term% ls -F
term% cat index.txt
CRYPT(1)                    General Commands Manual                   CRYPT(1)

       crypt - encode/decode

       crypt [ password ]

       Crypt  reads from the standard input and writes on the standard output.
       The password is a key that selects a particular transformation.  If  no
       password  is given, crypt demands a key from the terminal and turns off
       printing while the key is being typed in.  Crypt encrypts and  decrypts
       with the same key:

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

       will print the clear.

       Files  encrypted by crypt are compatible with those treated by the edi‐
       tor ed in encryption mode.

       The security of encrypted files depends on three factors: the fundamen‐
       tal  method  must be hard to solve; direct search of the key space must
       be infeasible; `sneak paths' by which keys or cleartext can become vis‐
       ible must be minimized.

       Crypt  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 re‐
       quired 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 ex‐
       pending only a substantial fraction of five minutes of machine time.

       Since the key is an argument to the crypt command,  it  is  potentially
       visible  to  users  executing  ps(1) or a derivative.  To minimize this
       possibility, crypt takes care to destroy any record of the key  immedi‐
       ately upon entry.  No doubt the choice of keys and key security are the
       most vulnerable aspect of crypt.

       /dev/tty for typed key

       ed(1), makekey(8)

       There is no warranty of merchantability nor any warranty of fitness for
       a particular purpose nor any other warranty, either express or implied,
       as to the accuracy of the enclosed materials or as to their suitability
       for  any  particular purpose.  Accordingly, Bell Telephone Laboratories
       assumes no responsibility for their use by  the  recipient.    Further,
       Bell  Laboratories  assumes  no obligation to furnish any assistance of
       any kind whatsoever, or to furnish any additional information or  docu‐