OpenSSH public key fingerprint

# syntax:
openssl pkey -in PATH/PRIVATE_RSA_KEY -pubout -outform DER | openssl md5 -c

# example:
$ openssl pkey -in ~/.ssh/id_rsa -pubout -outform DER | openssl md5 -c
MD5(stdin)= a6:26:23:d9:c1:d3:d5:e5:c0:38:ab:3c:c1:6a:3f:ea