Related to the bullet point above, the AAA server has access to the material necessary to derive the session key; thus, the AAA server can observe any traffic encrypted between the client and RP. This "feature" was chosen as a simplification and to make performance faster; if it was decided that this trade-off was not desirable for privacy and security reasons, then extensions to ABFAB that make use of techniques such as Diffie-Hellman key exchange would mitigate this.