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Chris Fenner

@chrisfenner.bsky.social
25 followers 20 following 45 posts
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Chris Fenner @chrisfenner.bsky.social · 14/03/2026
Yes, Seattle traded away Howard Schultz for a first round pick though
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Chris Fenner @chrisfenner.bsky.social · 13/03/2026
We brought PQC (beginning with ML-DSA and ML-KEM) to TPM 2.0! While it’s only been a year since we last published, the big changes needed for PQC have been in the works since 2022. This was a monumental team effort and I’m so proud of the team for getting it done!
trustedcomputinggroup.org
TPM 2.0 Library | Trusted Computing Group
TCG has released the TPM 2.0 Library specification that provides updates to the previous published TPM main specifications. The changes and enhancements compared to the existing TPM 1.2 include: Suppo...
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Chris Fenner @chrisfenner.bsky.social · 08/03/2026
I see “only supports RSA” and “TPM” on the same slide and I have Questions
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Chris Fenner @chrisfenner.bsky.social · 22/02/2026
We need more former bartenders in Standards groups too!
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Chris Fenner @chrisfenner.bsky.social · 18/02/2026
🙌 “Mistakes in cryptography are not a sin […]. They’re simply a fact of life. As somebody once said, “cryptography is nightmare magic math that cares what color pen you use.” We’re all going to get stuff wrong if we stick around long enough to do something interesting[.]”
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Chris Fenner @chrisfenner.bsky.social · 17/02/2026
M Night Shyamalan -ass security protocol
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Reposted by Chris Fenner
Filippo Valsorda @filippo.abyssdomain.expert · 16/02/2026
Frog and Toad with a box illustration. Badly edited text.

Frog put the KEY in a box. "There," he said. "Now we will not SIGN MALICIOUS MESSAGES."
"But we can ASK THE HSM," said Toad.
"That is true," said Frog.
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Chris Fenner @chrisfenner.bsky.social · 16/02/2026
www.mariowiki.com/P-Wing
mariowiki.com
P-Wing
The P-Wing is a special item that debuted in Super Mario Bros. 3. The "P" stands for "Paratroopa" or "Patapata". In that game, it enables infinite flight for Raccoon Mario and Tanooki Mario, broadly ...
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Reposted by Chris Fenner
Ken Jennings @kenjennings.bsky.social · 15/02/2026
I miss when you could post Brave Norman Rockwell Townsperson and the caption could be, like, “R.E.M was wrong to leave ‘Fretless’ off of Out of Time” instead of “The secret police should stop murdering people.”
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Chris Fenner @chrisfenner.bsky.social · 13/02/2026
“You wrote a presentation that the authors of RFC 9794 would criticize” might be the “you wrote some code that the authors of the Linux kernel style guide would criticize” of teaching crypto
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Chris Fenner @chrisfenner.bsky.social · 13/02/2026
You can really tell someone spent 3 years perfecting this “Terminology for Post-Quantum Traditional Hybrid Schemes”
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Chris Fenner @chrisfenner.bsky.social · 13/02/2026
> RFC 9794 > “The word "hybrid" is also used in cryptography to describe encryption schemes that combine asymmetric and symmetric algorithms [RFC9180], so using it in the post-quantum context overloads it and risks misunderstandings.” > Puts the word “hybrid” on everything
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Chris Fenner @chrisfenner.bsky.social · 10/02/2026
I finally reached the end. This was a super good episode and it gave me all the warm fuzzies about my internal reactions to getting started with Ossl3 for PQC. As a former windows NCrypt provider maintainer, I really thought all my “magic strings to throw at a generic API” was behind me 😭
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Chris Fenner @chrisfenner.bsky.social · 03/02/2026
6 more weeks of elliptic curve cryptography
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Chris Fenner @chrisfenner.bsky.social · 02/02/2026
just when I was learning to tolerate the EVP
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Chris Fenner @chrisfenner.bsky.social · 30/01/2026
Me several days ago: “why do all the ML-DSA signing test vectors have only up to 2 of ( key seeds, hedging randomness, and mu values )” Me now: “ok guess I’m sending a PR to Wycheproof
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Chris Fenner @chrisfenner.bsky.social · 29/01/2026
Oh 100%
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Chris Fenner @chrisfenner.bsky.social · 29/01/2026
I should clarify: “correctly implementing…”
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Chris Fenner @chrisfenner.bsky.social · 29/01/2026
Implementing a protocol that uses cryptography is harder than designing a protocol that uses cryptography. Normally I use that to explain to people that they need to minimize excessive complexity in their designs but imagine what designs the team responsible for this code is capable of
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Reposted by Chris Fenner
Some guy @internethuman.bsky.social · 27/01/2026
They believe in nothing. When you determine your views as being the midpoint between two opposing positions, it just shows that you don't hold actual beliefs or principles.
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Chris Fenner @chrisfenner.bsky.social · 27/01/2026
You found the logo for non-canonicalized EdDSA public keys
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Reposted by Chris Fenner
Olga Nesterova @onestpress.onestnetwork.com · 25/01/2026
Minnesota National Guard members have arrived at a federal building and were directed to distribute donuts, coffee, and hot chocolate to anti-ICE protesters. Guard members were issued reflective vests so they would not be mistaken for federal agents.
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Chris Fenner @chrisfenner.bsky.social · 24/01/2026
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Chris Fenner @chrisfenner.bsky.social · 24/01/2026
Pro tip: never design a policy-measurement scheme like this. It’s so brittle you will never be able to rotate keys. Imagine trying to bridge this system to PQC
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Chris Fenner @chrisfenner.bsky.social · 24/01/2026
This is why people reflexively dunk on BitLocker. As a product it is stuck on its threat model from the early 2000’s and Microsoft appears uninterested in modernizing it. But as Swift above, dunking is a bit less warranted in this case because escrow to 1 of N of your other devices is complex
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Chris Fenner @chrisfenner.bsky.social · 24/01/2026
So if you upgrade firmware and it’s signed by a different key that you already trusted, or the same keys you trusted before but used in a different order, PCR 7 will change and send BitLocker to recovery.
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Chris Fenner @chrisfenner.bsky.social · 24/01/2026
Here is the biggest problem I can see. PCR7 contains DB (authority keys and hashes) already but it gets extended again with each key the first time it gets used.
5. Before launching an EFI Driver or an EFI Boot Application (and regardless of whether the launch is due to the EFI Boot Manager picking an image from the DriverOrder or BootOrder UEFI variables or an already launched image calling the UEFI Loadlmage() function), the UEFI firmware SHALL determine if the entry in the EFI_IMAGE_SECURITY_DATABASE_GUID/EF|_ IMAGE_SECURITY_DATABASE variable that was used to validate the EFI image has previously been measured with the EV_EF_VARIABLE_AUTHORITY event type in PCR[7]. If it has not been, it MUST be measured into PCR[7] as follows. If it has been measured previously, it MUST NOT be measured again. The measurement SHALL occur in conjunction with image load.
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Chris Fenner @chrisfenner.bsky.social · 24/01/2026
Bonus lore: PCR7 measurements are badly designed partly at the behest of BitLocker ca. mid-2000’s. That problem cannot now be fixed except by updated standards: trustedcomputinggroup.org/wp-content/u...
trustedcomputinggroup.org
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Chris Fenner @chrisfenner.bsky.social · 24/01/2026
If you or a loved one are worried about the scenario where a corrupt government official is trying to get into your computer, you should disable online backup, print out the recovery keys, and put them in a box labeled “The Epstein Files”
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Chris Fenner @chrisfenner.bsky.social · 24/01/2026
If you’ve ever dug into the disaster that is the design of PCR7 measurements made by UEFI secure boot, you know how common BitLocker recovery has to be. Microsoft should invest in an Apple-like “escrow this key to your other devices” feature but this is a significant effort
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Chris Fenner @chrisfenner.bsky.social · 24/01/2026
It is fun and good to dunk on BitLocker not bothering to update their threat models (cf. TPM bus interposition) but Matthew’s thread breaks down how truly difficult Microsoft’s position is here — MS cannot serve remote recovery without also being technically able to respond to warrants
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Chris Fenner @chrisfenner.bsky.social · 17/01/2026
I am pleased to report that between HackerNews and Google’s internal “Learning on the Loo” program, I am officially published to toilets worldwide
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Chris Fenner @chrisfenner.bsky.social · 15/01/2026
The goal of getting the crypto right is for all your security bugs to be boring
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Reposted by Chris Fenner
Sharon 🪳🌹 @sharonk.bsky.social · 12/01/2026
it's incredible how if you put this entire dialog into the Left Behind series, it would basically work, but instead it's just IRL MN
"Sir! This is a warning!" the agent yelled as he punched the man's vehicle window. "Stop f—king following us! You are impeding operations! This is the United States federal government!"

"I live over here," the driver explained. "I got to get to my house."

"This is your warning!" the officer exclaimed.

"I serve the Lord; go to church," the resident replied.

"I will arrest you!" the officer threatened.

"Don't make a bad decision," another agent warned.

"I serve the Lord," the driver repeated. "Not a draft-dodging coward."

"Let these people go to church," the driver added. "Let these people serve the Lord and worship."

"You're not going to like the outcome of this, sir," the first officer said. "I guarantee that... Did you not learn from what just happened [when Renee Good was killed]?"

"Learn what?" the driver asked. "I serve the Lord, not a draft-dodging coward. I can't believe you'd take orders from a draft dodger."
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Chris Fenner @chrisfenner.bsky.social · 13/01/2026
I think the correct term for this is “end-to-middle-encrypted”
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Chris Fenner @chrisfenner.bsky.social · 13/01/2026
THOUGHTS IN PLAINTEXT
Archon from StarCraft, one of whose quotes was “Thoughts in Chaos” and for some reason I can remember that today but not what I was doing yesterday
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Chris Fenner @chrisfenner.bsky.social · 13/01/2026
Great news everyone, we found a way to 1,000,000x the number of GPUs everyone needs to buy from Jensen
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Chris Fenner @chrisfenner.bsky.social · 13/01/2026
As a user, I’m not impressed by E2E encryption where the other end is a device the hosting provider can spend $1000 to impersonate (tee.fail), also doesn’t the confidential VM need to transmit the prompt to e.g. six dozen GPUs?
tee.fail
TEE.fail: Breaking Trusted Execution Environments via DDR5 Memory Bus Interposition
Breaking Trusted Execution Environments via DDR5 Memory Bus Interposition
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Chris Fenner @chrisfenner.bsky.social · 13/01/2026
I don’t think the words “end to end encryption” belong in this post? confer.to/blog/2026/01...
confer.to
Private inference
When you use an AI service, you’re handing over your thoughts in plaintext. The operator stores them, trains on them, and–inevitably–will monetize them. You get a response; they get everything.
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Chris Fenner @chrisfenner.bsky.social · 10/01/2026
American Sturmabteilung
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Chris Fenner @chrisfenner.bsky.social · 08/01/2026
fell out of the [PQ large] tree hitting every branch on the way down
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Chris Fenner @chrisfenner.bsky.social · 07/01/2026
I’d like to pressure test the hypothesis that your only two choices are “email level security” and “if a motivated state actor can defeat it you failed”
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Chris Fenner @chrisfenner.bsky.social · 07/01/2026
Another thing that already works exactly like email is email
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Chris Fenner @chrisfenner.bsky.social · 04/01/2026
Yeah, I under-specified that part since the post was getting long. It depends on the hardware layout. You can “share” a TPM bus between a BMC and a CPU using a multiplexer, or you can have one device proxy the traffic for another.
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Chris Fenner @chrisfenner.bsky.social · 04/01/2026
I wrote about a feature I got disabled-by-default in Linux last year dlp.rip/decorative-c...
Jayne: “You know what the chain of trust is? It's the chain I go get and beat you with 'til ya understand who's trustin' who here.”
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Chris Fenner @chrisfenner.bsky.social · 15/10/2024
How have you liked working with No Starch as a writer?
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Chris Fenner @chrisfenner.bsky.social · 19/03/2024
The latest version of the TPM specification is out! And I’m really excited about it!
dlp.rip
Attesting to the TPM’s Firmware
Murphy’s Law says: Anything that can go wrong will go wrong. Unfortunately, TPMs fall into the category of “anything.”
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Chris Fenner @chrisfenner.bsky.social · 07/02/2024
Paging @mjg59.eicar-test-file.zip
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Chris Fenner @chrisfenner.bsky.social · 07/02/2024
dlp.rip
BitLocker is Designed to Have This Problem
The purpose of a system is what it does 1. The purpose of BitLocker is to generate articles about interposer attacks. sequenceDiagram participant host as Host system actor interposer as interposer par...
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