usr/man/cat1/crypt.0



CRYPT(1)            UNIX Programmer's Manual             CRYPT(1)


N\bNA\bAM\bME\bE
     crypt - encode/decode

S\bSY\bYN\bNO\bOP\bPS\bSI\bIS\bS
     c\bcr\bry\byp\bpt\bt [ password ]

D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
     _\bC_\br_\by_\bp_\bt reads from the standard input and writes on the stan-
     dard output.  The _\bp_\ba_\bs_\bs_\bw_\bo_\br_\bd is a key that selects a particu-
     lar transformation.  If no _\bp_\ba_\bs_\bs_\bw_\bo_\br_\bd is given, _\bc_\br_\by_\bp_\bt demands
     a key from the terminal and turns off printing while the key
     is being typed in.  _\bC_\br_\by_\bp_\bt encrypts and decrypts with the
     same key:

          crypt key <clear >cypher
          crypt key <cypher | pr

     will print the clear.

     Files encrypted by _\bc_\br_\by_\bp_\bt are compatible with those treated
     by the editor _\be_\bd 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 minimized.

     _\bC_\br_\by_\bp_\bt 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.  How-
     ever, 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 _\bc_\br_\by_\bp_\bt command, it is
     potentially visible to users executing _\bp_\bs(1) or a deriva-
     tive.  To minimize this possibility, _\bc_\br_\by_\bp_\bt 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 _\bc_\br_\by_\bp_\bt.

F\bFI\bIL\bLE\bES\bS
     /dev/tty for typed key

S\bSE\bEE\bE A\bAL\bLS\bSO\bO
     ed(1), crypt(3), makekey(8)


Printed 7/9/88            July 14, 1987                         1


CRYPT(1)            UNIX Programmer's Manual             CRYPT(1)


B\bBU\bUG\bGS\bS
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Printed 7/9/88            July 14, 1987                         2