If SSH warns you that the host key has changed

• Overview
• Possible causes
• Verify that the change is legitimate

Overview

When you connect to a host for the first time, SSH asks if you want to accept the server's encryption key. If you choose to accept and save it, SSH stores the key in its list of host keys. If SSH ever receives a key from this host that doesn't match the saved key, it will alert you that the host's key has changed.

Possible causes

Another more benign reason may be that the host has updated its SSH software, in which case you will have to receive a new host key.

Verify that the change is legitimate

Before downloading and accepting a new key, you should first verify with a trusted source (such as the host's system administrator) that the legitimate host has had its SSH software upgraded or changed. If the legitimate host confirms the change, delete the old host key and accept the new host key.