[Cryptography] Is there a good algorithm providing both compression and encryption at the same time?

[Hanno Böck]

On Thu, 7 May 2015 23:48:51 +0200
Natanael <natanael.l at gmail.com> wrote:

> The easier method is to just pre-encrypt, as that requires no special
> treatment in the lower layers. Just feed in the data to send. Then you
> don't need to worry about overzealous compression or dumb
> optimization. No strange edge cases of accidental activation /
> deactivation of compression.

The output of an encryption is usually indistinguishable from random
garbage. Random garbage doesn't compress.

The whole point of compression is to exploit structure in the data. The
point of encryption is to hide structure in data. So that cannot work
by definition.

The problem of compression and encryption is a hard one and as far as
I'm aware nobody came up with a good answer to that (except "just don't
compress", but it's an answer we might not like in many situations).

-- 
Hanno Böck
http://hboeck.de/

mail/jabber: hanno at hboeck.de
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