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A comment on Man Who Refused to Decrypt Hard Drives Still in Prison After Two Years. Parent comment

Re:Man Who Refused to Decrypt Hard Drives Still in Prison Af... by weinzierl on Saturday September 02, 2017 @09:29AM (#15155868)
> If the disk is encrypted how can they match file hashes?

This is an attack, which contemporary block based FDE doesn't really protect you well from. Bitlocker, FileFault, TrueCrypt, VeraCrypt basically operate on one disk block at at time and this means they cannot hide data patterns well. Or as Thomas Ptacek put it in his article "You Don't Want XTS" [1]

>It’s ECB-like. It can’t do a perfect job of providing privacy.

This is also why Thomas Ptacek and others are advocating that FDE is not a complete replacement for file based encryption.

> But that’s the big problem: sector-level encryption sucks. It’s messy, provides fewer security guarantees than conventional message encryption, and makes tradeoffs tailored to the challenges of encrypting disk sectors.

> Sector-level crypto is last-resort crypto.[1]

The Wikipedia article about ECB[2] (which is not used in current FDE) has a dramatic example where the image of the Linux penguin is clearly recognizable in the ciphertext.

[1] https://sockpuppet.org/blog/2014/04/30/you-dont-want-xts/

[2] https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation

[ Parent | on HN ]
Re:Man Who Refused to Decrypt Hard Drives Still in Prison Af... by wyager on Saturday September 02, 2017 @10:58AM (#15156272)
This is 100% wrong. XTS-mode AES absolutely protects you from known-plaintext attacks like the investigators apparently claim to have pulled off. I suspect we don't have the full description.
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Re:Man Who Refused to Decrypt Hard Drives Still in Prison Af... by weinzierl on Saturday September 02, 2017 @12:12PM (#15156712)
> XTS-mode AES absolutely protects you from known-plaintext attacks like the investigators apparently claim to have pulled off.

1. I didn't claim XTS-mode AES is vulnerable to known-plaintext attacks.

2. I don't believe the investigators claim to have pulled off a known-plaintext attack. What is your source for this?

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Re:Man Who Refused to Decrypt Hard Drives Still in Prison Af... by wyager on Saturday September 02, 2017 @12:21PM (#15156774)
You said:

> Bitlocker, FileFault, TrueCrypt, VeraCrypt basically operate on one disk block at at time and this means they cannot hide data patterns well.

This is wrong, but you claimed it. In the context of this thread (matching files on an encrypted disk with known unencrypted files), that's a known-plaintext attack.

Maybe you weren't aware you were making this claim, but you did.

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