Fixing “Putty Server’s Host Key Did Not Match The Signature Supplied”

Hello Dev, have you ever encountered an error message saying “Putty Server’s Host Key Did Not Match The Signature Supplied”? This can be frustrating, especially if you’re trying to connect to a remote server for work or personal use. Don’t worry, we’ve got you covered. In this article, we’ll discuss the causes of this error and how to fix it step-by-step.

What is the “Putty Server’s Host Key Did Not Match The Signature Supplied” error?

The “Putty Server’s Host Key Did Not Match The Signature Supplied” error occurs when you’re trying to connect to a remote server using Putty, but the server’s host key doesn’t match the signature that’s stored in your local cache. This typically happens when the remote server has been reinstalled or has undergone a major update. The error message usually looks like this:

Putty Security Alert

Hostname	example.com
Type of key	SSH-2 RSA
Fingerprint	ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff
Host key not found in cache
Do you want to accept the key?	Y/N

If you choose to accept the key, Putty will store it in your local cache so that you won’t see this error message in the future. However, if you’re seeing this error message repeatedly, it’s likely because the server has a new host key that doesn’t match the old one in your cache.

What causes the “Putty Server’s Host Key Did Not Match The Signature Supplied” error?

There are several reasons why you might encounter this error message:

The remote server’s host key has changed.

If the remote server has been reinstalled or has undergone a major update, it’s possible that its host key has changed. This can cause the error message to appear, as the new host key won’t match the old one stored in your cache.

Your local cache is outdated or corrupted.

If your local cache is outdated or corrupted, it won’t be able to authenticate the server’s host key properly. This can cause the error message to appear, even if the server’s host key hasn’t changed.

How to fix the “Putty Server’s Host Key Did Not Match The Signature Supplied” error

Now that we’ve identified the causes of the error message, let’s go over the steps to fix it:

Step 1: Verify the host key

The first step is to verify that the host key presented by the server is correct. You can do this by comparing the fingerprint displayed in the error message with the actual fingerprint of the server’s host key. You can obtain the actual fingerprint by contacting the server administrator or by accessing the server through another method, such as a web console.

Step 2: Update your local cache

If the host key presented by the server is correct, you’ll need to update your local cache in order to authenticate it properly. To do this, follow these steps:

1. Click the “Yes” button in the error message to accept the new host key.
2. Open Putty and navigate to the “SSH” category in the left-hand menu.
3. Select “Auth” and click “Browse” next to the “Private key file for authentication” field.
4. Browse to the location of your private key file and click “Open”.
5. Click “Open” to connect to the server. Putty will automatically update your local cache with the new host key.

Step 3: Clear your local cache

If updating your local cache doesn’t work, it’s possible that your cache is corrupted or outdated. In this case, you’ll need to clear your local cache and start fresh. To do this, follow these steps:

1. Open Putty and navigate to the “SSH” category in the left-hand menu.
2. Select “Auth” and click “Browse” next to the “Private key file for authentication” field.
3. Browse to the location of your private key file and click “Open”.
4. Click “Session” in the left-hand menu and enter the hostname and port of the remote server you’re trying to connect to.
5. Click “Open” to connect to the server. Putty will prompt you to accept the new host key.

Step 4: Contact the server administrator

If none of the above steps work, it’s possible that the server administrator has made changes to the server’s security settings that are causing the error message to appear. In this case, you’ll need to contact the server administrator for further assistance.

FAQs

Q: Can I ignore the “Putty Server’s Host Key Did Not Match The Signature Supplied” error message?

A: While it’s possible to ignore the error message by clicking “Yes” to accept the new host key, it’s not recommended. This is because the error message indicates that the server’s security settings have changed, which could potentially be a sign of a security breach. By verifying and updating your local cache, you can ensure that your connection to the server is secure and authenticated.

Q: Can I fix the “Putty Server’s Host Key Did Not Match The Signature Supplied” error permanently?

A: Yes, you can fix the error permanently by accepting the new host key and updating your local cache. However, it’s important to note that the server’s host key could potentially change again in the future, which could cause the error message to reappear. Make sure to keep your local cache updated and verify the host key whenever you encounter this error message.

Q: Can I use a different SSH client instead of Putty?

A: Yes, there are many different SSH clients available, such as OpenSSH, SecureCRT, and Bitvise. However, the steps to fix the “Putty Server’s Host Key Did Not Match The Signature Supplied” error may vary depending on the SSH client you’re using.

Conclusion

The “Putty Server’s Host Key Did Not Match The Signature Supplied” error can be frustrating, but it’s important to take the necessary steps to ensure that your connection to the remote server is secure and authenticated. By verifying the host key and updating your local cache, you can fix the error and connect to the server without any issues. If you’re still having trouble, don’t hesitate to contact the server administrator for further assistance.