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2

Yes, you can do that. Start by generating a random key and encrypting the data under that key. Now, you in turn encrypt that key with your password-derived key. The twist is that you include the already encrypted file in your PBKDF. So you generate a random key $k$ and then encapsulate it as $\mathcal{E}_{k'}(k)$, where \$k' = H(PBKDF(\text{password}) \| ...

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I have looked at some attacks on RC4 and be curious if some of them can be applied to Spritz as well. Does anybody else has analysed Spritz so far? Or is it far too early for results against Spritz? No third party analysis. Probably way too early. (Even the paper you linked is unpublished.) The answer may of course change any time. From the ...

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To answer the question "why does a block cipher use a Mode of Operation", we need to first examine the question "what is a block cipher?" A block cipher is a keyed operation that converts a string of N bits to a string of N bits (where N is usually fixed by the block cipher; for AES, N=128), in a way that, without the key, looks like a random permutation, ...

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I will try to not directly answer your question, but this exercise is so simple that it gets hard to help you without doing that. You are going to use a symmetric cipher (One-Time Pad - OTP), thus your initial step is to compute your key. This is given by the execution of the LFSR as you described, until a key-stream of the length of the message is ...

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For any typical stream cipher (including block ciphers in streaming modes like CBC / CFB / OFB / CTR), the time needed to encrypt a message consists of two parts: the time needed to set up the cipher, which is approximately constant, and the time needed to encrypt a chunk of the message (also approximately constant), multiplied by the number of chunks in ...

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