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| Title: | Mathematics at DEC |
|
| Moderator: | RUSURE::EDP |
|
| Created: | Mon Feb 03 1986 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 2083 |
| Total number of notes: | 14613 |
332.0. "Anyone for Cryptanalysis?" by SPEEDY::BRETT () Mon Sep 16 1985 14:54
The following piece of text is from the journal "Cryptologia" (to reduce
the temptation to look it up, I won't give the issue...)
It is the enciphering, via a vigenere cipher, of a normal english message.
I include it here in case there are any readers of this notes file who care
to try their hand at it.
ATFCX DAAIT OLPYD NPDSG
DYIRW TNIXE IQGPQ SXCEB
DQAKP YTFPE HCHSO SAOSF
PCERW PAAIT OLPYD NPDSG
DYODW TSRXX EYIAE PXWOD
QPILV UUBVP DLDET MWLVC
ATVCS ZLGKP RUTYD CAWHM
AXEQ
/Bevin
APPENDIX: VIGENERE ENCIPHERING
A caesar substitution is one where a simple shift of the standard alphabet
is used to encipher the message. The alphabet is not scrambled.
For example...
plain text letter ABCDEFGHIJKL...
cipher equivalent DEFGHIJKLMNO...
which would map jail --> MDLO
A vigenere encipherment uses a series of caesar substitutions, the first
of which is applied to the first letter of the text, the second to the second
etc. restarting after some number of them. For example, a period 2 vigenere
might be...
plain text letter ABCDEFGHIJKL...
cipher equivalent_1 DEFGHIJKLMNO...
cipher equivalent_2 BCDEFGHIJKLM...
which would map jail --> MBLM
The problem therefore is to find the period and the amount of slide
each caesar substitution has
| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 332.1 | | --UnknownUser-- | | Tue Sep 17 1985 16:39 | 0 |
| 332.2 | | BEING::POSTPISCHIL | | Tue Sep 17 1985 16:39 | 6 |
| Re .1:
I don't think you read all of .0!
-- edp
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| 332.3 | | TURTLE::GILBERT | | Tue Sep 17 1985 23:14 | 6 |
| re: .-1
Oops, I'd mistaken the "more..." as the "End of note".
re: .0
I have a solution! To prove this, without giving too much away:
the string "ea" appears in the plaintext exactly twice.
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