  The SSH protocol is commonly used to access remote systems on the Internet,
as it provides an encrypted and authenticated channel for communication. If
upon establishing a new connection, the presented server key is unknown to the
client, the user is asked to verify the key fingerprint manually, which is
prone to errors and often blindly trusted. The SSH standard describes an
alternative to such manual key verification: using the Domain Name System (DNS)
to publish the server key information in SSHFP records.
  In this paper, we conduct a large-scale Internet study to measure the
prevalence of SSHFP records among DNS domain names. We scan the Tranco 1M list
and over 500 million names from the certificate transparency log over the
course of 26 days. The results show that in two studied populations, about 1 in
10,000 domains has SSHFP records, with more than half of them deployed without
using DNSSEC, drastically reducing security benefits.
