.SH HOST URIs
Host OpenPGP keys have associated user IDs that use the ssh URI
-specification for the host, ie. "ssh://host.full.domain".
+specification for the host, ie. "ssh://host.full.domain[:port]".
.SH KEY ACCEPTABILITY
The key must have the "authentication" ("a") usage flag set.
.TP
.B validity
-The key must be "fully" valid, and must not be expired or revoked.
+The key must be "fully" valid (ie. signed by a trusted certifier), and
+must not be expired or revoked.
.SH FILES
system crontab, so that user keys are kept up-to-date, and key
revokations and expirations can be processed in a timely manor.
+.SH KEY ACCEPTABILITY
+
+GPG keys are considered acceptable if the following criteria are met:
+.TP
+.B capability
+The key must have the "authentication" ("a") usage flag set.
+.TP
+.B validity
+The key must be "fully" valid (ie. signed by a trusted certifier), and
+must not be expired or revoked.
+
.SH FILES
.TP