olemus
ühekordsete paroolide loomise süsteem, kus parool luuakse kasutaja tegelikust paroolist, lühikesest stringist ja allaloendurist;
on populaarne (Linux, OpenBSD, NetBSD, FreeBSD);
kasutamist piirab kogu seanssi turvavate krüptoprotokollide (SSH jt);
ja kaksikautentimise levik
S/KEY on firma Telcordia Technologies kaubamärk
= a one-time password generation system (a trademark of Telcordia Technologies) where a password is generated from the user's actual password, a short string and a countdown timer; is popular (Linux, OpenBSD, NetBSD, FreeBSD), but use is limited by cryptographic protocols that secure the entire session (SSH, e. a..) and two-factor authentication deployment

ülevaateid
https://en.wikipedia.org/wiki/S/KEY

http://www.ece.northwestern.edu/CSEL/skey/skey-brown.html

standard
https://tools.ietf.org/html/rfc1760