SSH Key Fingerprint
Show the SHA256 and MD5 fingerprints, key type and size of SSH public keys from id_ed25519.pub, authorized_keys or known_hosts.
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Input
Show SSH key fingerprints
Output
0 keys
| Type | SHA-256 | MD5 | Comment |
|---|
SHA256: followed by unpadded base64 is what ssh-keygen -lf prints and what ssh shows when it first meets a host; the MD5 form is what older OpenSSH (before 6.8) and some cloud consoles still show. Compare the fingerprint ssh asks you to accept against one obtained another way, never by reading it from the same connection.
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About this tool
Method, assumptions, practical next steps, and limits.
Verifying a host
When ssh connects to a new server it shows the host key's SHA256 fingerprint and asks you to confirm. Comparing it against the fingerprint obtained another way (from the provider's console output, or ssh-keygen -lf /etc/ssh/ssh_host_ed25519_key.pub run on the server) is what stops a man-in-the-middle on first connection. The ssh-keygen manual documents the formats.
Auditing authorized_keys
Pasting an authorized_keys file lists every key that can log in, with its fingerprint and comment, which makes it easy to spot a key that should have been removed when someone left.