Subject: [sfc] A proposal for ordered proof of transit

From: "Diego R. Lopez" <[email-masked]>
Date: Sat, 14 Jul 2018 19:30:27 +0000

Hi,

You’ll probably have seen the item of the proposal for ordered proof of transit (OPOT) in the Montreal agenda. We have come with a proposal that we think satisfies the two essential requirements of having a reasonable computational cost and to be compatible with the mechanisms described in the POT draft. In fact, our proposal would be to update the draft with the following procedure:

8<

OPOT Procedure

1. The controller provisions all the nodes with (or asks them to agree on)
a couple of secrets, that we will refer as masks, one for the upstream link,
another for the downstream link. For obvious reasons, the ingress and
egress (verifier) nodes only receive one, for downstream and upstream,
respectively.

2. Any two contiguous nodes in the OPOT stream share the mask for the
link connecting them, in the shape of symmetric keys. Masks can be
refreshed as per-policy, defined at each hop or globally by the controller

3. Each mask has the same size in bits as the length assigned to CML plus
RND, as described above.

4. Whenever a packet is received at an intermediate node, the
CML+RND sequence is deciphered (XOR SHOULD be applied for this) with
the upstream mask before applying the procedures described in 3.3.2.

5. Once the new values of CML+RND are produced, they are ciphered
(XOR SHOULD be applied for this) with the downstream mask before
transmitting the packet to the next node downstream.

6. The ingress node only applies step 5 above, while the verifier
only applies step 4 before running the verification procedure.

The described process allows the verifier to check if the packet has
followed the correct order while traversing the path. In particular,
the reconstruction process will fail if the order is not respected, as
the deciphering process will produce invalid CML and RND values, and
the interpolation (secret reconstruction) will finally generate a wrong
verification value.

>8

For sure we will need to include additional considerations and update accordingly some sections in the draft, and we’d like to proceed in that direction  if the WG thinks this is a worthwhile way to go.

Be goode,

--
"Esta vez no fallaremos, Doctor Infierno"

Dr Diego R. Lopez
Telefonica I+D
https://www.linkedin.com/in/dr2lopez/

e-mail: [email-masked]<mailto:[email-masked]>
Tel:         +34 913 129 041
Mobile:  +34 682 051 091
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