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The best way to encrypt a seed in a db would be to use multiparty computation and heterogeneous computing (multiple core systems). The only other way would be to store them in plaintext, e.g. in a shadow password (non-public file).


I'll take this in parts: But this is clearly not the case when you're doing Encrypt Then Mac. When you do that you provide authentication to something that already has authentication (to decrypt we need to know the key). Encryption, by itself, does not provide authentication. why use a MAC when we can use a hash instead: E(m|h(m))? Here is a ...


Practically, because there some attacks possible on the cipher scheme (not possible against E anymore) that make it a bad idea in some cases to decrypt messages from arbitrary sources.


Yes, if your encryption algorithm is reasonable secure. Given fixed length messages (in your case the ciphertext), CBC-MAC is a secure MAC scheme, meaning that an attacker, without knowing the key, cannot produce a valid message-tag pair with non-negligible probability. Furthermore, according to this paper, Encrypt-then-MAC is the best procedure, while ...


In short: the question does not explain well the notion of asymmetry in ECC; and the exposition is not how Elliptic Curve Cryptography works. A reasoning sidestepping the notion of Discrete Logarithm Problem over a finite group can not really explain asymmetry as meant in ECC. Asymmetry is in the knowledge Alice and Bob have about the key, not asymmetry of ...


In cases where Alice and Bob are guaranteed to arrive at the same key, this is impossible: the function that takes Alice and Bob's private info as input, and produces the public transcript as output, must be a one-way function if the scheme is to be secure and if it always negotiates a shared key. If it sometimes fails, then you don't necessarily get a OWF; ...

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