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3

Just use AES. It's hardware-accelerated and implementations have had ages to have flaws discovered and patched. More strongly, just use GPG to encrypt data at rest and just use TLS (>= 1.2, with appropriate AEAD ciphers) for data in motion. "If you're typing the letters A-E-S into your code, you're doing it wrong." Anything you build yourself is infinitely ...

0

Note: I won't recommend a specific library for these, because this would be off-topic and the risk would be there that this gets outdated sooner than later (especially as soon as CAESAR finishes). This is a very standard solution to the authentication problem although usually one does do both (e.g. passphrase and keyfile). On the conceptual level any ...

2

Actually, the strength of the derived key is likely to be limited by the strength of the password; for example, if the user selects the password "password", well, that's likely be to within the first couple that an attacker checks. However, if we assume that the password is stronger than what most people select, then the next limiting factor is $n$. The ...

2

No, you're not weakening your data in that case. You could even use ECB in to encrypt random data. Symmetric key wrapping often just uses ECB. But beware that it depends on how many bytes you encrypt. You may want to make sure all bytes are random (if you know the plaintext size in advance). Think about encrypting a single random byte and filling the rest ...

4

Password Based Encryption (PBE) is specified in e.g. RFC 2898 which specifies the "PKCS #5: Password-Based Cryptography Specification Version 2.0". Keys used for symmetric ciphers such as AES and Twofish should be fully randomized. Passwords, even strong ones, do not consist of randomized bits. So they need to be converted to ...

8

As typically implemented, PBE takes a low-entropy, user-supplied password, adds some entropy to it, and thus strengthens it before turning it into a key. This key can then be used for symmetric encryption. The problem is that the user's password often has so little entropy to start with. If an attacker learns the salt, digest method and quantity of ...

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