Cipher Suite Practices and Pitfalls

Cipher Suite Practices and Pitfalls It seems like every time you turn around there is a new vulnerability to deal with, and some of them, such as Sweet32, have required altering cipher configurati...
Updated Jun 06, 2023
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DM706_346160
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May 01, 2019

Hi MegaZone,

 

This is a great article, I really appreciate you taking the time to explain the individual components of a cipher suite.

 

I've been working on tightening of some of my SSL profiles and have come to the conclusion that if I want Qualys to give me no "weak" ciphers that I have to drop CBC support. However, doing so, with the other requirement that I need 2048bit DHE or ECDHE as well, that I drop support for Windows 7 and IE11. In a year or two that will obviously be less of a problem, however, today I think it is. With these cipher requirements, I get literally 2 ciphers.... "ECDHE+AES-GCM:@STRENGTH"

 

In your last comment you stated "CBC ciphers aren't inherently vulnerable (unlike RC4), the vulnerabilities are implementation specific. You can have CBC ciphers without being vulnerable"

 

Can you expand on that statement a little more? I'd like to know if, in my scenario, that CBC is actually weak or if its just ssllabs.com doing a blanket "if cipher.instr('CBC') then 'WEAK'"...