Subject: [Cfrg] Identity-based Crypto & Devices

From: Hannes Tschofenig <[email-masked]>
Date: Mon, 2 Nov 2015 08:18:10 +0100

Hi Akihiro,

I had a few questions during the meeting in context of your
presentation,
https://www.ietf.org/proceedings/94/slides/slides-94-cfrg-0.pdf, about
identity-based crypto on devices.

I wanted to repeat them on the mailing list:

a) What type of devices do you envision these mechanisms to be used?
Related to this is the question about performance? Is there some
performance data available?

b) What is the IPR status? Are you aware of IPRs on the presented scheme?

c) What are the main benefits compared to a classical PKI-based approach
where certificates are provisioned to devices during the manufacturing
process?

e) What are the key management you see with the devices? Slide #2
says "A management of credentials will be one of problem." but it does
not say what you believe the problem is. Asked differently, what problem
do you think needs to be solved that has not been solved by other
mechanisms previously?

It seems from the slide deck that you are claiming that the server
storage overhead for device credentials is less with identity-based
crypto than with a PKI-based approach. Could you be a bit more precise
about the number of bits that you optimize?

f) What are the disadvantages of the identity-based approach compared to
a pre-shared secret and the PKI-based approach? (Typically, there is a
tradeoff and you only presented the advantages.)

g) Could you tell us a bit about the background of your work? Are you
provisioning devices using the presented effort, you want to publish
research effort, or something else?

Ciao
Hannes

---

From: KATO Akihiro <[email-masked]>
Date: Tue, 10 Nov 2015 17:49:34 +0900

Hi Hannes,

Thank you for your question.
I'm going to  answer your question by in-line.

> performance data available?

We have implementations of BN-curve and Optimal Ate Pairing.
And there are some open source code of pairing;

Tepla : http://www.cipher.risk.tsukuba.ac.jp/tepla/index_e.html
Miracl: https://github.com/CertiVox/MIRACL

T. Unterluggauer and E. Wenger computed the run time of optimal ate paring
on an ARM Coretex-M0+ that is small and energy efficient microprocessor.
https://eprint.iacr.org/2014/800.pdf
By their result, optimal ate pairing's runtime  on Coretex-M0+ is 1 sec.

As next step of pairing, now we are coding open source FSU.
By Unterluggauer and Wenger's result, FSU's runtime is estimated about 4
sec on  Coretex-M0+.

> b) What is the IPR status? Are you aware of IPRs on the presented scheme?

We have the patent of FSU. And we are discussing the claim of the
intellectual property rights for the protocol of IETF. We offer the claim
of intellectual property rights for the ISO by an RAND.

> where certificates are provisioned to devices during the manufacturing

It's high-security! FSU has provable security for keeping secret session
key against following incidents:

1. KGC as trusted 3rd party is hijacked by malicious attacker and attacker
get KGC's secret key. FSU has master key forward security.

2. Random number generator is weak like the case of B-safe.

For epemeral random number leakage in other key exchange protocol,
attacker is able to get session key.

> about the number of bits that you optimize?

The problem on slide #2 is that it is hard to keep huge password
management because the number of passwords of N devices increases in
proportion to N.

As you pointed out, we can resolve password management problem with
PKI-Based approach.
But in PKI-Based case there are following troubles:
1. "Who generate secret and public key pair of IoT device."
2. "What is the process that issue certificate for authenticate of ID for
IoT device."

ID-Based approach resolve by following use case:
KGC generate secret keys for ID "#FACTORY-0001" to ID "#FACTORY-9999" and
send to the factory. Then the factory installs the key pair to each devices.

ID-Based approach can simplify key derivation operation.

> tradeoff and you only presented the advantages.)

The calculation cost and memory usage will take bigger than PKI-Based,
because FSU use the pairing.

> research effort, or something else?

Our background is "research background".
We invented the most secure id-based authenticated key exchange protocol FSU.
FSU is one of good primitive tool for secure IoT world with simple key
generation, password-less cryptography or weak RNG.
So we hope that you use FSU in the Internet world.

Please refer:

ISO/IEC 11770-3:2014 Information technology Security techniques Key
management Part 3: Mechanisms using asymmetric techniques.

Atsushi Fujioka, Fumitaka Hoshino, Tetsutaro Kobayashi, Koutarou Suzuki,
Berkant Ustaoglu, Kazuki Yoneyama: id-eCK Secure ID-Based Authenticated
Key Exchange on Symmetric and Asymmetric Pairing. IEICE Transactions
96-A(6): 1139-1155 (2013).

Regards.