[Cryptography] Compression before encryption?

[Jonathan Katz]

On Fri, Jan 9, 2015 at 7:22 AM, Stephan Neuhaus <stephan.neuhaus at zhaw.ch> wrote:
> Dear list,
>
> I have come across the recommendation to "compress before you encrypt", on
> the grounds that this makes plaintext recognition through frequency analysis
> much harder.
>
> However, compression algorithms surely have easily recognisable headers,
> right?  Also, I seem to recall a paper that did interesting things with
> encrypted compressed plaintext, but I can't recall any details.
>
> So, does any one know what paper I might be referring to?  Or is there any
> other hard evidence (not personal opinion, however well-informed, please)
> that compression before encryption does or does not help?

See http://en.wikipedia.org/wiki/CRIME for some of the dangers of
doing compression before encryption.

> Thanks in advance,
>
> Stephan
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