man ssh
and search for command= and from=from='1.2.3.4',command='/path/to/executable argument' ssh-rsa key name
,
. Host names are also supported.AllowUsersThis keyword can be followed by a list of user name patterns, separated by spaces. If specified, login is allowed only for user names that match one of the patterns. '*' and '?' can be used as wildcards in the patterns. Only user names are valid; a numerical user ID is not recognized. By default, login is allowed for all users. If the pattern takes the form USER@HOST then USER and HOST are separately checked, restricting logins to particular users from particular hosts.
dsa
with rsa
in the below..ssh/id_dsa.pub
file into .ssh/authorized_keys
in the user account on the destination.