for OpenSSH
This adds a simple manual signature scheme to OpenSSH.
Signatures can be made and verified using ssh-keygen -Y sign|verify
Signatures embed the key used to make them. At verification time, this
is matched via principal name against an authorized_keys-like list
of allowed signers.
Mostly by Sebastian Kinne w/ some tweaks by me
ok markus@
OpenBSD-Commit-ID: 2ab568e7114c933346616392579d72be65a4b8fb
djm@openbsd.org