[openssl-dev] ECDH engine

Blumenthal, Uri - 0553 - MITLL uri at ll.mit.edu
Wed Jan 20 18:02:18 UTC 2016


I forgot to add that ‎OpenSSL-1_0-2-stable with the current (Github master) engine-pkcs11, libp11, and OpenSC successfully does ECDSA with keys on the token (tested for ECC256 and ECC384).

OpenSC tools successfully derive (i.e., implement ECDH1_DERIVE). I'm waiting for libp11 and engine_pkcs11 to add this capability.

Ideally this is where your code would plug in, and complete the circle.

As it currently is, a separate Atmel-specific ECC-specific engine is of a limited usefulness.

Sent from my BlackBerry 10 smartphone on the Verizon Wireless 4G LTE network.
From: Blumenthal, Uri - 0553 - MITLL
Sent: Wednesday, January 20, 2016 12:46
To: openssl-dev at openssl.org
Reply To: openssl-dev at openssl.org
Subject: Re: [openssl-dev] ECDH engine

The ATECC508A is a chip. There are few USB devices built by Atmel on its base. Or you can use the chip directly over I2C (that many people like to do). You can follow the links that we posted on the ATECCX08 Engine repository WiKi to learn about the chip. 

I see, thanks.

Well, our first indent was to use the pksc11 library. But it didn't go to well for many reasons. I should go back for several months to collect these reasons but I think the main reason was that ATECC508A hardware is based on ECC-256 algorithms while pkcs11 is originally written for RSA - the overhead was looking too high (many ATECC508 customers are using limited hardware and want direct I2C connection to the chip). 

There are a few hardware tokens (USB-pluggable), e.g. Yubikey, that support ECC256 and (in case of Yubikey 4) ECC384.

But let's talk about pkcs11. Can you point me to the set of documentation for EC-DERIVE? It may be a good time now to add the ATECC508 support to there.

Honestly, I’m more interested in adding ECDH support – assuming that it would also serve ATECC508, rather than working on ATECC508B and hoping that perhaps it would be usable for other ECC-capable tokens.

Here’s the PKCS#11 spec http://docs.oasis-open.org/pkcs11/pkcs11-curr/v2.40/pkcs11-curr-v2.40.pdf, which covers ECDH including ECDH1_DERIVE and ECDH1_COFACTOR_DERIVE. I think older versions (like v2.20) have more content, but this is the current one.

Hope it helps.

P.S. At this time I’m standing by my original opinion – that a better way is incorporating ECDH1_*DERIVE in libp11 and engine_pkcs11, rather than creating an engine specifically for one chip that add uncertainly of non-interoperability with other chips/tokens.


On Jan 20, 2016, at 8:11 AM, Blumenthal, Uri - 0553 - MITLL <uri at ll.mit.edu> wrote:

What is this Atmel x508x? Is it a chip? Is it a token/smartcard? Is it accessible via PKCS#11 at all? Is it accessible by/via OpenSC?

I am trying to figure why such a generic and useful set of ECC operations (Sign, Derive) is implementation-limited to one single <whatever>. 

A much better solution to me would be adding EC-DERIVE to engine_pkcs11, and automatically get all the tokens covered.

Since I'm probably‎ missing something, could you please educate me?

Sent from my BlackBerry 10 smartphone on the Verizon Wireless 4G LTE network.
From: Alexander Gostrer‎
Sent: Wednesday, January 20, 2016 10:47
To: Dr. Stephen Henson
Reply To: openssl-dev at openssl.org
Cc: openssl-dev at openssl.org
Subject: Re: [openssl-dev] ECDH engine
‎
Hi Steve,
‎
And here is the ENGINE implementation for Atmel ATECC508A with few small patches to OpenSSL_1_0_2-stable:
https://github.com/AtmelCSO/cryptoauth-openssl-engine

Your comments are welcome.

Regards,
Alex.

On Sat, Dec 19, 2015 at 12:49 PM, Dr. Stephen Henson <steve at openssl.org> wrote:
On Fri, Dec 18, 2015, Alexander Gostrer wrote:

> Hi Steve,
>
> John and I completed writing an ECDH engine based on the
> OpenSSL_1_0_2-stable branch. We were planning to expand it to the master
> but found some major changes made by you recently. What is the status of
> this task? Is it stable enough to follow it? Are you planning another
> changes? Is there a design document that we can use in our work?
>

The version in master shouldn't change much any more. Documentation will be
available in the near future. The changes were meant to remove some of the
weird "quirks" of ECC compared to other algortihms and to permit future
expansion to a wider range of curves.

In the meantime it shouldn't be too hard to follow how the new code works.
Instead of separate ECDH/ECDSA methods with weird locking and ex_data and
minimal ENGINE support everything is combined into a single EC_KEY_METHOD
which can contain ECDSA, ECDH and key generation (something which was
impossible with the old code) and be tied directly to an ENGINE.

Most of the primary APIs such as ECDH_compute_key can be redirected directly
through an engine supplied function in EC_KEY_METHOD.

Having said that the code is very new and may have the odd bug that needs to
be fixed. If you have any problems let me know and I'll look into them.

Steve.
--
Dr Stephen N. Henson. OpenSSL project core developer.
Commercial tech support now available see: http://www.openssl.org


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