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30 Sep, 4 tweets, 2 min read
The NSA guidelines for configuring VPNs continue to require IPsec for VPNs rather than WireGuard. I understand why this is (too much DJB cryptography in WireGuard) but IPsec is really a terrible mess of a protocol, which makes this bad advice. media.defense.gov/2020/Jul/02/20…
The number of footguns in IPsec is really high, and they mostly express themselves in terms of implementation errors in VPN devices/software. It’s these implementation errors that risk private data, not some abstract concern about cipher cryptanalysis.
To be clear, there’s nothing wrong with DJB cryptography. The problem here is that the NSA only approves a very specific list of algorithms (see attached) and that list hasn’t been updated since 2016. It doesn’t even list SHA-3 yet! cnss.gov/CNSS/openDoc.c…
I know folks will say this is a cheap shot, but it would also be nice if the DoD could figure out how to use non-USG certificate roots safely so this doesn’t happen…

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Matthew Green Profile picture
29 Sep
Everyone on HN is puzzling about how to ensure open access papers. The answer seems very simple: just have funding agencies (NSF/NIH/DARPA etc.) require a link to an Arxiv/ePrint version for each paper mentioned in an annual report.
For those who haven’t seen the current NSF system: for each paper you’ve published in a given year, you need to convert it into PDF/A (!!) and upload it to a private archival service run by the DoE, one that (I think) taxpayers can’t access.
(This PDF/A thing, as best I can tell, is just a subsidy for Adobe Creative Cloud. Every researcher I know converts their PDFs using a sketchy .ru website so that DoE server must be a haven of malware.)
Read 5 tweets
Matthew Green Profile picture
29 Sep
Ok I just want to follow this up with a sanity check: “Find My” uses Bluetooth, right? So keeping it active is *not* the same as simply powering the NFC chip, which I know was available in previous phones/OSes. Or is it?
I’m asking because I know that AirTags support NFC, but also Bluetooth. And maybe the NFC chipset also supports some kind of longer-range communications? Basic question is: does the phone application processor remain “on” to support this feature?
I like that Apple has made this feature so ubiquitous that its actual technical operation can be ignored. But I actually want to know what’s happening in my phone when it purports to be “turned off!”
Read 5 tweets
Matthew Green Profile picture
28 Sep
“iPhone Remains Findable After Power Off” what I can’t keep up anymore.
So I guess “power off” doesn’t mean “off” anymore, it means the device stays on and does some kind of low-power nearfield communication. I’m trying to decide how I feel about this.
The off switch is buried in the “Find My” settings dialog, weirdly in a tab called “Find My Network” which might make you think it’s intended to… find your network… but actually I think this is some kind of branding gone wrong. Image
Read 13 tweets
Matthew Green Profile picture
19 Sep
@claudiorlandi The claim that the protocol is “auditable.” This is a strong claim that is being made to consumers and politicians. What does it mean? I think it means “the pdata [first protocol message from server]” is a secure commitment to the scanning database X. 1/
@claudiorlandi In other words, under the assumption of *a malicious server* the clients can be assured that (provided they check that their pdata is what Apple intended to publish) then Apple cannot scan for items outside of a committed database. And this is (at least privately) verifiable. 2/
@claudiorlandi My first observation is that while this “auditability” property exists in Apple’s public claims, no corresponding “dishonest server” properties exist anywhere in the formal description of the protocol. Check for yourself. 3/
Read 9 tweets
Matthew Green Profile picture
17 Sep
So this indictment is puzzling. It concerns Michael Sussman, a lawyer who organized the collection of DNS data from hosting providers allegedly for political purposes. Many of the companies are anonymized, can we tell who they are? (Thread) context-cdn.washingtonpost.com/notes/prod/def…
So we begin with “Internet Company-1”, which is a (major?) DNS resolver. Image
The executive in question (Tech Executive-1) claims to have been offered a position as Hillary Clinton’s cyberczar if she won, so maybe that’s a clue? Image
Read 6 tweets
Matthew Green Profile picture
14 Sep
A lot of pro-CSAM scanning arguments take the following form: “phones already have lots of opportunities (real and potential) for privacy abuse, so you’re stupid for minding when we try to introduce a new and highly-scalable one.”
And to some extent this argument is correct! It’s hard to believe this, but the iPhone (and mass-market smartphones) only launched in 2007. In 14 short years these devices have done more to erode user privacy than 114 years of all other electronic technologies combined.
From my perspective the only reasonable reaction for any technologist observing this incredible privacy collapse is: to wake up in the morning trying to fix it, and collapse into bed at night having spent the entire day trying to undo the damage.
Read 8 tweets

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