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Math Help - Question about encrypting text.

  1. #1
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    Question about encrypting text.

    I need to encrypt some text, the way in which i intend to do this is by applying a vigenere cipher and then an affine substituition. I was wondering if this would be strong enough. Is it better to use a larger or smaller size of plain text? i cant use OTP (DOHH!!)
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  2. #2
    Super Member Bacterius's Avatar
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    This is clearly not enough if you need decent security. Today's standards, in symmetric encryption, are the AES and Blowfish algorithms, which you can lookup on google, and in the asymmetric encryption field, the standards are RSA and possibly ECC (Elliptic Curve Cryptography).

    Of course, what I said holds if you need maximum security for critical stuff ... if you just want to protect your information from the guy next door, just use your cipher, it should be enough.

    The less plaintext you encrypt, the less information the adversary has. However, if it is too small, it can also be predicted. You must choose the most appropriate block size for your uses.
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  3. #3
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    Quote Originally Posted by ravenboy View Post
    I need to encrypt some text, the way in which i intend to do this is by applying a vigenere cipher and then an affine substituition. I was wondering if this would be strong enough. Is it better to use a larger or smaller size of plain text? i cant use OTP (DOHH!!)
    Security also heavily depends on the size of the key (password) and the way it is managed. One reason why RSA is widely used lies in the fact that it handles this question pretty well with the distinction between public and private keys; this enables its use for crypted communication between computers. With Vigenère cypher, the same key is needed to encypher and decypher, so that one needs to give the key to whoever the message is sent to; but how? Encrypt the key? ...but how?

    If you dispose of a safe way to transmit the key, if your key is randomly generated and at least as long as the text you're encyphering, then the code is simply unbreakable. Any violation to the previous conditions weakens the quality of the cypher. As Bacterius says, this is to be put in balance with the importance of your text.
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