[cryptography] One Time Pad Cryptanalysis

Ben Laurie ben at links.org
Thu Oct 3 16:46:24 EDT 2013


On 3 October 2013 14:13, Florian Weimer <fw at deneb.enyo.de> wrote:

> > On 02/10/13 at 08:51am, Florian Weimer wrote:
> >> There is widespread belief that compressing before encrypting makes
> >> cryptanalysis harder, so compression is assumed to be beneficial.
>
> > Any academic references?
>
> Applied Cryptography (2nd edition) contains this:


Oh boy.


>


> | 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.


> |
> |   Encryption is time-consuming; compressing a file before encryption
> |   speeds up the process.
>

I haven't benchmarked it, but I find it unlikely that compression is faster
than encryption.


> | The important thing to remember is to compress before encryption. […]
>

Obvious.


>
> Schneier doesn't cite any references for these claims, unfortunately.
>
> Bergen and Hogan, "A Chosen Plaintext Attack on an Adapative
> Arithmetic Coding Compression Algorithm" (2002) cite Witten and
> Cleary, "On the privacy afforded by Adaptive Text Compression" (1988)
> and Jones, "An efficient coding system for long source sequences"
> (1981).  Neither paper appears to be available on the public Internet.
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