[51447] in cryptography@c2.net mail archive
deriving multiple keys from one passphrase
daemon@ATHENA.MIT.EDU (Travis H.)
Tue Oct 10 11:24:40 2006
X-Original-To: cryptography@metzdowd.com
X-Original-To: cryptography@metzdowd.com
Date: Mon, 9 Oct 2006 18:35:43 -0500
From: "Travis H." <solinym@gmail.com>
To: Cryptography <cryptography@metzdowd.com>
What is the accepted way to derive several keys from a user-supplied input?
Or, can you see anything wrong by prepending a counter to the passphrase
and hashing it to create derived keys?
k_n = hash(n || passphrase)
I suppose a faster system would involve using hash(passphrase) as the
key and encrypting a counter (assuming that hashes are slower than
block ciphers).
k_n = E(hash(passphrase), n)
Both seem vulnerable to dictionary attacks, and it's not immediately clear
to me how I could prevent them, or if that's even possible.
Terry Ritter suggested using CRCs over the passphrase, but I haven't really
analyzed that method at all.
Any opinions?
--
Enhance your calm, fellow citizen; it's just ones and zeroes.
Unix "guru" for rent or hire -><- http://www.lightconsulting.com/~travis/
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