Article View: sci.crypt
Article #1333Re: DES Encryption/ Encrypting more than once.
From: Joseph Reuter
Date: Thu, 15 Oct 1992 19:47
Date: Thu, 15 Oct 1992 19:47
26 lines
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1666 bytes
In article <1992Oct15.144341.15104@rchland.ibm.com> lwloen@vnet.ibm.com writes: >[stuff deleted] >The simplest way to show this is to do Simple Substitution >ciphers. One can re-arrange the standard two alphabet key as >chains of substitutions. For instance, consider (for brevity) the following >simple substitution key > >ABCDEFGHIJK... for plaintext and >REPUBLICAND... for ciphertext. > >This has B->E->B (and hence, is B<->E), but G->I->A->R->morestuff->G. This >sort of irregular value for n is commonplace in ciphers. > This argument shows that the MINIMUM value of n is different for each plaintext character. However, the number of plaintext characters is finite (even in DEX it is 2^64, which is finite) and the least common multiple of the various n's has the property that repeating the substitution that many times will transform each plaintext character into itself. Far from disproving the original assertion, you have proved it! -- Joseph A. Reuter, Wizard-in-Training Speaking for myself from reuter@venice.sedd.trw.com "Olorin I was in my youth in the West that is forgotten." -- J.R.R. Tolkien "You can't win, you can't break even, and it's the only game in town."
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Newsgroups: sci.crypt Path: arc1-ca.pugleaf.net!sparky!uunet!hela.iti.org!usc!venice!reuter From: reuter@venice.sedd.trw.com (Joseph Reuter) Subject: Re: DES Encryption/ Encrypting more than once. Message-ID: <1992Oct15.194709.13679@venice.sedd.trw.com> Sender: Joseph A. Reuter Organization: TRW Systems Engineering & Development Division, Carson, CA References: <1992Oct15.144341.15104@rchland.ibm.com> Date: Thu, 15 Oct 1992 19:47:09 GMT Lines: 26