Ciphers suites to diable

[Roberto Volsa]

Hello all
which of the following cipher suites is the weakest?
I should disable the weakest in order to adding more security on the system.
Obviously i need to forecast impacts in disabling the cipher suite, man pages are not so helpfull.

> openssl ciphers -v
DHE-RSA-AES256-SHA
DHE-DSS-AES256-SHA
AES256-SHA
EDH-RSA-DES-CBC3-SHA
EDH-DSS-DES-CBC3-SHA
DES-CBC3-SHA
DES-CBC3-MD5
DHE-RSA-AES128-SHA
DHE-DSS-AES128-SHA
AES128-SHA
IDEA-CBC-SHA
IDEA-CBC-MD5
RC2-CBC-MD5
DHE-DSS-RC4-SHA
RC4-SHA
RC4-MD5
RC4-MD5
RC4-64-MD5
EXP1024-DHE-DSS-DES-CBC-SHA
EXP1024-DES-CBC-SHA
EXP1024-RC2-CBC-MD5
EDH-RSA-DES-CBC-SHA
EDH-DSS-DES-CBC-SHA
DES-CBC-SHA
DES-CBC-MD5
EXP1024-DHE-DSS-RC4-SHA
EXP1024-RC4-SHA
EXP1024-RC4-MD5
EXP-EDH-RSA-DES-CBC-SHA
EXP-EDH-DSS-DES-CBC-SHA
EXP-DES-CBC-SHA
EXP-RC2-CBC-MD5
EXP-RC2-CBC-MD5
EXP-RC4-MD5
EXP-RC4-MD5


Thanks in advance
RV

[Matti_Kurkela]

If you are setting up a public site, you'll need to know what algorithms are most likely to be supported by the various client applications. It's no good to have a secure site, if it is inaccessible by your potential users.

To get up-to-date information, you should Google for recent research on cryptography and SSL/TLS usage.

For example, a search with words "crypto algorithm strength compare" produced this hit that looks useable for you:
http://www.imconf.net/imc-2007/papers/imc130.pdf

A quick summary:

Single-DES is far too weak, so you should disallow DES-CBC-SHA and DES-CBC-MD5.

Triple-DES (DES-CBC3-*) is still adequate, but inefficient: it's slower than other algorithms of equivalent strength. You should prefer something else over triple-DES, but you can still allow triple-DES if necessary for compatibility.

You should prefer -SHA over -MD5, although both SHA and MD5 seem to be still OK (so far) when used in the specific way SSL 3.0 and TLS 1.0 use them.

Whatever you do, avoid SSL version 2.0 if possible: that protocol version has serious flaws that can undermine the strength of any cipher used with it.

MK