libssh2_knownhost_writeline(3) on Linux
The text 32c23d5b4393, as Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie), Debian 7 (Wheezy), Debian 6.0 (Squeeze) shipped it.
convert a known host to a line for storage