Re: Questions about misuse vulnerabilities

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Phil Grundig wrote:
> 1. I've read that you are not supposed to use the same gpg key on
> different loop-aes volumes. Why? Even if the volumes contains some (but
> not all) data in common, how does that help an attacker?

Identical encryption keys + identical plaintext data + same offset from
beginning of a disk partition leads to identical ciphertexts. Identical
ciphertexts leak information about plaintext.

> 2. How long in bytes does a known plaintext string encrypted at a known
> position on a v3.x loop-aes encrypted device have to be to allow an
> attacker to reverse engineer what the v3.x plaintext multiline key must
> be?

16 bytes of known plaintext starting at any (except first) 16 byte boundary
on a disk sector allows adversary to try brute force attack for one AES key.
But 128/192/256 bits of key space is too much to brute force.

-- 
Jari Ruusu  1024R/3A220F51 5B 4B F9 BB D3 3F 52 E9  DB 1D EB E3 24 0E A9 DD

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Linux-crypto:  cryptography in and on the Linux system
Archive:       http://mail.nl.linux.org/linux-crypto/


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