# Tag Info

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A nonce ensures that the same plaintext will always be mapped to different ciphertexts using the same key. Schemes requiring a nonce should always get a nonce, even for file-encryption you can't guarantee that your users won't encrypt the very same file twice, for reasons only known to them. Now to answer your questions: Authenticated encryption (AE) is ...

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The key exchange should also be authenticated. $\:$ GCM mode would mostly do that; however, you should authenticate an indication of which message is for Diffie-Hellman. (For example, you could use associated_data = 1 for the Diffie-Hellman messages and associated_data = 0 || application's_associated_data for application-level messages.)

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I finally found out what you're asking for: A specific (working?) related-key attack on AES! For this answer I changed the notation a bit: AES-DEC(K,P) got converted to $D_K(P)$ derived_key_X got converted to $DK_X$ seed (which is known) got converted to $S_K$ chosen_seed got converted to $S_C$ temp_key got converted to $K_T$ Now the answer: AES by ...

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The below is assuming a natural language is the one that has sentences from a well defined dictionary for that language (ex: oxford dictionary for english ). We can do this with the standard approach for FPE i.e $rank-encrypt-derank$. Build a $key-value$ pair map of all the words in the language of preference Where $key$ is the number and $value$ is the ...

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Yes; virtually all of them. Quantum computers give a quadratic speedup on a general search problems (so key lengths need to double), but I don't know of any symmetric schemes in actual use for which quantum computation gives a bigger speedup.

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