4.4BSD/usr/src/Domestic/man/crypt.0.1

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
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7th Edition               April 22, 1991                        2