Vigenere Encryption

This is a discussion on Vigenere Encryption within the C++ Programming forums, part of the General Programming Boards category; I am working with the above mentioned encryption algorith... DO you think that encrypting an encrypted message several times will ...

  1. #1
    Its not rocket science vasanth's Avatar
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    Vigenere Encryption

    I am working with the above mentioned encryption algorith...



    DO you think that encrypting an encrypted message several times will increase the security...

  2. #2
    and the hat of wrongness Salem's Avatar
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    Shouldn't you be reading the various cryptography FAQs?

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    Its not rocket science vasanth's Avatar
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    I am.. Even purchased many books.. But none speaks about this.. Only triple DES has slightly the same topic.. But it instead of encrypting again.. it decrypts it with a wrong key(second key) to make it more secure... but i want to know wheather encrypting it twice or many other times makes it more secure...

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    Well I think that depends on the encryption.

    If is something that is done to each letter, like a ceasarian shift, then doing it again won't help. It could still be decrypted by one key, the product of the two used.

    If, on the other hand, a character's position in a string is applicable, and is done in a manner that is related to that position, then another layer of encryption would increase the encryptedness, although you get diminishing returns.

    For example, a single Q shift on:

    Cprog boards are fun

    would produce:

    V[tph npstfd str gin

    Another q shift gives you:

    B]yj m[dygf dyt ho,

    But if you Q shift this back using -2, in one pass you get:

    Cprog boards are fun

    So a Q shift is not improved by multiple passes. But, if a letter's position mattered, like for example, a simple incremented shift:

    234567890

    325648907

    And again:

    236459078

    It now has to be unshifted in two passes, and can be considered safer.

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