using a library or tool that depends on underlying SSH libraries (like libgit2), there could be issues with the library itself that might require an update or a workaround. For instance, some users have found that using the command line instead of a GUI can circumvent issues if the GUI application is not properly handling SSH key exchanges.

If none of the above solutions work, you might want to consider reaching out to the support for the service you're trying to connect.

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Answer 2

[Stephan Freitag]

After updating MATLAB, I now get the error message: "Failed to retrieve list of SSH authentification methods: Failed getting response".

[Stephan Freitag]

Update: After updating Matlab again, creating a new rsa key again (without password), it suddendly works again now. I don't really know, what the issue was.