[cryptography] Repeated Encryptions Considered.... ?

Jack Lloyd lloyd at randombit.net
Sun Jun 19 17:10:29 EDT 2011


On Sun, Jun 19, 2011 at 11:21:59PM +0300, Sampo Syreeni wrote:

> But that is the least of our worries today. Symmetric block ciphers 
> especially are so strong now that the weak link in overall security is 
> pretty much *always* somewhere else. After that, multiple encryption 
> does multiply the possibilities for other kinds of security breaks, like 
> side channel attacks and what not.

There is one case I have seen where encryption with independent
ciphers does make sense - for certification reasons. Currently
Tahoe-LAFS uses AES to encrypt content, however there is a plan to
encrypt all messages first with XSalsa20, then AES, so that side
channel attacks on AES are no longer relevant but allowing it to
remain buzzword compliant, in that there is a subset of people
knowledgable enough to know what AES is but not knowledgable enough to
know that AES isn't always the best idea.

-Jack



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