david wong

Hey! I'm David, the author of the Real-World Cryptography book. I'm a crypto engineer at O(1) Labs on the Mina cryptocurrency, previously I was the security lead for Diem (formerly Libra) at Novi (Facebook), and a security consultant for the Cryptography Services of NCC Group. This is my blog about cryptography and security and other related topics that I find interesting.

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Pretty diagrams with Tikz in LaTeX posted March 2015

Because studying Cryptography is also about using LaTeX, it's nice to spend a bit of time understanding how to make pretty documents. Because, you know, it's nicer to read.

Here's an awesome quick introduction of Tikz that allows to make beautiful diagram with great precision in a short time:

And I'm bookmarking one more that seems go way further.

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GPS tracking device in real life! posted March 2015

I've only seen that in movies. Not that it couldn't exist, it's just "fun" to see that happen in real life as well.

The story is here. It's about someone's car which got "bugged". It was discovered while X was at the Circumvention Tech Festival in Valencia, Spain.

bug

more pictures there

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Funny matasano job post posted March 2015

I stumbled on this funny job post from jeff jarmoc:

This thread will, no doubt, be dominated by posts with laundry lists of requirements. Many employers will introduce themselves by describing what they want from you. At Matasano, we're a little different. We like to start by telling you about us. This month, I want to try to do that by drawing analogy to Mission Impossible.
What made the original show so great is exactly what was lost in the 'Tom Cruise takes on the world' reboot. The original 1960's and 70's Mission Impossible was defined primarily by a team working together against all odds to achieve their objective. It acknowledged that what they were doing was improbable, and more so for a solo James Bond or Tom Cruise character. As a team though, each character an expert in their particular focus area, the incredible became credible -- the impossible, possible.

the rest is here: https://news.ycombinator.com/item?id=9127813

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Freak Attack posted March 2015

If you're up to date on crypto news you will tell me I'm slow. But here it is, my favorite explanation of the recent Freak Attack is the one from Matthew Green here

TLS uses a cipher suite during the handshake so that old machines can still chat with new machines that use new protocols. In this list of ciphers there is one called "export suite" that is a 512bits RSA public key. It was made by the government back then to spy on foreigners since 512bits is "easy" to factor. The vulnerability comes from the fact that you can still ask a server to use that 512bits public key (even though it should have been removed a long time ago). This allows you to make a man in the middle attack where you don't have to possess a spoofed certificate. You can just change the cipher request of the client during the handshake so that he would ask for that 512bits key. 36% of the servers out there would accept that and reply with such a key. From here if we are in the middle we can just factor the key and use that to generate our own private key and see all the following exchange in clear.

More info here

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