"Signature forgery." It's a new way to break RSA keys — and it doesn't require factoring. Ars Technica reports on new research using classical computing to "reduce the current RSA security level to an unacceptably low threshold" and lower the required computing resources by orders of magnitude. There's "a gap in current RSA-type security assumptions," according to a paper co-authored by University of California, San Diego professor Nadia Heninger, who argues that gap "gives classical cryptanalytic evidence in favor of moving away from RSA entirely during the current post-quantum transition." The practical risk is limited, but still significant. Applying the attack against the deprecated use of 1024-bit keys took a handful of months on an academic CPU cluster, significantly less than the current estimates for 1024-bit factoring that would require resources that only nations or companies with massive resources could achieve. Widely used RSA implementations are also safe. Nonetheless, the research has taken cryptographers by surprise... "If this result holds up under peer review, it would indeed be a conceptual break-through," Karsten Nohl, a cryptography expert and the head of innovation at Allurity, said in an interview. "RSA is as difficult to break as it is to factor large integers, at least so we thought. The researcher suggests that you can practically break RSA without cracking its key...." The key forgery attack Heninger and the other researchers devised poses an immediate threat to 1024-bit RSA. Even for 2048- and 4096-bit keys, the method reduces the security of RSA to unacceptable levels. The National Security Agency, National Institute of Standards and Technology, and European Union Agency for Network and Information Security require that any cryptosystem should provide a level of no less than 128 or more bits, meaning the operations required must exceed 2**128. The forgery attack drops these levels to 2**65, 2**90, and 2**119 for 1024-, 2048-, and 4096-bit keys respectively. These levels may further drop because Heninger's team did all the coding by hand and used no AI or GPUs in performing the forgeries. The researcher said these tools will "almost certainly" drop the security levels further. The attack works only against blind-signature implementations of RSA... Still, some real-world systems continue to use blind-signature, also known as textbook, RSA... The paper's authors and other researchers stress that the new attack poses little real-world threat. It does, however, drastically lower the estimated security of textbook RSA, and it does so in a way no one knew of previously... The new attack will further increase the urgency of completely moving away from the cryptosystem. Thanks to long-time Slashdot reader phatrabt for sharing the article.

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Long-time Slashdot reader BrianFagioli is announcing that he's released a new iPhone app that creates a cryptographic witness for photos without uploading the original image. The app hashes the file, signs the hash using a dedicated identity stored in Apple Keychain, and publishes the witness to Nostr relays while keeping the photo inside the app unless the user chooses to export it. Rather than trying to determine whether a scene was genuine, the app — named Veridenz — answers a narrower question, by verifying whether a photo file matches the one that was originally witnessed. Users do not need a Nostr account because the app creates its own signing identity, keeping private documentation separate from a public Nostr profile. "The developer does not collect any data from this app," says its page in Apple's iPhone store. The app's tagline is "Capture. Prove. Verify."

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Long-time Slashdot reader BrianFagioli is announcing that he's released a new iPhone app that creates a cryptographic witness for photos without uploading the original image. The app hashes the file, signs the hash using a dedicated identity stored in Apple Keychain, and publishes the witness to Nostr relays while keeping the photo inside the app unless the user chooses to export it. Rather than trying to determine whether a scene was genuine, the app — named Veridenz — answers a narrower question, by verifying whether a photo file matches the one that was originally witnessed. Users do not need a Nostr account because the app creates its own signing identity, keeping private documentation separate from a public Nostr profile. "The developer does not collect any data from this app," says its page in Apple's iPhone store. The free app's tagline is "Capture. Prove. Verify."

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An anonymous reader quotes a report from The Guardian: Apple has launched a new legal challenge against a UK government demand to access its customers' highly encrypted data, a year after the Home Office agreed to abandon its previous request. The US tech company launched the legal complaint last month at the Investigatory Powers Tribunal (IPT), an independent court that has the power to investigate claims that the UK intelligence services have acted unlawfully. The UK government had made a second request to Apple to grant it a "back door" to encrypted iCloud data belonging to British users, according to an order issued by the court. Britain backed down on its original demand for access to data from UK and US customers last year, after a heated transatlantic tussle over encryption between London and Washington. UK authorities subsequently issued a new "technical capability notice" (TCN) to Apple that did not apply to American users. Apple is seeking to challenge the British government's powers to issue TCNs under the UK Investigatory Powers Act, according to the details of the new legal case first reported by the Financial Times. [...] The original TCN issued last year asked Apple for the right to see users' encrypted data protected by its advanced data protection (ADP) program in the event of a national security risk. Apple said the removal of the tool -- which not even it can access -- would make users more vulnerable to data breaches from bad actors and other threats to customer privacy. Creating a "back door" would also mean all data was accessible by Apple, which it could be forced to share with law enforcement possessing a warrant. As a result, Apple withdrew UK customers' access to its ADP program in January 2025. The Home Office has maintained that the Investigatory Powers Act, under which such orders are issued, contains robust safeguards and is used only when absolutely necessary.

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