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Daniel Nashed


Apple App Transport Security

Daniel Nashed  22 July 2015 09:50:30
Apple is introducing a new standard for their next OS versions.
App Transport Security (ATS) is planned for iOS 9 and OS X 10.11.

The current plan is to only support
  • TLS 1.2
  • >= 2048 bit RSA
  • SHA-256 signed web server certificates
  • ECDHE!!

TLS 1.2 is a good idea, 2048 RSA keys are a good idea and SHA-256 is also a good idea because SHA-1 is rated as insecure.

The general requirement for PFS ciphers  
( is a good idea from security point of view.
But not everyone is supporting ECDHE (Elliptic curve Diffie–Hellman). The normal DHE Ciphers should be perfectly be OK from security point of view.

Maybe Apple is just allowing ECHDE because they have less overhead compared to the normal DHE Ciphers.

On the other side if ECDHE ciphers would be compromised in any way this would leave us with no supported cipher suite at all for communication.

Usually the server is responsible for the order in which ciphers are selected. There are server settings (like in current Domino 9.0.1 versions) to allow the client to select the cipher order.

So in general having a short cipher list with only secure ciphers is a good idea to really ensure that a strong cipher is selected!

But that will leave out many applications and will put a lot of pressure on many vendors and also on administrators implementing the latest software versions on server side.

As an app developer you can change you application to allow less secure TLS versions and ciphers.
But if you are running a server and the application is build against a newer API without those exceptions you will have to provide this strong security standard.

See this link for details -->

The Domino 8.5.x stack will not support TLS 1.2 and and SHA-256 because the code base does not include and SHA-256 support.

But even the current Domino 9.0.1 FP4 version does not completely comply with ATS. DHE is supported in the current Domino FPs and can be configured which would be a vaild and good PFS cipher. But that is not on the ATS list.
There is currently no support for ECDHE in native Domino.

So I am interested to see the feedback from software companies on this Apple move.

On the other side there are Apple servers not complying to those standards and we are still having issues with some Apple SMTP Servers using SSLV2Hello.

It's going to be interesting again to see what will happen when a vendor like Apple pushes standards so hard and in such a short time.

IBM officially announced that they are working on a IF that will introduce ECDHE for all important internet protocols.

The timeline for the fix is end of September. So they will miss the very short timeline they had before iOS 9 will ship today by a couple of days.

-- Daniel



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