Entropy output from 256-bit Argon2 input

Asked Nov 15 '23 at 22:38

Active Nov 16 '23 at 16:12

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I would like to deterministically derive two different 256-bit keys from a single passphrase -- one used as an ECDSA private key, the other as a symmetric key for AES-GCM.

Would a KDF output sufficient bits of entropy, given a 256-bit input? I'm planning to use Argon2, but I'd be happy to use another KDF if necessary.

The passphrase will be generated using a Diceware wordlist (.txt) (7776 possible words), so if I understand it correctly, a 256-bit passphrase will be $ \log _{7776}{(2^{256})} \approx 20$ words long.

asked Nov 15 '23 at 22:38

Astrochamp

2

KDFs don't increase the entropy, even may decrease it. Argon2 is fine with different salts or use HKDF-Expand only since you have a strong password. Multiple AES Key Derivation from a master key – kelalaka Nov 15 '23 at 22:53
1

@kelalaka thank you, HKDF-Expand looks perfect for my application! – Astrochamp Nov 16 '23 at 00:10

Entropy output from 256-bit Argon2 input

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