Extract Public Key and Fingerprint from Private Key

When managing SSH keys, you may need to extract the public key or obtain the fingerprint of a private key. Below are the commands to accomplish these tasks.

Get the Public Key

To extract the public key from a private key file, use the following command:

ssh-keygen -f keyname -y

Replace keyname with the path to your private key file.

Get the Fingerprint

SHA-1 Fingerprint

Convert the private key to DER format and compute the SHA-1 fingerprint:

openssl pkcs8 -in path_to_private_key -inform PEM -outform DER -topk8 -nocrypt | openssl sha1 -c

MD5 Fingerprint

Extract the public key in DER format and compute the MD5 fingerprint:

openssl rsa -in path_to_private_key -pubout -outform DER | openssl md5 -c

Summary

• Public Key: ssh-keygen -f keyname -y
• SHA-1 Fingerprint: openssl pkcs8 -in path_to_private_key -inform PEM -outform DER -topk8 -nocrypt | openssl sha1 -c
• MD5 Fingerprint: openssl rsa -in path_to_private_key -pubout -outform DER | openssl md5 -c

These commands help you extract the public key and obtain the fingerprints for verification purposes.