caesar/caesar.6

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  34 .\"     @(#)caesar.6    8.2 (Berkeley) 11/16/93
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  36 .Dd November 16, 1993
  37 .Dt CAESAR 6
  38 .Os
  39 .Sh NAME
  40 .Nm caesar ,
  41 .Nm rot13
  42 .Nd decrypt caesar cyphers
  43 .Sh SYNOPSIS
  44 .Nm
  45 .Op Ar rotation
  46 .Sh DESCRIPTION
  47 The
  48 .Nm
  49 utility attempts to decrypt caesar cyphers using English letter frequency
  50 statistics.
  51 .Nm
  52 reads from the standard input and writes to the standard output.
  53 .Pp
  54 The optional numerical argument
  55 .Ar rotation
  56 may be used to specify a specific rotation value.
  57 .Pp
  58 The frequency (from most common to least) of English letters is as follows:
  59 .Pp
  60 .Bd -filled -offset indent
  61 ETAONRISHDLFCMUGPYWBVKXJQZ
  62 .Ed
  63 .Pp
  64 Their frequencies as a percentage are as follows:
  65 .Pp
  66 .Bd -filled -offset indent
  67 E(13), T(10.5), A(8.1), O(7.9), N(7.1), R(6.8), I(6.3), S(6.1), H(5.2),
  68 D(3.8), L(3.4), F(2.9), C(2.7), M(2.5), U(2.4), G(2),
  69 P(1.9), Y(1.9),
  70 W(1.5), B(1.4), V(.9), K(.4), X(.15), J(.13), Q(.11), Z(.07).
  71 .Ed
  72 .Pp
  73 Rotated postings to
  74 .Tn USENET
  75 and some of the databases used by the
  76 .Xr fortune 6
  77 program are rotated by 13 characters.