Th Scr Shll Prtcl (SSH) s cryptgrphc ntwrk prtcl fr prtng ntwrk srvcs scrly vr n nscrd ntwrk. ts mst ntbl pplctns r rmt lgn nd cmmnd-ln xctn.
SSH ws dsgnd fr nx-lk prtng systms s rplcmnt fr Tlnt nd nscrd rmt nx shll prtcls, sch s th Brkly Rmt Shll (rsh) nd th rltd rlgn nd rxc prtcls, whch ll s nscr, plntxt mthds f thntctn, lk psswrds.
Snc mchnsms lk Tlnt nd Rmt Shll r dsgnd t ccss nd prt rmt cmptrs, sndng th thntctn tkns (.g. srnm nd psswrd) fr ths ccss t ths cmptrs crss pblc ntwrk n n nscrd wy, pss grt rsk f 3rd prts btnng th psswrd nd chvng th sm lvl f ccss t th rmt systm s th tlnt sr. Scr Shll mtgts ths rsk thrgh th s f ncryptn mchnsms tht r ntndd t hd th cntnts f th trnsmssn frm n bsrvr, vn f th bsrvr hs ccss t th ntr dt strm.
SSH ws frst dsgnd n 1995 by Fnnsh cmptr scntst Tt Ylönn (t rplc th Tlnt ntwrk prtcl). Sbsqnt dvlpmnt f th prtcl st prcdd n svrl dvlpr grps, prdcng svrl vrnts f mplmnttn. Th prtcl spcfctn dstngshs tw mjr vrsns, rfrrd t s SSH-1 nd SSH-2. Th mst cmmnly mplmntd sftwr stck s pnSSH, rlsd n 1999 s pn-src sftwr by th pnBSD dvlprs. mplmnttns r dstrbtd fr ll typs f prtng systms n cmmn s, ncldng mbddd systms.
SSH pplctns r bsd n clnt–srvr rchtctr, cnnctng n SSH clnt nstnc wth n SSH srvr. SSH prts s lyrd prtcl st cmprsng thr prncpl hrrchcl cmpnnts: th trnsprt lyr prvds srvr thntctn, cnfdntlty, nd ntgrty; th sr thntctn prtcl vldts th sr t th srvr; nd th cnnctn prtcl mltplxs th ncryptd tnnl nt mltpl lgcl cmmnctn chnnls.