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1

With the numbering in your comment: 1 yes, 2 no. If you just need to encrypt files, use age if you can. I'm going to answer the rest of this in the context of using libsodium as your cryptographic library. You might have a different choice, like NaCl or , but any choice should support a high-level API like I'll describe. If your library doesn't, it's not ...


0

The more frequently you update keys, the less data is processed with any given key, and therefore the less impact the leak will have. This goes regardless of the purpose of the key: confidentiality, authentication, or anything else. For data authentication, renewing the key limits the amount of tainted data, where it might be impossible to tell legitimate ...


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All block ciphers leak information. No matter the mode used there is a limit on the amount of data that should be encrypted with a single key, irrespective of the number of different IVs used, in order to not leak too much information that an attacker might be able to determine some of the encrypted data. For AES, it seems that the limit seems to be around ...


3

Since antiquity (and, for ceremonial purposes, up to the present day) physical document have had seals affixed to them. In principle, these seals allow anyone, if he knows what he's looking for, to judge the authenticity of a document without consulting the authority that issued it. (In practice, there are obviously ways of producing convincing forgeries, ...


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Is there a way, then, of doing something like the above, but without the need for a central authority? Why, yes, we do have a way to solve that problem - we refer to it as a 'digital signature' Here's how it works: Select a signature algorithm, and come up with a public/private key pair for a signature algorithm With the private key, generate a signature ...


1

I'm unaware of any proof of impossibility (although it wouldn't surprise me if one existed), but the fundamental issue here is there's no fundamental way that "physical identity" and "digital identity" are bound together. In short, given any algorithm $\mathcal{A}$ which generates some "seal" (or some private information used to generate seals in the future),...


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