Matthew Green

I teach cryptography at Johns Hopkins. https://blog.cryptographyengineering.com (#matthew_d_green on the other site.)

Public Key

npub1tsr0tzpcqxta5h0mut3jj29ekmvzcck6crrqy566p8hpet26sgss5g4v4e

NIP-05 Address

matthew_d_green_at_ioc.exchange@mostr.pub

Profile Code

nprofile1qqs9cph43quqr976tha79cef9zumdkpvvtdvp3sz2ddqnmsu44dgyggpz4mhxue69uhhyetvv9ujumt0wd68ytnsw43qzxrhwden5te0wfjkccte9ehx7umhdpjhyefwvdhk6tj45n5

Publishing to

relay.mostr.pub

relay.noswhere.com

public.relaying.io

Author Public Key

npub1tsr0tzpcqxta5h0mut3jj29ekmvzcck6crrqy566p8hpet26sgss5g4v4e

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Last Notes

2024-09-10 13:01:08

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I’ve been trying to think about what privacy and government access look like in this very real, imminent world. And I can’t even get a handle on it to ask reasonable technical questions. But we ought to, because it’s coming. And it’s coming fast.

2024-08-15 00:19:22

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For ten seconds I thought about turning on Apple’s password manager, surely that’s the answer to this problem! Then I pictured my aunt making all her passwords “jydpaz-4ridvE-becbih” and my soul actually left my body for a minute.

2024-08-11 14:55:23

Do people who live in Europe ever have to grapple with this insanity? I’ll move tomorrow if the answer is “no”.
https://files.ioc.exchange/media_attachments/files/112/943/963/543/951/636/original/895916d02b65b520.jpeg

2024-08-07 11:29:30

Prediction markets seem to be really good at figuring out whatever widespread opinions are prevalent at any given moment, not so great at actually predicting things. Don’t know why people revere them so much.

2024-08-01 16:18:58

I am glad some of the “watermarking for LLMs” mania is dying down.

2024-07-21 18:06:28

Maybe one of the greatest Presidents we’ve ever had. I don’t usually do politics on social media anymore, but I have to say it.

2024-03-31 15:36:37

This thing Facebook did — running an MITM on Snapchat and other competitors’ TLS connections via their Onavo VPN — is so deeply messed up and evil that it completely changes my perspective on what that company is willing to do to its users.

2024-03-21 00:11:00

The weirdest thing about 2024 is the rapid rollout of unconstitutional age verification laws for websites, and how little the “free speech” tech crowd seems to care about this.

2024-03-20 15:26:31

The frequency with which ad-heavy pages crash iOS Safari doesn’t really fill me with confidence about the security of that browser.

2024-02-09 15:25:06

Makes the whole job worthwhile.
https://files.ioc.exchange/media_attachments/files/111/902/215/487/615/514/original/9c228810e9a5dafa.jpeg

2023-10-27 12:55:43

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This code is not cherry-picked. Every single line looks like this. It’s literally the most terrifying, unreadable pile of dogshit I’ve seen in my life. And as the owner of two dogs, I don’t use that term lightly.
https://files.ioc.exchange/media_attachments/files/111/307/085/465/634/223/original/9f2db0c98f074ded.jpeg

2023-10-27 12:54:56

A project my grad student is working on required us to review the implementation of the C++ standard library, and now I want to tear my eyes out.

2023-10-21 04:05:49

My daughter received an invitation for a Bar Mitzvah with a “World War II theme.” What am I supposed to do with this.

2023-10-18 11:42:59

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It’s amazing to me that a proposal to scan *literally ever private communication in Europe* is barely making newspapers, and we’re reading about legislative progress on blogs.

2023-10-18 11:29:17

The EU chat control legislation has been temporarily postponed. That’s good news. The bad news is there’s another vote in December. https://www.patrick-breyer.de/en/chat-control-vote-postponed-huge-success-in-defense-of-digital-privacy-of-correspondence/

2023-10-02 13:23:30

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But it’s an interesting technology demonstrating showing how much work there is to do in building efficient privacy-preserving protocols, and how little impact the research community has made on this problem after decades of work (sadly.)

2023-10-02 13:23:14

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Anyway it’s probably a good thing that none of this stuff got deployed. It was pretty rube-Goldbergian and not really clear what the entire point was.

2023-10-02 13:23:01

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I believe this was done by attaching a “serial number” to each individual certificates, where every serial number was derived from some chained pseudorandom function. You could publish a single “seed” to revoke every key in the chain. Gagh it was a nightmare.

2023-10-02 13:22:42

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Of course this still meant that revocation would be a nightmare. What do you do when you find a car’s signing keys have been stolen, how do you revoke thousands of keys at once?

2023-10-02 13:22:27

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Of course this still meant that the Certificate Authority would know the keys for every car. To avoid this, the CA would be split into two halves. One would receive the signing requests and verify they were ok, then it would shuffle them up and send them to be signed.

2023-10-02 13:22:12

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The basic idea IIRC was that every car would manufacture tens of thousands of independent signing keys, each of which would last a short time (maybe a day or less.) It would then get a certificate from a CA on every key. And it would use one at a time.

2023-10-02 13:21:55

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The folks involved in this idea looked at two decades of research cryptography, things like group and ring signatures and (IMHO rightly) decided that none of it was efficient enough. So instead they cooked up something else.

2023-10-02 13:21:39

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But all this data had to be authenticated, to keep bad guys from broadcasting false data and screwing up traffic. At the same time, the crypto used had to preserve *privacy* so you couldn’t use it to track cars. You also needed the ability to revoke signing authority.

2023-10-02 13:21:21

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The idea was that every car would constantly broadcast a message containing its GPS coordinates and speed, so every other car on the road would be able to do stuff like… I don’t really know. Avoid rear-ending other people? Also traffic lights and road signs would also broadcast.

2023-10-02 13:21:00

We don’t talk about it ever, but did you know the US built an entire “private” CA infrastructure for vehicle-to-vehicle communications and a few cars even launched with the capability, before everyone involved decided to scrap the idea?

2023-09-25 13:31:50

Do read this new investigatory piece on the web of money, AI companies, and shadowy “foundations” bankrolling the EU anti-encryption proposals. TL;DR this is the terrifying thing you get when you combine law enforcement, money and AI. https://balkaninsight.com/2023/09/25/who-benefits-inside-the-eus-fight-over-scanning-for-child-sex-content/

2023-09-24 17:24:49

I wonder who exactly is paying for the ads and what their specific business interests are.
https://files.ioc.exchange/media_attachments/files/111/121/287/419/253/892/original/75b29e33719493a6.png

2023-09-23 16:01:15

https://files.ioc.exchange/media_attachments/files/111/115/295/911/980/833/original/689a5f24e43e2966.jpeg
https://files.ioc.exchange/media_attachments/files/111/115/296/561/835/609/original/224cf80cf34128d0.mp4

2023-09-22 12:23:34

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Step 1: support two image formats. Step 2: if someone needs to send some weird image format to you, they convert it to one of the two formats that your phone’s formally-verified software can read.

2023-09-19 13:11:18

New leak from the Snowden archive.
https://files.ioc.exchange/media_attachments/files/111/091/978/932/359/373/original/c4b6ae1e8f0fa11f.png

2023-09-01 11:43:15

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@npub1x2u…3j8v What’s that a reference to?

2023-09-01 01:32:28

This article with quotes from Apple on why it killed the CSAM photo scanning initiative is the first thing I’ve seen from the company explaining their decision. https://www.wired.com/story/apple-csam-scanning-heat-initiative-letter/
https://files.ioc.exchange/media_attachments/files/110/987/309/453/405/699/original/50c84ba0b528e3c4.png
https://files.ioc.exchange/media_attachments/files/110/987/309/543/639/460/original/06d101fd76ed21d5.png

2023-09-01 01:31:26

It’s days like these you realize the human brain is a computer that runs on about five ounces of weird chemicals, and if you use it too much they all run out.

2023-08-23 16:54:38

Tornado cash founders have been charged with money laundering. https://www.justice.gov/usao-sdny/pr/tornado-cash-founders-charged-money-laundering-and-sanctions-violations

2023-08-22 05:22:38

I wrote a blog post about Worldcoin. https://blog.cryptographyengineering.com/2023/08/21/some-rough-impressions-of-worldcoin/

2023-08-17 02:46:29

Really wish this place had search.

2023-07-29 14:26:45

Some folks on HN were confidently asserting that Apple escrows its encryption keys with Chinese-government owned hosting providers “to facilitate mass surveillance.” This statement is messy because it’s 1/4-true, 1/4-false, 1/2 unknown. https://www.nytimes.com/2021/05/17/technology/apple-china-censorship-data.html?smid=nytcore-ios-share&referringSource=articleShare

2023-04-25 00:52:01

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If you had the most cynical possible view of humanity and its governments, you’d expect government agencies to be making a *huge* push to end encryption right now; or at least adorn it with mass-scanning infrastructure. And sure enough, that’s exactly what we’re seeing all around the world. https://www.globalencryption.org/2023/04/statement-on-eu-us-cooperation-against-encryption/

2023-04-25 00:49:50

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Many folks in law enforcement and politics seem genuinely confused about the popularity of end-to-end encrypted messaging, like we all just decided to become anarchists or something. That’s not at all the dynamic we’re seeing here. The entire basis of our communications infrastructure shifted in a direction that’s inimical to privacy; encryption is the obvious solution.

2023-04-25 00:44:39

It is remarkable to think that only in the past 15-20 years have we moved most of our private communications to digital channels with centralized storage & the processing power to perform bulk scanning. Coincidentally that’s nearly as long as encrypted messaging has been around.

2023-04-21 13:52:52

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I didn’t even want to share this experience because it was kind of embarrassing. Now imagine it had been CSAM. Nobody would have given the benefit of the doubt. Hell I probably wouldn’t have, if it was someone else.

2023-04-06 20:43:25

Let’s talk about this crazy East Coast April heat. Because this is really worrying me.

2023-04-05 01:37:44

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If you go to Settings/Wi-Fi/Edit and scroll to the bottom of a huge list, you do indeed see “managed” networks. Couldn’t be more obscure. Mine haven’t re-enabled yet so I can’t verify that part.
https://files.ioc.exchange/media_attachments/files/110/143/646/002/277/428/original/9b2dc6d796b52919.jpeg

2023-04-05 01:36:48

This HN post claims there are managed networks installed on iOS that can’t be disabled. Or more specifically: if you disable auto-join the setting will be overridden and turned back on after a while. https://news.ycombinator.com/item?id=35447486

2023-04-03 12:21:27

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May be redundant to say, but in a world with proper encryption and good key management: you could store your data anywhere you want and this never happens to you.

2023-04-03 12:20:37

I really don’t know why you’d store your data in a cloud operated by Western Digital. But if you did, you’re in trouble. https://www.bleepingcomputer.com/news/security/western-digital-discloses-network-breach-my-cloud-service-down/

2023-03-31 13:43:28

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And that’s what these models give, at almost unlimited scale. The ability to understand and monitor billions of people with all their complexity, at a super-human level of comprehension. And I’m not talking about tomorrow: the models we have today are good enough.

2023-03-31 13:15:33

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There’s an entire field of AI safety and ethics talking about disinformation. Who cares about disinformation? We’re not in any way short on that. So what if disinformation goes from $.02/tweet to $.0002/tweet. What we’re short on right now is *understanding*.

2023-03-31 13:13:39

We’re designing large language models with comprehension capabilities beyond anything computers have ever been capable of, and states are militating to put language models into your phone to scan private messages. It amazes me that we’re all so calm about this.

2023-03-07 13:40:40

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#[0] Yup.