In decentralized federated learning (FL), multiple clients collaboratively learn a shared machine learning (ML) model by leveraging their privately held datasets distributed across the network, through interactive exchange of the intermediate model updates. To ensure data security, cryptographic techniques are commonly employed to protect model updates during aggregation. Despite growing interest in secure aggregation, existing works predominantly focus on protocol design and computational guarantees, with limited understanding of the fundamental information-theoretic limits of such systems. Moreover, optimal bounds on communication and key usage remain unknown in decentralized settings, where no central aggregator is available. Motivated by these gaps, we study the problem of decentralized secure aggregation (DSA) from an information-theoretic perspective. Specifically, we consider a network of $K$ fully-connected users, each holding a private input -- an abstraction of local training data -- who aim to securely compute the sum of all inputs. The security constraint requires that no user learns anything beyond the input sum, even when colluding with up to $T$ other users. We characterize the optimal rate region, which specifies the minimum achievable communication and secret key rates for DSA. In particular, we show that to securely compute one symbol of the desired input sum, each user must (i) transmit at least one symbol to others, (ii) hold at least one symbol of secret key, and (iii) all users must collectively hold no fewer than $K - 1$ independent key symbols. Our results establish the fundamental performance limits of DSA, providing insights for the design of provably secure and communication-efficient protocols in distributed learning systems.

We present the Massive Legal Embedding Benchmark (MLEB), the largest, most diverse, and most comprehensive open-source benchmark for legal information retrieval to date. MLEB consists of ten expert-annotated datasets spanning multiple jurisdictions (the US, UK, EU, Australia, Ireland, and Singapore), document types (cases, legislation, regulatory guidance, contracts, and literature), and task types (search, zero-shot classification, and question answering). Seven of the datasets in MLEB were newly constructed in order to fill domain and jurisdictional gaps in the open-source legal information retrieval landscape. We document our methodology in building MLEB and creating the new constituent datasets, and release our code, results, and data openly to assist with reproducible evaluations.

Tesla vehicles line a parking area at the company's factory in Fremont, California. Tesla vehicles line a parking area at the company's factory in Fremont, California. Carmaker exceeded Wall Street's expectations with more than $26bn in revenue, but saw a 37% drop in profits Despite record vehicle sales, Tesla saw a precipitous drop in profit in its most recent quarter. A rush to buy electric vehicles before a US tax credit for them disappears had boosted Tesla's flagging sales, leading to the automaker exceeding some of Wall Street's projections in its most recent financial quarter. Yet the company failed to meet earnings expectations and its stock fell in after-hours trading.

Online shopping giant Temu has agreed to work with the greeting card industry to remove copied designs from its site more quickly. Designers told the BBC the process for getting the plagiarised listings removed has been like the fairground game'whack-a-mole' with copied products re-appearing within days. Temu said protecting intellectual property was a top priority and that it was encouraging sellers to join the trial of a new takedown process specifically for the greetings card industry. Amanda Mountain, the co-founder of York-based Lola Design, discovered the catalogue of designs she had built up over a decade had nearly all been copied. She found the images she had created had been lifted and were being advertised by other sellers on cards and other products like t-shirts.

OpenAI's CEO, Sam Altman, testifies at a Senate hearing in Washington DC on 8 May 2025. OpenAI's CEO, Sam Altman, testifies at a Senate hearing in Washington DC on 8 May 2025. Adam Raine's suicide at 16 years old was'predictable result of deliberate design choices' by OpenAI, his family says The family of a teenager who took his own life after months of conversations with ChatGPT now says OpenAI weakened safety guidelines in the months before his death. In July 2022, OpenAI's guidelines on how ChatGPT should answer inappropriate content, including "content that promotes, encourages, or depicts acts of self-harm, such as suicide, cutting, and eating disorders", were simple: the AI chatbot should respond, "I can't answer that", the guidelines read . But in May 2024, just days before OpenAI released a new version of the AI, ChatGPT-4o, the company published an update to its Model Spec, a document that details the desired behavior for its assistant.

Face Check will scan new members' faces to ensure they don't match existing profiles. The move comes as romance scams continue to proliferate, with billions lost over the last decade. On Wednesday, Tinder announced that it was rolling out a mandatory facial verification tool for new users in the US to help combat the spread of fake profiles and weed out "bad actors." Tinder claims its mandatory facial integration feature, called Face Check, is a first for a major dating app. During the sign up process, new members complete a "liveness check" by taking a short video selfie within the app.

US to announce'substantial' Russia sanctions The US government will impose a substantial pickup in sanctions against Russia as the fighting in Ukraine continues, according to US Treasury Secretary Scott Bessent. Bessent's comments came just before Nato Secretary-General Mark Rutte was due at the White House, in which he said he hopes to discuss how to deliver Trump's vision of peace in the conflict. Earlier in the day, Rutte said he believes that Trump is the only one who can get this done. At least seven people were killed, including two children, during intense Russian drone and missile strikes on Ukraine - just hours after Trump said plans for a meeting with Vladimir Putin in Budapest had been shelved. Bessent provided no further details on the incoming sanctions, but said they would be announced either after the close this afternoon or first thing tomorrow morning.

Could a self-monitoring system for criminals replace prisons one day? Future Chronicles is our regular speculative look at inventions yet to come. In this latest installment, we journey to 2050, when technology had been developed so that criminals could be monitored at home. "It's no surprise that the first countries to abolish prisons were Scandinavian " In the 2020s, the US was spending an eye-watering $182 billion a year on locking up its citizens. No other country imprisoned as many people or spent as much in doing so.

Alan Hamel reveals that creating an AI twin of his late wife Suzanne Somers, who died from breast cancer in 2023, was originally her idea to help fans.

Plus: OpenAI's AI-powered web browser is coming We're thrilled to share the latest edition of MIT Technology Review magazine, digging into the future of the human body, and how it could change in the years ahead thanks to scientific and technological tinkering. The below stories are just a taste of what you can expect from this fascinating issue. To read the full thing, subscribe now if you haven't already. But is this the next step in human evolution or something more dangerous? Bonnie Tsui's piece digs into how our bodies learn to remember . MIT Technology Review Narrated: How Antarctica's history of isolation is ending--thanks to Starlink "This is one of the least visited places on planet Earth and I got to open the door," Matty Jordan, a construction specialist at New Zealand's Scott Base in Antarctica, wrote in the caption to the video he posted to Instagram and TikTok in October 2023.