kfreds

15 ms·

151.
by kfreds 3y ago
> .. I wish there was some sort of black box mechanism for logging certain events in such a way that the device itself can't tamper with it.. This is called an append-only log. It can be built in many ways. Which way is suitable lar
152.
by kfreds 3y ago
Excellent question! The reason has to do with the fundamental differences between software and hardware. Think of software as fundamentally sequential and hardware as fundamentally parallel: Software source code can't run directly on h
153.
by kfreds 3y ago
Yes, that's correct. Thank you!
154.
by kfreds 3y ago
Yes. I've described some of the flexibility characteristics elsewhere in this thread, but here's how you could do it: 1. The ROM stage measures the first mutable application stage A1, and makes the Compound Device Identifier (CDI)
155.
by kfreds 3y ago
It's an excellent question to ask. We chose the CH552 in part due to the chip shortage at the time we locked in the design. According to the specification: It is effectively a USB PHY with a small microcontroller attached. Firmware upd
156.
by kfreds 3y ago
Thank you! We think so too. It is inspired by TCG DICE, which came out of Microsoft Research if I recall correctly. This approach has several other benefits as well (ownership transfer etc) which I've outlined in another comment in thi
157.
by kfreds 3y ago
If you really want to get into the details, effectively all modern CPU chips does have some firmware in ROM on-die. (I'm sure you know this but I'm writing it out here for the benefit of others) As the name Read-Only Memory implie
158.
by kfreds 3y ago
Thank you for the detailed response! Lots of good perspectives. Ryan Hurst is great. I ended up spending several hours with him at CCS talking about HSMs. I was mostly upstairs at CATS due to two other projects I'm involved with - Sigs
159.
by kfreds 3y ago
Thank you for your support! I'm pleased to hear you've been tinkering with it. We're working on FIDO2 and will get there one way or another. The current TKey uses CDC ACM as USB device class, which presents some compatibility
160.
by kfreds 3y ago
It depends on what you value. If you want a computer that can produce Ed25519 signatures with a minimum of software and hardware complexity and a maximum of inspectability then you probably can't do better than a TKey. Yubikey on the o
161.
by kfreds 3y ago
Yes. :)
162.
by kfreds 3y ago
Thank you! I absolutely what you've done with the Limited Edition Solo 2. The epoxy + nail polish and exposed PCB is a great artistic expression of the openness of the device. I appreciate the tip about the USB-C plug. As I recall we&#
163.
by kfreds 3y ago
The TKey enumerates as a CDC ACM (serial port) to the host, so I'm afraid it doesn't work on the Chromebook from what I can remember. My colleagues would know better. In any case it's something we aim to support one way or an
164.
by kfreds 3y ago
Thank you. Interesting paper! As you've already noted the TKey's KDF is Hash(UDS, Hash(TKey device app), USS), which means every device+application combination gets its own unique key material. As you conclude this means an update
165.
by kfreds 3y ago
Right. Speaking of which, do you have any recommendations for good USB cores?
166.
by kfreds 3y ago
It's a trade-off. We've thought about adding a screen to a future product, but it begs the question of how much information you want displayed in order to make your authentication decision. And even if a screen gives you more info
167.
by kfreds 3y ago
Same here. It was a source of inspiration when we started working on the TKey. Could you expand on what you mean by "take quite a bit of work". I thought Fomu came preconfigured?
168.
by kfreds 3y ago
To protect the UDS that we provision for you. See my other responses in this thread for more details. Also see the TKey Unlocked.
169.
by kfreds 3y ago
None. You'll simply have to trust that we have configured your TKey with a UDS of good entropy, and that we haven't saved it - intentionally or unintentionally. However, the device's flexibility allows you considerable contro
170.
by kfreds 3y ago
One major difference between TKey and Fomu is that Fomu uses the ice40 for USB hardware logic as well as USB device firmware. TKey uses a dedicated USB chip (CH552, which comes with open source firmware). Fomu could likely not fit USB logic
171.
by kfreds 3y ago
You're mostly correct. The immutable firmware derives unique key material for each device+application combination. However, nothing prevents the loaded application from loading another application. This allows the developer to construc
172.
by kfreds 3y ago
You're more than welcome to change the rules. Please read my other comments in this thread, and you'll hopefully find answers to your concerns. The TKey Unlocked gives you all the control you're asking for.
173.
by kfreds 3y ago
Regarding FIPS 140-2 level 2 tamper evidence and level 3 tamper response I'm interested to hear what you (and others here on HN) value and why. Level 2 can be accomplished with nail polish and glitter, or plastic potting. Yubikey'
174.
by kfreds 3y ago
I believe we already have a U2F prototype for Linux. In general we are quite selective about which applications we take on development and maintenance responsibilities for. Given that this is the most open source hardware USB authenticator
175.
by kfreds 3y ago
Sure. Specifically regarding not storing firmware: The TKey does have roughly 6 KB of immutable firmware which is responsible for loading device applications sent by the host. This firmware receives and then hashes the application together
176.
by kfreds 3y ago
The answer is, as always, it depends. I'll do my best to characterize the problem: If we only care about minimizing logic gates we could use SERV, the world's smallest RV32 core, and run a bare metal ECDSA implementation on it. Le
177.
by kfreds 3y ago
Whether TKey or Precursor is better depends on your needs. Here are some differences between them: * TKey uses open tooling for everything. Precursor uses Vivado. * Precursor has a screen and a keyboard, allowing the user to interact direct
178.
by kfreds 3y ago
FPGA: Lattice ice40up5k Toolchain: Yosys. For the convenience of most end users we configure and lock the FPGA. This allows them to start using it right away. The core cryptographic technology relies on a Unique per Device Secret (UDS). If
179.
by kfreds 3y ago
I created the TKey together with my colleagues. AMA. :)
180.
by kfreds 3y ago
For those interested, the underlying technology for this feature is transparency logs. Some technical details for iMessage's approach can be found here: https://security.apple.com/blog/imessage-contact-key-verific.

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