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That's because AES is not a password-based encryption algorithm. It's a block cipher. It may seem like a detail, but such details matter. In cryptography, and in security in general, details often matter. AES is a pair of functions, each of which takes a key and a 128-bit message and produces a 128-bit message. The two functions are called encryption and ...


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In the event this is a homework question, I'll give an answer that would be improbably correct so you may not use it. ;) But maybe people won't accuse you of asking a homework question if you would source where you got the example? The password and the key are two different things. Early cryptographic implementations used the password directly. This is ...


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There are two things here: Encryption uses mode of operation, and not "AES alone". Some of them are randomized by an initialization vector - that means the encryption of the same text under the same algorithm is still randomized and not deterministic. The encryption methods take care of that. You only need the correct key to decrypt. Passwords are not ...


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In addition to Ilmari's excellent answer I would like to address your questions and clarify some points for you: I am trying to understand why is bcrypt called a Key Derivation Function? Because it derives a key from given input. This key is then used as unique value for a password in the case it is used for password hashing. bcrypt is a Password Based ...


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It's called a key derivation function because that's what you'd typically use its output for — as a key for some other cryptographic algorithm. (Of course, you can also use the output of Bcrypt for other purposes, e.g. storing it in a database as a password hash, but that's really a secondary use case.) In general, key derivation functions (KDFs) ...


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I don't think it is a good idea, for two main reasons. Firstly, you are basing your security on the obscurity of a parameter that was not designed initially for being secret, which is a risky practice. It is similar to hiding the salt. Secondly, following your example, you may in principle think that a random number of iterations between 10 and 100,000 is ...


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With a KDF meeting its objectives, the only way the leak of the persisted key compromises the confidentiality of the other is correctly identified in the question: a password guess can be checked at the cost of one evaluation of the KDF based on the leaked key and its corresponding salt (and assuming the password's entropy is significantly less than the ...



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