[gentoo-server] easy explanation of the strength of 3DES (and perhaps also IDEA)?

[Zhang Weiwu]

Hello. I googled around with no luck. I wish there could be some very
easy explanation of cipher strengths so that I could answer questions
like 'how strong 3DES is' to novice users. Most results I could find are
too technical / mathematical. I want very simple explanation like this:

128 bit IDEA is very strong cipher. Normally, take a piece of encrypted
data, it would need one Pentium Xeon 2GHz personal computer xxxx years
to decrypt the data, this is as long as the age of the earth (or human,
or USA, whatever). Even if you could use the most powerful computer now
one the earth abcde (replace abcde with the computation power), you need
xxx (a number) of them to decrypt it in 5 years.

The above sort of explanation is not precise, and will not be accepted
by any engineer / software documentation, but it's enough to let the
users (who definitely not wishing to become expert or have a PhD on
math) get the feeling that the data is almost safe.

Another question: technically, how does IDEA compare to 3DES on cipher
strength and CPU usage? Is 3DES more safer than IDEA and cost more CPU time?