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Imagine that you are responsible for implementation of a new security system in a company which boss insists on having new encryption algorithm.

Here are couple of solutions which has been presented to you by other companies offering such services:

  1. No opponent having a cryptogram will ever know the key used to make it.
  2. No opponent having a cryptogram will ever know matching open text.
  3. No opponent having a cryptogram will be able to say anything about any of the symbol of open text
  4. No opponent having a cryptogram will be able to obtain any useful information.

Each of the companies offers the same price, which offer would you choose? Justify your answer. If you do not like any of the offers above, write a suitable phrase guaranteeing safety of the encryption algorithm.

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From the FAQ "You should only ask practical, answerable questions based on actual problems that you face. Chatty, open-ended questions diminish the usefulness of our site and push other questions off the front page." So, I am going to say this questionis off-topic. Perhaps edit so it is not so chatty, open-ended, etc. – mikeazo♦ Feb 21 at 15:10

closed as not constructive by CodesInChaos, Maeher, mikeazo♦ Feb 21 at 15:11

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1 Answer

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I guess 4 - I mean, wouldn't knowing either the key, the plaintext or any symbol be considered useful? As I see it, 4 encompasses all of the previous options.

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However depending on the circumstances it might not be instantiable. An upper bound on the plaintext size could be considered useful. – Maeher Feb 21 at 18:04

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