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Annotation of 43BSDTahoe/man/man1/crypt.1, revision 1.1.1.1

1.1       root        1: .\"    @(#)crypt.1     6.2 (Berkeley) 7/14/87
                      2: .\"
                      3: .TH CRYPT 1 "July 14, 1987"
                      4: .AT 3
                      5: .SH NAME
                      6: crypt \- encode/decode
                      7: .SH SYNOPSIS
                      8: .B crypt
                      9: [ password ]
                     10: .SH DESCRIPTION
                     11: .I Crypt
                     12: reads from the standard input and writes
                     13: on the standard output.
                     14: The
                     15: .I password
                     16: is a key that selects a particular transformation.
                     17: If no
                     18: .I password 
                     19: is given,
                     20: .I crypt
                     21: demands a key from the terminal and turns
                     22: off printing while the key is being typed in.
                     23: .I Crypt
                     24: encrypts and decrypts with the same key:
                     25: .PP
                     26:        crypt key <clear >cypher
                     27: .br
                     28:        crypt key <cypher | pr
                     29: .PP
                     30: will print the clear.
                     31: .PP
                     32: Files encrypted by
                     33: .I crypt
                     34: are compatible with those treated by the editor
                     35: .I ed
                     36: in encryption mode.
                     37: .PP
                     38: The security of encrypted files depends on three factors:
                     39: the fundamental method must be hard to solve;
                     40: direct search of the key space must be infeasible;
                     41: `sneak paths' by which keys or cleartext can become
                     42: visible must be minimized.
                     43: .PP
                     44: .I Crypt
                     45: implements a one-rotor machine designed along the lines
                     46: of the German Enigma, but with a 256-element rotor.
                     47: Methods of attack on such machines are known, but not widely;
                     48: moreover the amount of work required is likely to be large.
                     49: .PP
                     50: The transformation of a key into the internal
                     51: settings of the machine is deliberately designed to
                     52: be expensive, i.e. to take a substantial fraction of
                     53: a second to compute.
                     54: However,
                     55: if keys are restricted to (say)
                     56: three lower-case letters,
                     57: then encrypted files can be read by expending only
                     58: a substantial fraction of
                     59: five minutes of machine time.
                     60: .PP
                     61: Since the key is an argument to the
                     62: .I crypt
                     63: command,
                     64: it is potentially visible to users executing
                     65: .IR ps (1)
                     66: or a derivative.
                     67: To minimize this possibility,
                     68: .I crypt
                     69: takes care to destroy any record of the key
                     70: immediately upon entry.
                     71: No doubt the choice of keys and key security
                     72: are the most vulnerable aspect of
                     73: .I crypt.
                     74: .SH FILES
                     75: /dev/tty for typed key
                     76: .SH "SEE ALSO"
                     77: ed(1),
                     78: crypt(3),
                     79: makekey(8)
                     80: .SH BUGS
                     81: There is no warranty of merchantability nor any warranty
                     82: of fitness for a particular purpose nor any other warranty,
                     83: either express or implied, as to the accuracy of the
                     84: enclosed materials or as to their suitability for any
                     85: particular purpose.  Accordingly, Bell Telephone
                     86: Laboratories assumes no responsibility for their use by the
                     87: recipient.   Further, Bell Laboratories assumes no obligation
                     88: to furnish any assistance of any kind whatsoever, or to
                     89: furnish any additional information or documentation.

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