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In literature there are 2 ways to show the affine transform for a given polynomial, and that depends on the location of the MSB in the input as a polynomial. The polynomial representation of the full transformation, in the format of the original Rijndael paper, is: $b(x) = a(x)(x^7 + x^6 + x^5 + x^4 + 1) + (x^7 + x^6 + x^2 + x) ~~mod~~ x^8 + 1$ Where ...


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If I'm understanding things right you want something that can encrypt data at abritrary size with high speed. You have several options here: CTR mode. This turns any block cipher into a stream cipher allowing you to encrypt arbitrary amounts of data at high speeds. (cipher would be AES-128) a dedicated streamcipher like Salsa20 or ChaCha. They are ...


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"Invertibility of the cryptographic primitive" is just a fancy way of saying "you can decrypt things encrypted with that key." All the first sentence means is "if you can recover the key, you can decrypt anything encrypted with that key." As the second sentence points out, there are conceivably attacks where you can decrypt things encrypted with a key but ...


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Issues: It is going to be extremely easy to find $y$ as the GCD of every number of the ciphertext. The only way to avoid this is to make all the letters' associated numbers have a common factor, but then you can just divide out by said common factor (it'll mess with the successive letters, but we'll get to that later). Once you have a candidate value for ...



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