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Very simple, attacks on the block cipher mode of operation do not translate to attacks on the block cipher itself. The block cipher is simply a component within the mode of operation after all. The only time where the block cipher may come under attack is if the key is somehow changed to a related key in the scheme. This is somewhat of an issue for AES-256 ...


An easier way to say what Ilmari Karonen said is: Choose the plaintext to be the identity matrix. Thus, when it is multiplied by the key, the resultant ciphertext will be the key it self.


I'd like to add Shamir's secret scheme here too. Basically, you'd encode your message using this scheme. Then you can create as many different key as you want to decode it. This is usually used with two or more part for decoding, but nothing prevents you from using only one part here. Compared to Ángel solution, the message does not grow depending on the ...


We don't know. Although it seems unlikely to the extreme that there is some kind of mathematical equation that gets easier to solve when the second key relies on the first key, we probably cannot prove it. So that's it for the theoretical problems. One practical problem is that when the key for confidentiality is obtained by the adversary (e.g. through a ...


Yes, it would be possible to identify Serpent or Twofish keys from round keys in memory, which are likely to exist in a software-only implementation optimized for speed (but not in hypothetical hardware implementations, and not necessarily in implementations optimized for RAM or code size). The Serpent round keys are 132 words of 32 bits, output by a ...


Yes, Serpent also does a deterministic well-known key expansion. So it should be possible to identify the sub keys in memory. You will want to know what implementation you are looking for since there is more than one sensible order for the key material to be in.


Although people could email you their public key, most people & organizations distribute their Public Keys by uploading them to keyservers enabling them to be searched and downloaded. OpenPGP's keyserver is great because it provides a predictable HTTPS path to grab public keys via script. Here's a script I wrote to automate adding Public Keys to a GPG ...

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