I am in favor of the switch back to draft-13 key derivations.
Jorge Vergara
From: Emu <emu-boun...@ietf.org> On Behalf Of Joseph Salowey
Sent: Sunday, May 9, 2021 10:54 AM
To: EMU WG <emu@ietf.org>
Subject: [Emu] Consensus call on EAP-TLS key derivation
We had discussion on the list on whether to include context in the key
derivation, but we never closed on the issue of separating out the MSK and EMSK
derivation. As a result several implementers have gone down the path of
implementing what is in draft 13 and not separating out the derivation. The
main difference is that draft 15 separated out the EMSK and MSK derivation
using two different labels while draft 13 used a single label to derive key
material which is partitioned into two keys. The reason for the change was to
enable different access control for these two different quantities for
different callers, however in practice it is EAP-TLS application which needs
access to both keys that is the caller of the TLS library so this separation is
not particularly useful. Therefore the recommendation is to align with
implementation and derive the MSK and EMSK by partitioning the key material
from the key material produced by a single label of the exporter function.
Please respond to the list if you support the change below or not to revert
some of the text in the key derivation section. If you object to the change
please state why. Please respond by May 20,2021.
Thanks,
Joe
The proposal is to use the following key derivation which is largely a
reversion to draft 13:
Draft-15 Text:
Type-Code = 0x0D
MSK = TLS-Exporter("EXPORTER_EAP_TLS_MSK",Type-Code,64)
EMSK = TLS-Exporter("EXPORTER_EAP_TLS_EMSK",Type-Code,64)
Method-Id = TLS-Exporter("EXPORTER_EAP_TLS_Method-Id",Type-Code,64)
Session-Id = Type-Code || Method-Id
Proposed New Text:
Type-Code = 0x0D
Key_Material = TLS-Exporter("EXPORTER_EAP_TLS_Key_Material",
Type-Code, 128)
MSK = Key_Material(0, 63)
EMSK = Key_Material(64, 127)
Method-Id = TLS-Exporter("EXPORTER_EAP_TLS_Method-Id",
Type-Code, 64)
Session-Id = Type-Code || Method-Id
The rest of the text of the section remains the same as draft-15.
_______________________________________________
Emu mailing list
Emu@ietf.org
https://www.ietf.org/mailman/listinfo/emu
