# Tag Info

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When using a salted, key-stretching KDF, like PBKDF2 or scrypt, you are in effect stretching both the salt and the password. That is to say, what you're calculating is $$\rm key = KDF(password, salt)$$ where changing either of $\rm password$ or $\rm salt$ requires the slow $\rm KDF$ function to be entirely recomputed. In fact, if changing the salt did ...

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scrypt uses PBKDF2 internally, so it's absolutely crucial to prevent nasty interactions. My suggestion would be a simpler scheme (using simplified syntax): $k = \mathrm{scrypt}(key, salt || 0x0) \oplus \mathrm{PBKDF2}(key, salt || 0x1)$ This does exactly what you want - that is, the output key has exactly the strength of the stronger of the two, without ...

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CD CD is collectively referring to the C and D Registers. Their use and operation while simultaneous is independent. C and D are concatenated together to specify PC2. Permuted Choice 2 PC2 is a selection permutation. You might notice that the first 24 bits of the selected Key are from the C Register (CD(1 to 28)) and the second 24 bits are from the D ...

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