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80 lines
2.9 KiB
Groff
80 lines
2.9 KiB
Groff
.\" Copyright (c) 1989, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)caesar.6 8.2 (Berkeley) 11/16/93
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.\" $FreeBSD$
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.\"
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.Dd November 16, 1993
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.Dt CAESAR 6
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.Os
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.Sh NAME
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.Nm caesar , rot13
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.Nd decrypt caesar ciphers
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.Sh SYNOPSIS
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.Nm
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.Op Ar rotation
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.Nm rot13
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.Sh DESCRIPTION
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The
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.Nm
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utility attempts to decrypt caesar ciphers using English letter frequency
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statistics.
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.Nm Caesar
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reads from the standard input and writes to the standard output.
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.Pp
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The optional numerical argument
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.Ar rotation
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may be used to specify a specific rotation value.
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If invoked as
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.Nm rot13 ,
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a rotation value of 13 will be used.
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.Pp
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The frequency (from most common to least) of English letters is as follows:
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.Pp
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.Bd -ragged -offset indent
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ETAONRISHDLFCMUGPYWBVKXJQZ
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.Ed
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.Pp
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Their frequencies as a percentage are as follows:
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.Pp
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.Bd -ragged -offset indent
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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),
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D(3.8), L(3.4), F(2.9), C(2.7), M(2.5), U(2.4), G(2),
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P(1.9), Y(1.9),
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W(1.5), B(1.4), V(.9), K(.4), X(.15), J(.13), Q(.11), Z(.07).
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.Ed
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.Pp
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Rotated postings to
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.Tn USENET
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and some of the databases used by the
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.Xr fortune 6
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program are rotated by 13 characters.
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