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4

The definitions are not all universal and there is quite some overlap. The clearest definition is for PRG, which is the (synchronous) stream cipher model. A PRG maps a secret value to a long, random-looking keystream, so that an attacker cannot predict any part of the keystream from knowing other parts of it. For a precise definition, you can see the ...


4

I will assume you mean the nonce that bitcoin miners iterate. Depending on e.g. wallet software other salts or nonces may be involved. That nonce is only used once, because every miner1 will be hashing a different transaction block (hash) – one which sends the reward for solving the proof of work to their address. A miner could reuse a nonce but they would ...


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 ...


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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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