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JackPair protects your privacy by encrypting your voice over phone calls.  It works with any device through standard 3.5 mm audio jack.
JackPair protects your privacy by encrypting your voice over phone calls. It works with any device through standard 3.5 mm audio jack.
303 backers pledged $44,661 to help bring this project to life.

Last Prototype, Mockup, Curve25519, and Detachable Design

Posted by Jeffrey Chang & the AWIT team (Creator)
1 like

Happy New Year! It’s been a while since our last update, and here’s our current status:

3rd & Last PCB Prototype Run

After our chip upgrade for the 2nd PCB prototype run, we were experiencing sporadic system instability issues; some of the boards had problems with peripherals like USB and OLED. After weeks of extensive diagnosis, we finally pinpointed the root causes; first, the crystal parts we were using had quality issues; we had to pick a new, high-quality crystal alternative and redesign the circuits around it to get consistent oscillations that meets our spec. We also have to redesign the charging circuit and replace working voltage from 3.0 volt to 3.3 volt. Another circuit change is the addition of dozens of test points for ICT at assembly line, which, together with bed-of-nails test fixtures, allows for automatic testing during mass production.

JackPair 3rd PCB prototype
JackPair 3rd PCB prototype

We had to wait for all the circuit re-designs and debuggings to be settled before producing our 3rd PCB prototype boards in December. We’re fortunate that our manufacturing partners worked with us closely for engineering changes in parts sourcing, and accommodate our tight schedules for PCB & SMT process. It was holiday season last month, and things were moving slower than we had expected. Thankfully, we had managed to finish our 3rd PCB prototype run right before Christmas, and now we’re busy testing our new board. There’s no surprise so far, and this should be our last prototype run.

ECDH: Curve25519

At first, we were not confident about Eclipse Curve because of its NIST background. However, people like Nicolai have communicated with us and pointed out that Curve25519 is a good choice for ECDH; DJB is the author of both Curve25519 and Salsa20, which is already used for JackPair. Curve25519 has really good performance with high security level, and is widely deployed by a lot of recent security projects. So we’ve decided to adopt Curve25519 as our Diffie-Hellman key exchange implementation.

Mechanical Design & Mockup

The Mechanical Design had been underway since our Industrial Design (of Concept #B) was selected back in October. Due to the circuit changes since our 2nd prototype, we were not able to finalize the Mechanical Design until early December, and then moved into the next step of building mockups before tooling. With cooperation from our manufacturing partners, our first mockup was finished literally at the last day of year 2014.  During New Year break, we have the first-hand experiences of playing around with the mockup, and are quite excited about its solid, modular design, which allows it to be assembled & detached easily.

JackPair Mockup
JackPair Mockup


At this point, we are striving to stick with our shipment schedule of March 2015. Our original schedule calls for tooling at December and January; however, due to delay in PCB & Mockup, the schedule for tooling is now moved to January and February, followed by mass-production and shipment in March 2015 as planed.  We’ve spent time on searching qualified mold and plastic injection vendors and now work with them closely; hopefully the tooling jobs can be done ahead of time, which allow us more room for production & shipment.

Detachable Design

The current mechanical design of JackPair makes use of Ultrasonic Welding to glue the 2 U-shaped outer parts together, which hold all components as one device. We are contemplating whether it makes sense to allow JackPair users to detach and re-assemble all the plastic components easily. This could be an extra feature in terms of security; it enables users of JackPair to examine what’s inside the device, by taking apart all the components of JackPair easily and verify that there’s no tampering or unexpected changes inside the device.

JackPair 3D transparent model
JackPair 3D transparent model

We wanna hear what you think about whether JackPair should be shipped with the plastic components sealed or not; does it make JackPair more secure if you can disassemble and reassemble the plastic parts of JackPair?  One of the negative issues we can think of is about product warranty: how do we make sure the product is in its original condition, especially the electronic parts, in order to honor our warranty service?  Let us know what you think by leaving a message publicly here or on facebook, or drop me an email privately.

Your feedback is appreciated here.


--- Jeffrey

Robbie Jeo likes this update.


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    1. Missing avatar

      mrsmith on

      I like the option (whether I would personally use it or not) to access the internals to verify the contents and/or replace the battery. As already mentioned, small tamper evident stickers could be a good way to indicate when the case has been opened for any reason.

      Thanks for all your hard work, and Happy New Year.

    2. Missing avatar

      Carl Watson on

      Just had a further thought you could make the 2 halves of the enclosure slot together along the long edges this could be incorporated into the case moulding and allow a single screw to be used to keep them from sliding open minimising assembly time and costs

    3. Missing avatar

      Carl Watson on

      I would definitely welcome being able to open the device from the point of view of changing the battery when needed, the lifespan of a battery is generally a lot less than the life of a device so sealing it is effectively reducing its usable lifespan.
      From the warranty point of view a good compromise is to use security screws that require a tri-lobal screwdriver to minimise the people who can physically open them, you could also use a non peelable warranty sticker over one of the screw holes to make tampering evident both for warranty purposes and for users to ensure their device hasn't been tampered with

    4. Missing avatar

      Tom Stevens on

      I don't think the ability to disassemble is worth the increased cost, but I really like the idea of a transparent plastic shell.

    5. Markus Fix

      I regularly secure electronics by "potting" it in silicone. Provides some protection in harsh environments (marine and tropical climates) and is hard to tamper with.

    6. Missing avatar

      Giovanni Civardi on

      Congratulations! I really appreciate your choice of using Curve25519 :)
      For the case: please, don't solder it, use screws instead. I Really hate devices which can't be opened/closed without breaking them...