OSEC

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Crypto Archives: Re: Chalange to Tim May was: Re: Frequency Tab

Re: Chalange to Tim May was: Re: Frequency Tables

Brad Kemp (kempindusriver.com)
Wed, 20 Oct 1999 11:29:00 -0400

At 08:19 PM 10/19/99 EDT, ANTGamezaol.com wrote:
>Write your own code to encrypt a message, note: this code must be completely
>your own not something someone wrote or compiled a DLL for or any other such
>thing, I will do the same, then chose a publicly available book in English,
>type the first 3 pages in a plain windows text format, then encrypt it with
>your code and send the ciphertext to the list. then e-mail your code for
>your encryption to the list, I will do the same, the first one to gain the
>others plain text wins the challenge upon this happening the winner will
>supply to the list the passphrase for his message and the title of the book
>he chose it being confirmed that the supplied encryption code and passphrase
>produce a proper plaintext he will be declared the winner if said code and
>passphrase does not produce a proper copy of the plaintext, the winner will
>forfeit. You have been challenged, now it is a matter of honor.

#include <stdio.h>
main(argc, argv)
{
        char * key = argv[2];
        int len = atoi(argv[1]);
        while(len--)
                putchar(*key++ ^ getchar());
}

output:

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
It continues like this for some 3 pages.

You cannot break this code without the pass phrase, you cannot be sure of
anything you decipher is the correct plain text. In fact, I could, by changing
the key, make the plain text anything.

You need to do a bit of studying before you make such useless challenges.
I suggest Schneier's Applied Cryptography as a starting point.

Brad

--- -- --
Brad Kemp
Indus River Networks, Inc. BradKempindusriver.com
31 Nagog Park 978-266-8122
Acton, MA 01720 fax 978-266-8111

This archive was generated by hypermail 2.0b3 on Wed Oct 20 1999 - 13:18:41 CDT