[cryptography] One Time Pad Cryptanalysis

Florian Weimer fw at deneb.enyo.de
Thu Oct 3 17:13:23 EDT 2013

* Ben Laurie:

>> | 10.6 Compression, Encoding, And Encryption
>> |
>> | Using a data compression algorithm together with an encryption
>> | algorithm makes sense for two reasons:
>> |
>> |   Cryptanalysis relies on exploiting redundancies in the plaintext;
>> |   compressing a file brfore encryption reduces these redundancies.

> Yeah. So CRIME shows us how accurate this wild claim is.

And it's not even the first attack of this type.  I find the
application voice codecs particularly cute.

The recommendation is really puzzling.  With a modern cipher,
compression (even if it hasn't fingerprints of its own) should never
make cryptanalysis harder.  With a very weak cipher, it could make a
difference, but even in the mid-90s, you hopefully wouldn't use one,
even after consulting Applied Cryptography (which describes quite a
few of them, admittedly).

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