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Mar
25
comment What is the difference between known-plaintext attack and chosen-plaintext attack?
@Giles, on the contrary, the key point is that in the most basic RSA public key cryptography, signing a plaintext is exactly the same mathematical operation as decrypting a ciphertext. Look it up.
Mar
24
comment What is the difference between known-plaintext attack and chosen-plaintext attack?
@Gilles, RSA is very much a cryptographic algorithm. Because of its many drawbacks, it's used as a building block, but it's not necessary to use anything else. The OP asked about chosen vs known plaintext attacks and one of the reasons RSA is used the way it is is because of the chosen plaintext attack it is vulnerable to, and thus it is a good example of how a chosen plaintext can do what a known plaintext cannot.
Jun
22
comment Is this password migration strategy secure?
I submitted an edit to this answer but it was rejected. If you will make the changes I'll accept this answer. All I'm asking is that you re-order the statements so that they go from most practical to least. Start with that the proposal seems like in improvement, then recommend scrypt as a better solution, then discuss the theoretical attack. Please also note that using a random new_secure_salt that changes each time would protect against that attack, since that is the recommended usage of bcrypt.
Jun
18
comment Is this password migration strategy secure?
Thanks! I like scrypt, but it's too new for me to trust right now and with this scheme we can migrate to scrypt later. In all the systems I'm looking at, an adversary could at best predict, but not choose, the old salt and has no control over the new salt (securely random and unique per user), so the attack would not be practical.