Subject: [TLS] AES and CBC

From: "Sean Lawless" <[email-masked]>
Date: Mon, 19 Sep 2005 12:20:08 -0700

Greetings,

I'm looking for details about the AES CBC settings for TLS;
TLS_RSA_WITH_AES_256_CBC_SHA and TLS_RSA_WITH_AES_128_CBC_SHA.  RFC 3268
describes little detail.

How does AES for TLS differ from RFC 3602 (AES with IPsec)?  Are the AES
Number of Rounds dependent upon the key size?

Regards,

------------------------------------------------------------
Sean Lawless, Senior Software Engineer
Blunk Microsystems
[email-masked]
www.blunkmicro.com
------------------------------------------------------------ 

_______________________________________________
TLS mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/tls

---

From: Tim Dierks <[email-masked]>
Date: Mon, 19 Sep 2005 16:57:54 -0400

> Number of Rounds dependent upon the key size?

The AES used is the AES standard, so yes, rounds are depedent on key
size. All such details are defined as part of AES, not as part of
protocol standards that use it (such as IPsec or TLS).

Without looking in detail, I imagine that the big differences between
TLS & IPsec's use of AES will be chaining mode (unless both are CBC),
IV derivation, and padding. Then the use within the protocol is
different (i.e., MAC location & generation). Of course, keying, etc.
are entirely different.

 - Tim