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Annotation of cci/usr/src/man/man1/crypt.1, revision 1.1.1.1

1.1       root        1: .TH CRYPT 1 "18 January 1983"
                      2: .SH NAME
                      3: crypt \- encode/decode
                      4: .SH SYNOPSIS
                      5: .B crypt
                      6: [ password ]
                      7: .SH DESCRIPTION
                      8: .I Crypt
                      9: reads from the standard input and writes
                     10: on the standard output.
                     11: The
                     12: .I password
                     13: is a key that selects a particular transformation.
                     14: If no
                     15: .I password 
                     16: is given,
                     17: .I crypt
                     18: demands a key from the terminal and turns
                     19: off printing while the key is being typed in.
                     20: .I Crypt
                     21: encrypts and decrypts with the same key:
                     22: .PP
                     23:        crypt key <clear >cypher
                     24: .br
                     25:        crypt key <cypher | pr
                     26: .PP
                     27: prints the clear.
                     28: .PP
                     29: Files encrypted by
                     30: .I crypt
                     31: are compatible with those treated by the editor
                     32: .I ed
                     33: in encryption mode.
                     34: .PP
                     35: The security of encrypted files depends on three factors:
                     36: the fundamental method must be hard to solve;
                     37: direct search of the key space must be infeasible;
                     38: `sneak paths' by which keys or cleartext can become
                     39: visible must be minimized.
                     40: .PP
                     41: .I Crypt
                     42: implements a one-rotor machine designed along the lines
                     43: of the German Enigma, but with a 256-element rotor.
                     44: Methods of attack on such machines are known, but not widely;
                     45: moreover the amount of work required is likely to be large.
                     46: .PP
                     47: The transformation of a key into the internal
                     48: settings of the machine is deliberately designed to
                     49: be expensive, i.e. to take a substantial fraction of
                     50: a second to compute.
                     51: However,
                     52: if keys are restricted to, for example, 
                     53: three lower-case letters,
                     54: then encrypted files can be read by expending only
                     55: a substantial fraction of
                     56: five minutes of machine time.
                     57: .PP
                     58: Since the key is an argument to the
                     59: .I crypt
                     60: command,
                     61: it is potentially visible to users executing
                     62: .IR ps (1)
                     63: or a derivative.
                     64: To minimize this possibility,
                     65: .I crypt
                     66: takes care to destroy any record of the key
                     67: immediately upon entry.
                     68: No doubt the choice of keys and key security
                     69: are the most vulnerable aspect of
                     70: .I crypt.
                     71: .SH FILES
                     72: /dev/tty for typed key
                     73: .SH "SEE ALSO"
                     74: ed(1),
                     75: makekey(8)
                     76: .SH BUGS
                     77: There is no warranty of merchantability nor any warranty
                     78: of fitness for a particular purpose nor any other warranty,
                     79: either express or implied, as to the accuracy of the
                     80: enclosed materials or as to their suitability for any
                     81: particular purpose.  Accordingly, Bell Telephone
                     82: Laboratories assumes no responsibility for their use by the
                     83: recipient.   Further, Bell Laboratories assumes no obligation
                     84: to furnish any assistance of any kind whatsoever, or to
                     85: furnish any additional information or documentation.

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