| One-time-pads are - simplified - randomly generated strings. If they are implemented on a computer, they will be random sequences of 0's and 1's, for example: |
0 1 0 0 0 1
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ONE-TIME-PAD |
| A message is encrypted by adding the one-time-pad to the message, in the case of zeros and ones, using the logical XOR. |
1 0 0 1 1 1
1 1 0 1 1 0
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KLARTEXT > xor with the OTP turns out:
CIPHERTEXT |
The good thing about one-time-pads is: This algorithm is unbreakable, given any cipher text, it can be decrypted to any message and nobody can decide what the original message was.
The bad thing however: Never use a ONE-TIME-pad twice!
This algorithm can be used in a high security environment for a two-party communication if the expenses of the secure transmission of the OTP's can be justified with the increase in security. Additionally, a nonpredictable source of random strings is required. Otherwise new attack possibilities can be exploited.
There is no sense to publish an unbreakable challenge at this place. But since the OTP has the weakness, that the OTP may never be reused, we'll use this weakness as others have before. |
How-To
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The CC can be started here. Its aim is, to decipher given messages using some hints.
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Non-registered users get a new challenge each time they start the challenge, while registered
get the same challenge until it is solved or deleted (see the menu on top of the game).
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Registered users can use the save- button in the challenge to save the current state and
continue playing later.
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The programmers interface returns on http://www.mystery-twister.com/cc1-4/interface.php the game data in a parser friendly format. Using the call http://www.mystery-twister.com/cc1-4/interface.php?check=ABC... one can check his results. (The zeros have to be replaced by the result.) The values (knapsack and PIN) are a little bit bigger than those used for the Flash game. Else, Brute Force attacks would be too easy.
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