Solved

Is 256bit SSL backwards compatiable with legacy 128bit?

Posted on 2014-02-25
3
367 Views
Last Modified: 2014-03-03
Hi,

I want to enable 256bit encryption which my SSL certificate is capable of for Windows 2008 R2 server. With IIS7 to do 256 bit encryption, we have to ensure the cipher suit that is listed first is the following: TLS_RSA_WITH_AES_256_CBC_SHA, if I do this will old browsers / systems still be able to connect with legacy 128bit?

I don't want to stop people who can only achieve 128bit from connecting and using the website. How can I ensure that the site is 256bit and 128bit compatible?
0
Comment
Question by:jwleys
  • 2
3 Comments
 
LVL 33

Accepted Solution

by:
Dave Howe earned 500 total points
ID: 39887815
I am not sure you can prefer 256 bit without disabling 128.

Out of the box, servers usually honour the order the client sends its SSL cypher suites in.

For apache, you can override that with the SSLHonorCipherOrder directive (which causes Apache to use its own list order to determine the "best" match) but I am not aware of any matching directive for IIS7 - so if you have TLS_RSA_WITH_AES_256_CBC_SHA listed first, it will be supported, but if a client sends a 128 bit cypher first in its SSL cyphersuites list, that will be selected (if supported) even if 256 bit AES is available further down the list.

The following may be useful for your testing:
https://www.nartac.com/Products/IISCrypto/Default.aspx

it is a gui tool to adjust the suite order in the registry :)
0
 

Author Closing Comment

by:jwleys
ID: 39901298
Thank you, the documentation you provided is excellent, yes you are right as far as I can see from my testing you can't prefer 256 bit without disabling 128. But thanks anyway I am going to stick to 128bit for the time being.
0
 
LVL 33

Expert Comment

by:Dave Howe
ID: 39901438
sorry I couldn't give you a better answer, but IIS is not particularly configurable in this matter :(
0

Featured Post

IT, Stop Being Called Into Every Meeting

Highfive is so simple that setting up every meeting room takes just minutes and every employee will be able to start or join a call from any room with ease. Never be called into a meeting just to get it started again. This is how video conferencing should work!

Join & Write a Comment

This story has been written with permission from the scammed victim, a valued client of mine – identity protected by request.
Know what services you can and cannot, should and should not combine on your server.
Sending a Secure fax is easy with eFax Corporate (http://www.enterprise.efax.com). First, Just open a new email message.  In the To field, type your recipient's fax number @efaxsend.com. You can even send a secure international fax — just include t…
This tutorial demonstrates a quick way of adding group price to multiple Magento products.

743 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

12 Experts available now in Live!

Get 1:1 Help Now