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Skytale cipher

by chargrill (Parson)
on Apr 04, 2006 at 04:28 UTC ( [id://541075]=obfuscated: print w/replies, xml ) Need Help??

A slightly less simple obfuscation for a slightly less simple substitution cipher. The next stop in my tour of old forgotten encryption ciphers is this skytale implementation. This either takes a file as a parameter to encrypt in skytale, or provided no input encrypt's it's __DATA__.

#!/usr/bin/perl open DATA,$ARGV[0]if$ARGV[0];$;=$0=~y~a-z~~;map{m'(\d+)(?{$*=chr$,+65; +push@{$*}, $^N;$.{$*}++;$,=$,<$;?++$,:0})'}grep!/^10$/,map ord,split//,join'',<DA +TA>; print join '' , map chr , @ $_ for 'A' .. ( sort keys ( % . ) ) [ -1 ] ; pr +int "\n" ; __DATA__ In cryptography, a scytale (also known as skytale) is a tool used to p +erform a transposition cipher, consisting of a cylinder w/ a strip of paper wou +nd around it on which is written a message across the windings, with the ciphert +ext consisting of the unwound paper. This is one way to implement such a +cipher.

$,=42;for(34,0,-3,9,-11,11,-17,7,-5){$*.=pack'c'=>$,+=$_}for(reverse s +plit//=>$* ){$%++?$ %%2?push@C,$_,$":push@c,$_,$":(push@C,$_,$")&&push@c,$"}$C[$# +C]=$/;($#C >$#c)?($ c=\@C)&&($ C=\@c):($ c=\@c)&&($C=\@C);$%=$|;for(@$c){print$_^ +$$C[$%++]}

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Re: Skytale cipher
by turo (Friar) on May 04, 2006 at 04:02 UTC

    Good Implementation :-) ...

    Your scitale has a width (W) denoted by the number of lower cups characters the filename has, plus one.

    Then, you use W arrays for storing each character from the plaintext; first character on the plaintext to the array[0], the second to the array1, and so on up to reach the arrayW-1, the next char to the first array[0], etc.

    Cool!, i've made an implementation of this cipher (i like too much these topic) a long time ago (i do not remember where did i put it), but for sure my impl. was unobfuscated an i think i made W reads of the plaintext for encoding and decoding. Not too optimal, but easy to understand :-) (ummm... i don't rememeber if i've made it in perl ... or it was in awk? ... anyway)

    perl -Te 'print map { chr((ord)-((10,20,2,7)[$i++])) } split //,"turo"'

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