Chris Peikert
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chrispeikert.bsky.social
Chris Peikert
@chrispeikert.bsky.social
500 followers 34 following 96 posts
Cryptographer (lattices/post-quantum), Professor at U-Michigan Computer Science and Engineering , Head of Cryptography Research at Algorand, PhD from MIT CSAIL. Previously faculty at Georgia Tech School of CS. Here I speak for myself.
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Reposted by Chris Peikert
chrislhayes.bsky.social
Also, maybe we come up with, like, two more holidays, say in the early and late spring, that involve walking around the neighborhood and talking to your neighbors?
October 31, 2025 at 10:56 PM
Reposted by Chris Peikert
radleybalko.bsky.social
This is ugly. But the reason this lady was protesting is even worse. ICE thugs detained two children and their father on their way to school. One child appears to have been beaten in detention, and no one seems to know where the 12-year-old girl is right now. The family had been seeking asylum.
Shock Video Shows ICE Agent Assaulting Woman Who Asked If He’s A Good Christian
Hundreds protested Tuesday at an ICE facility in southwest Colorado after agents detained two children on their way to school.
www.huffpost.com
October 29, 2025 at 10:00 PM
chrispeikert.bsky.social
and of my research pathway
gbodwin.bsky.social Greg Bodwin @gbodwin.bsky.social · 14d
this is a pretty accurate summary of my research area
October 28, 2025 at 3:05 PM
Reposted by Chris Peikert
normative.bsky.social
Must have taken a wrong turn on the way to the “Hate America rally”; all I see are American flags & signs promoting the Constitution, liberty, & democracy.
No kings protest in DC
October 18, 2025 at 4:19 PM
chrispeikert.bsky.social
We’re thrilled to receive a Distinguished Paper Award for this work!

www.sigsac.org/ccs/CCS2025/...
October 16, 2025 at 11:19 AM
chrispeikert.bsky.social
⚡New paper⚡, with Guy Zyskind, Doron Zarchy, and Max Leibovich of Fhenix, presented today at ACM CCS.

We give an efficient 𝒕𝒉𝒓𝒆𝒔𝒉𝒐𝒍𝒅 𝒅𝒆𝒄𝒓𝒚𝒑𝒕𝒊𝒐𝒏 protocol for FHE/LWE with: no "noise flooding" or parameter loss, simulation (UC) security, and high throughput.

web.eecs.umich.edu/~cpeikert/pu...
Title: High-Throughput Universally Composable Threshold FHE Decryption by Guy Zyskind, Doron Zarchy, Max Leibovich, and Chris Peikert Threshold Fully Homomorphic Encryption (FHE) enables arbitrary computation on encrypted data, while distributing the decryption capability across multiple parties. A primary application of interest is low-communication multi-party computation (MPC), which benefits from a fast and secure threshold FHE decryption protocol. Several works have addressed this problem, but all existing solutions rely on "noise flooding" for security. This incurs significant overhead and necessitates large parameters in practice, making it unsuitable for many real-world deployments. Some constructions have somewhat better efficiency, but at the cost of weaker, non-simulation-based security definitions, which limits their usability and composability. In this work, we propose a novel threshold FHE decryption protocol that avoids "noise flooding" altogether, and provides simulation-based security. Rather than masking the underlying ciphertext noise, our technique securely removes it via an efficient MPC rounding procedure. The cost of this MPC is mitigated by an offline/online design that preprocesses special gates for secure comparisons in the offline phase, and has low communication and computation in the online phase. This approach is of independent interest, and should also benefit other MPC protocols (e.g., secure machine learning) that make heavy use of non-linear comparison operations. We prove our protocol secure in the Universal Composability (UC) framework, and it can be generally instantiated for a variety of adversary models (e.g., security-with-abort against a dishonest majority, or guaranteed output delivery with honest majority). Compared to the state of the art, our protocol offers significant gains both in the adversary model (i.e., dishonest vs. honest majority) and practical performance: empirically, our online phase obtains approximately 20,000x better throughput, and up to a 37x improvement in latency.
October 14, 2025 at 3:40 PM
chrispeikert.bsky.social
⚡New paper⚡, with Alexandra Veliche Hostetler!

We give a list-decoding algorithm for Reed-Solomon codes, where the error is measured in the Euclidean (ℓ₂) or Lee (ℓ₁) metrics, rather than the Hamming metric (as is more typical).

web.eecs.umich.edu/~cpeikert/pu...
Title: List Decoding Reed--Solomon Codes in the Lee, Euclidean, and Other Metrics Abstract: Reed--Solomon error-correcting codes are ubiquitous across computer science and information theory, with applications in cryptography, computational complexity, communication and storage systems, and more. Most works on efficient error correction for these codes, like the celebrated Berlekamp--Welch unique decoder and the (Guruswami--)Sudan list decoders, are focused on measuring error in the Hamming metric, which simply counts the number of corrupted codeword symbols. However, for some applications, other metrics that depend on the specific values of the errors may be more appropriate. This work gives a polynomial-time algorithm that list decodes (generalized) Reed--Solomon codes over prime fields in $\ell_p$ (semi)metrics, for any $0 < p \leq 2$. Compared to prior algorithms for the Lee ($\ell_1$) and Euclidean ($\ell_2$) metrics, ours decodes to arbitrarily large distances (for correspondingly small rates), and has better distance-rate tradeoffs for all decoding distances above some moderate thresholds. We also prove lower bounds on the $\ell_{1}$ and $\ell_{2}$ minimum distances of a certain natural subclass of GRS codes, which establishes that our list decoder is actually a unique decoder for many parameters of interest. Finally, we analyze our algorithm's performance under *random* Laplacian and Gaussian errors, and show that it supports even larger rates than for corresponding amounts of worst-case error in $\ell_{1}$ and $\ell_{2}$ (respectively).
October 13, 2025 at 2:53 PM
chrispeikert.bsky.social
This was an hour ago!
chrislhayes.bsky.social Chris Hayes @chrislhayes.bsky.social · Oct 11
This game is deranged.
October 11, 2025 at 5:05 AM
Reposted by Chris Peikert
jameeljaffer.bsky.social
MIT's response to the Trump admin's proposed "compact" is excellent and should be a model for other universities. orgchart.mit.edu/letters/rega...
October 10, 2025 at 2:14 PM
Reposted by Chris Peikert
eprint.ing.bot
FrodoKEM: A CCA-Secure Learning With Errors Key Encapsulation Mechanism (Lewis Glabush, Patrick Longa, Michael Naehrig, Chris Peikert, Douglas Stebila, Fernando Virdia) ia.cr/2025/1861
Abstract. Large-scale quantum computers capable of implementing Shor’s algorithm pose a significant threat to the security of the most widely used public-key cryptographic schemes. This risk has motivated substantial efforts by standards bodies and government agencies to identify and standardize quantum-safe cryptographic systems. Among the proposed solutions, lattice-based cryptography has emerged as the foundation for some of the most promising protocols. This paper describes FrodoKEM, a family of conservative key-encapsulation mechanisms (KEMs) whose security is based on generic, “unstructured” lattices. FrodoKEM is proposed as an alternative to the more efficient lattice schemes that utilize algebraically structured lattices, such as the recently standardized ML-KEM scheme. By relying on generic lattices, FrodoKEM minimizes the potential for future attacks that exploit algebraic structures while enabling simple and compact implementations. Our plain C implementations demonstrate that, despite its conservative design and parameterization, FrodoKEM remains practical. For instance, the full protocol at NIST security level 1 runs in approximately 0.97 ms on a server-class processor, and 4.98 ms on a smartphone-class processor. FrodoKEM obtains (single-target) IND-CCA security using a variant of the Fujisaki-Okamoto transform, applied to an underlying public-key encryption scheme called FrodoPKE. In addition, using a new tool called the Salted Fujisaki-Okamoto (SFO) transform, FrodoKEM is also shown to tightly achieve multi-target security, without increasing the FrodoPKE message length and with a negligible performance impact, based on the multi-target IND-CPA security of FrodoPKE. Image showing part 2 of abstract.
October 8, 2025 at 4:55 AM
Reposted by Chris Peikert
juddlegum.bsky.social
1. Federal agents from ICE and other agencies are wrongly detaining U.S. citizens, sometimes detaining them for days, on suspicion that they are undocumented immigrants.

The raids are done without search warrants or other procedures designed to protect civil liberties.
How federal agents are terrorizing American citizens
Last week, hundreds of heavily armed federal agents descended on an apartment complex in Chicago, arriving in Black Hawk helicopters and moving trucks.
popular.info
October 6, 2025 at 1:17 PM
Reposted by Chris Peikert
kristinacooke.bsky.social
I spoke to a Venezuelan woman who was arrested in this raid and later released with her 4yo son. She said agents broke down their door, pointed guns at them and made sexualized remarks about Venezuelan women. When she returned to her apartment it was boarded up and all her possessions were gone.
October 4, 2025 at 2:30 PM
Reposted by Chris Peikert
govpritzker.illinois.gov
This morning, the Trump Administration’s Department of War gave me an ultimatum: call up your troops, or we will. It is absolutely outrageous and un-American to demand a Governor send military troops within our own borders and against our will.
October 4, 2025 at 6:10 PM
Reposted by Chris Peikert
govpritzker.illinois.gov
Yesterday, Kristi Noem’s and Greg Bovino’s masked agents threw chemical agents near an elementary school, arrested elected officials exercising their First Amendment rights, and raided a Wal-Mart.
October 4, 2025 at 6:10 PM
Reposted by Chris Peikert
eprint.ing.bot
High-Throughput Universally Composable Threshold FHE Decryption (Guy Zyskind, Doron Zarchy, Max Leibovich, Chris Peikert) ia.cr/2025/1781
Abstract. Threshold Fully Homomorphic Encryption (FHE) enables arbitrary computation on encrypted data, while distributing the decryption capability across multiple parties. A primary application of interest is low-communication multi-party computation (MPC), which benefits from a fast and secure threshold FHE decryption protocol. Several works have addressed this problem, but all existing solutions rely on “noise flooding” for security. This incurs significant overhead and necessitates large parameters in practice, making it unsuitable for many real-world deployments. Some constructions have somewhat better efficiency, but at the cost of weaker, non-simulation-based security definitions, which limits their usability and composability. In this work, we propose a novel threshold FHE decryption protocol that avoids “noise flooding” altogether, and provides simulation-based security. Rather than masking the underlying ciphertext noise, our technique securely removes it via an efficient MPC rounding procedure. The cost of this MPC is mitigated by an offline/online design that preprocesses special gates for secure comparisons in the offline phase, and has low communication and computation in the online phase. This approach is of independent interest, and should also benefit other MPC protocols (e.g., secure machine learning) that make heavy use of non-linear comparison operations. We prove our protocol secure in the Universal Composability (UC) framework, and it can be generally instantiated for a variety of adversary models (e.g., security-with-abort against a dishonest majority, or guaranteed output delivery with honest majority). Compared to the state of the art, our protocol offers significant gains both in the adversary model (i.e., dishonest vs. honest majority) and practical performance: empirically, our online phase obtains approximately 20,000× better throughput, and up to a 37× improvement in latency. Image showing part 2 of abstract.
October 3, 2025 at 7:24 AM
Reposted by Chris Peikert
chrispeikert.bsky.social
We will Make this deadline, very strongly, because we are WINNERS—but Europe and the Rest of the world will have to pay up BIGLY with the strongest and Most polished Best Paper awards! That is the least these low IQ individuals can do to Pay back what we Americans so richly deserve!
October 3, 2025 at 3:37 AM
chrispeikert.bsky.social
Other countries in Europe are LAUGHING at us, with their “Midnight Anywhere on Earth” conference submission Deadlines!!

They’re finishing their papers and taking off for the Weekend at 2pm Friday, while we Americans have to pull ALL-NIGHTERS!

Not on my (your favorite PC chair) watch—MAGTBAARHA!
October 3, 2025 at 12:14 AM
Reposted by Chris Peikert
sorenspicknall.bsky.social
"Rodrick Johnson, 67, is one of many residents who were detained by federal agents during the South Shore raid. A U.S. citizen, he said agents broke through his door and dragged him out in zip ties."
Massive immigration raid on Chicago apartment building leaves residents reeling: 'I feel defeated'
The Department of Homeland Security said federal agents with Border Patrol, the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives arrested 37 people in the raid.
chicago.suntimes.com
October 2, 2025 at 3:14 AM
Reposted by Chris Peikert
eprint.ing.bot
Vive Galois! Part 1: Optimal SIMD Packing and Packed Bootstrapping for FHE (Chris Peikert, Zachary Pepin) ia.cr/2025/1760
Abstract. The vast majority of work on the efficiency of lattice-based cryptography, including fully homomorphic encryption~(FHE), has relied on cyclotomic number fields and rings. This is because cyclotomics offer a wide variety of benefits, including good geometrical properties, fast ring arithmetic, and rich homomorphic operations like vectorized (SIMD) operations on “packed” plaintexts, automorphisms, and ring-switching. However, selecting a suitable cyclotomic that has the desired number and type of plaintext “slots,” while also balancing security and efficiency, is a highly constrained problem that often lacks an ideal solution, resulting in wasted SIMD capacity and lost efficiency. This work provides a suite of tools for instantiating ring-based lattice cryptography to work over subfields of cyclotomics, which provide more flexibility and better-fitting parameters for applications. A particular focus is on realizing FHE with optimal plaintext packing and homomorphic SIMD parallelism for any plaintext characteristic, along with efficient packed bootstrapping that fully exploits this parallelism. Toward this end, this (two-part) work makes the following main technical contributions, all of which are catalyzed by Galois theory: – For sampling and decoding errors in encryption and decryption (respectively), we construct geometrically short, structured bases for the number rings of arbitrary subfields of prime-power cyclotomics (and hence their composites as well). – For fast ring arithmetic, we define and establish analogous structural properties for Chinese Remainder Theorem (CRT) bases in abelian number rings, and give specialized fast transforms that map between CRT bases and any similarly structured bases. – For packed bootstrapping and homomorphic linear algebra, we give a general framework for homomorphic evaluation of structured linear transforms in abelian number rings, and show that CRT transforms can be evaluated using relatively few homomorphic operations. Image showing part 2 of abstract.
September 29, 2025 at 2:32 AM
chrispeikert.bsky.social
Thrilled to finally share this ⚡𝙣𝙚𝙬 𝙥𝙖𝙥𝙚𝙧⚡ with my (now-graduated!) student Zachary Pepin, which will appear at TCC 2025.

We tackle a frequent inconvenience in BGV/BFV-style homomorphic encryption: getting the desired kind of "SIMD slots" for plaintext packing. 🧵

web.eecs.umich.edu/~cpeikert/pu...
Screenshot of the title and abstract of the paper "Vive Galois! Part 1: Optimal SIMD Packing and Packed Bootstrapping for FHE", by Chris Peikert and Zachary Pepin. Abridged abstract: The vast majority of work on the efficiency of lattice-based cryptography, including fully homomorphic encryption (FHE), has relied on cyclotomic number fields and rings. This is because cyclotomics offer a wide variety of benefits, including good geometrical properties, fast ring arithmetic, and rich homomorphic operations like vectorized (SIMD) operations on "packed" plaintexts, automorphisms, and ring-switching. However, selecting a suitable cyclotomic that has the desired number and type of plaintext "slots," while also balancing security and efficiency, is a highly constrained problem that often lacks an ideal solution, resulting in wasted SIMD capacity and lost efficiency. This work provides a suite of tools for instantiating ring-based lattice cryptography to work over *subfields* of cyclotomics, which provide more flexibility and better-fitting parameters for applications. A particular focus is on realizing FHE with *optimal plaintext packing* and homomorphic SIMD parallelism for *any* plaintext characteristic, along with efficient packed bootstrapping that fully exploits this parallelism.
September 26, 2025 at 2:28 PM
Reposted by Chris Peikert
coachfinstock.bsky.social
What a gem of a movie. I ran into David Strathairn at Vetri in Philly while he was doing a play at the Wilma and when I shook his hand I said "Sneakers is one of my all time favorites" and he said "most fun I ever had and hardly anyone brings it up"

Gonna watch it tonight.
September 16, 2025 at 10:13 PM
chrispeikert.bsky.social
This is Ted Chiang erasure, Spelling Bee.
A Spelling Bee entry of the (pangram) word HEPTAPOD, which is the name of the aliens in Ted Chiang’s story “Story of Your Life”
September 14, 2025 at 12:26 PM
Reposted by Chris Peikert
nycsouthpaw.bsky.social
Acts of political violence aren’t acceptable. Non-political school shootings aren’t acceptable. Sacking the legislature isn’t acceptable. Military occupation of peaceful American cities isn’t acceptable. Abductions conducted in courthouse hallways by masked agents of the state aren’t acceptable.
September 10, 2025 at 8:36 PM
chrispeikert.bsky.social
This was, hands down, the top highlight among many in Pompeii.

Some ancient Roman had this beautiful floor mosaic made for his home entryway.

Is the red-eyed dog snarling and bearing its claws, barely held back by the links of a weak chain? Or is it wagging its tail and play-bowing? CAVEAT VIATOR!
chrispeikert.bsky.social Chris Peikert @chrispeikert.bsky.social · Aug 13
CAVE CANEM (beware of dog)
Mosaic in a house in Pompeii, with a picture of a dog and the text CAVE CANEM (beware of dog)
August 14, 2025 at 7:24 PM
Reposted by Chris Peikert
chrispeikert.bsky.social
CAVE CANEM (beware of dog)
Mosaic in a house in Pompeii, with a picture of a dog and the text CAVE CANEM (beware of dog)
August 13, 2025 at 8:24 PM