otpd is part of a suite of software for authenticating users with
handheld OTP tokens. There are five components:
a. An authentication server. This is provided by you. Examples
are FreeRADIUS, unix daemons that use PAM, a krb5 KDC, etc.
b. A plugin for your auth server, that talks to otpd. You can
download plugins from the TRI-D Systems web site, or write
your own. Your authentication server software vendor might
also supply plugins for otpd.
* c. This software, otpd, which does the actual OTP validation.
d. A global state manager, gsmd, used in multi-server deployments
to coordinate and guarantee globally consistent state.
e. An optional LDAP directory server.