CRYPT(1) BSD Reference Manual CRYPT(1) NNAAMMEE crypt - encode/decode SSYYNNOOPPSSIISS ccrryypptt [ password ] DDEESSCCRRIIPPTTIIOONN TThhiiss iinntteerrffaaccee iiss oobbssoolleetteedd bbyy bbddeess((11)).. _C_r_y_p_t reads from the standard input and writes on the standard output. The _p_a_s_s_w_o_r_d is a key that selects a particular transformation. If no _p_a_s_s_w_o_r_d is given, _c_r_y_p_t demands a key from the terminal and turns off printing while the key is being typed in. _C_r_y_p_t encrypts and decrypts with the same key: crypt key <clear >cypher crypt key <cypher | pr will print the clear. Files encrypted by _c_r_y_p_t are compatible with those treated by the editor _e_d in encryption mode. The security of encrypted files depends on three factors: the fundamental method must be hard to solve; direct search of the key space must be infeasible; `sneak paths' by which keys or cleartext can become visible must be min- imized. _C_r_y_p_t implements a one-rotor machine designed along the lines of the German Enigma, but with a 256-element rotor. Methods of attack on such machines are known, but not widely; moreover the amount of work required is likely to be large. The transformation of a key into the internal settings of the machine is deliberately designed to be expensive, i.e. to take a substantial fraction of a second to compute. However, if keys are restricted to (say) three lower-case letters, then encrypted files can be read by expending only a substantial fraction of five minutes of machine time. Since the key is an argument to the _c_r_y_p_t command, it is potentially visible to users executing _p_s(1) or a deriva- tive. To minimize this possibility, _c_r_y_p_t takes care to destroy any record of the key immediately upon entry. No doubt the choice of keys and key security are the most vulnerable aspect of _c_r_y_p_t_. 7th Edition April 22, 1991 1 CRYPT(1) BSD Reference Manual CRYPT(1) FFIILLEESS /dev/tty for typed key SSEEEE AALLSSOO ed(1), crypt(3), makekey(8) BBUUGGSS There is no warranty of merchantability nor any warranty of fitness for a particular purpose nor any other war- ranty, either express or implied, as to the accuracy of the enclosed materials or as to their suitability for any particular purpose. Accordingly, Bell Telephone Laborato- ries assumes no responsibility for their use by the recip- ient. Further, Bell Laboratories assumes no obligation to furnish any assistance of any kind whatsoever, or to furnish any additional information or documentation. 7th Edition April 22, 1991 2