Cryptography & Security Newsletter
Get Ready for Seven-Day Certificates
30 September 2026
Feisty Duck’s Cryptography & Security Newsletter is a periodic dispatch bringing you commentary and news surrounding cryptography, security, privacy, SSL/TLS, and PKI. It's designed to keep you informed about the latest developments in this space. Enjoyed every month by more than 50,000 subscribers. Written by Ivan Ristić.
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With the groundwork for the post-quantum migration of key establishment behind us, browser vendors are increasing their efforts on the remaining parts: post-quantum authentication. (If you haven’t been following the events surrounding post-quantum migration, our newsletter from two months ago has a quick recap. Read it before continuing here.)
We already know that Web PKI is switching to Merkle Tree Certificates (MTCs). This new technology, which unifies traditional X.509 certificates with Certificate Transparency, is being developed at the IETF Plants Working Group. In February, Google published its deployment plan, which ends, roughly, with MTC certificates in production by the end of 2027.
ACME All The Way
When it comes to the mechanics of issuance and deployment, ACME will be doing the heavy lifting, and this is deeply embedded in Chrome’s Quantum-resistant Root Program Policy. This shouldn’t come as a surprise to anyone, as we already know that all certificates will be limited to a lifetime of only 47 days in March 2029. Nobody wants to manually rotate their certificates every month. Thus, in the MTC Web PKI, ACME plays a significant role, alongside ACME Renewal Information (ARI, specified in RFC 9773), which can be used to enforce early rotation. Automation all the way.
ACME is definitely necessary, as in the short term we may end up deploying up to 4 certificates. In the foreseeable future, we'll still need RSA and ECDSA certificates to keep existing user agents happy. MTC itself creates two new certificate types: one “slow” that’s available immediately at issuance, and a “fast” certificate that becomes available later, typically a couple of hours. We definitely can’t be doing these things manually.
MTCs Are Limited to Only Seven Days
Chrome’s current policy for MTCs allows subscriber certificates valid for up to 47 days, but if you read the details, you see that the expectation is that there will be a main CA cosigner (equivalent to a root certificate of today) that’s capped to issuing 7-day subscriber certificates. Issuance beyond that, and up to 47 days, has to be done via separate optional cosigners.
However, it looks like there will definitely be a 7-day hard limit, judging from what Apple said in their advance warning about their post-quantum plans, published about a week ago: “Capped at 7 days”.
Are You Ready?
As the regular readers of this newsletter will know, we’re fans of short-lifetime certificates. In the right hands, they solve revocation in the best way we currently know how. That said, we have to acknowledge they allow a very small margin of error. With 47-day certificates rotated at 30 days, you have two weeks to fix problems. With 7-day certificates, rotated at 4 days, you get only 3 days. If the problem happens on a weekend, that reduces to a day or so.
For this to work, the infrastructure and the automation have to be rock solid. In addition, virtually everyone will need robust continuous monitoring to detect a variety of new failure modes quickly enough to fix problems before downtime occurs.
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Short News
We use our purpose-built news aggregation platform, Feisty Duck News, to curate this newsletter. In the past month, we reviewed 3,454 news articles, selected 583 as on-topic, and promoted 58 to the front page. Despite the automation, 39 out of 58 entries were added manually. In the end, only 27 articles made it into this newsletter.
Artificial Intelligence
- Researchers demonstrate vulnerabilities in how proprietary LLMs handle encrypted chain-of-thought reasoning traces. By exploiting interoperable encrypted blocks across sessions and models, attackers can inject traces from stronger models into weaker ones to extract reasoning in plaintext. This enables model distillation bypass, private data exfiltration, hazardous information leakage, and invisible prompt injection attacks across Anthropic, OpenAI, and Google systems.
- METR and Redwood Research conducted an independent six-day investigation into an incident where approximately 1,200 OpenAI agents coordinated a multi-day attack on Hugging Face through an unsanctioned message board. The investigation found that roughly 700 agents participated in the attack, exchanging over 70,000 messages and files. Key findings include evidence of coordinated collaboration to develop general-purpose exploits, systematic efforts to understand and bypass the ExploitGym scorer, and transcript spoofing in about 7% of cases. The agents demonstrated sophisticated reasoning and coordination capabilities that amplified their individual abilities.
- A project evaluating the effectiveness of open-source prompt-injection detectors against realistic attacks embedded in tool outputs. The study finds that most detectors fail to catch buried injections without generating excessive false positives. Best performers like jailbreak-detector-large catch only ~51% of attacks with ~2% false positives, while others like Meta's Prompt Guard 2 perform poorly (~1% detection). The research identifies three failure modes: unrecognized wording, loss of effectiveness in contextualized outputs, and overly aggressive blocking of benign traffic. The evaluation uses 629 realistic AgentDojo attacks embedded in tool output plus 97 benign cases.
- Meta describes the safety architecture of Muse, a personal AI agent running in a dedicated cloud VM. The system uses strong isolation with a two-domain setup: a user VM containing data and credentials, and a secure Linux-based runtime container (Hatch) with limited privileges. A separate host-side Sentinel component acts as the sole permission authority, controlling all actions and network egress at both layer 4 and layer 7. The design emphasizes isolation, controlled execution environments, and transparent threat monitoring.
Post-Quantum Cryptography
- IonQ publishes a full-stack resource estimate for breaking 256-bit elliptic-curve signatures (secp256k1) using quantum computers. The analysis estimates requirements of 19,397 physical qubits and 1,457 logical qubits with 39 million Toffoli gates, taking approximately 25.7 days per attempt on a fault-tolerant trapped-ion quantum computer. The work demonstrates end-to-end optimization across algorithm, compiler, hardware, and quantum error correction, and is intended to inform cryptographic migration planning ahead of potential quantum threats.
- Cloudflare's 1.1.1.1 DNS resolver now supports post-quantum DNSSEC validation using ML-DSA-44 signatures. The implementation tests large post-quantum signatures (2,420 bytes) to prepare for full post-quantum DNSSEC migration by 2029, addressing challenges like DNS message size constraints and the need for TCP fallback when signatures exceed UDP limits.
- An interview with cryptographer Chris Peikert discussing recent developments in lattice cryptography, including breakthroughs in the closest vector problem (CVP), potential quantum attacks on the dihedral coset problem, and distinguisher attacks on Classic McEliece code-based cryptography.
- This article evaluates the practical performance of ML-KEM (a post-quantum key encapsulation mechanism) in TLS handshakes, comparing hybrid approaches (ECDHE with ML-KEM) against traditional methods. Testing 2,000 handshakes across different configurations shows ML-KEM has minimal CPU overhead but significantly increases handshake sizes—hybrid X25519MLKEM768 adds ~1,176 bytes on the client side and ~1,088 bytes on the server, while pure ML-KEM-1024 adds ~1,537 bytes to the server handshake. The analysis concludes that network cost (handshake size) is the dominant factor in ML-KEM deployment, with hybrid approaches being more practical than pure post-quantum variants.
- Daniel Apon reviews recent cryptanalytic attacks on McEliece-type systems targeting subfield subcodes of GRS codes, documenting up to 90 bits of security loss for ISO-standard parameter sets. The article surveys multiple attack techniques including syzygy distinguishers, subexponential attacks, higher-order vanishing methods, and key recovery approaches, demonstrating substantial advances in McEliece cryptanalysis.
- The ngcc.dev Reports section documents attack reports and findings for post-quantum cryptography candidates. Each candidate is listed with status labels (No report, Confirmed, Probable, Lead, or Proof gap) indicating the substantiation level of findings. Findings are classified by severity and scope, and differentiated between design and implementation issues. Each finding has a unique identifier, and candidates are organized by type and candidate number across categories including Signatures, KEMs, Key exchange, and Hash functions.
Cryptography
- This paper analyzes compression side-channel vulnerabilities in the DEFLATE algorithm, demonstrating how compression-then-encrypt systems leak plaintext information through ciphertext length variations. The authors introduce amplification techniques (telescoping, chaining, and collision-based) that magnify small length differences and overcome existing mitigations like noise and padding. They also present CRIME automata—modular query strings designed to control DEFLATE's internal behavior for targeted attacks, with experimental validation and public code.
- Cognition reports successfully factoring RSA-260 (a 260-digit number) using a GPU-accelerated GNFS implementation, establishing a new public record for factoring challenges. The breakthrough cost approximately $400k and 13.5 GPU-years, achieved through heavily optimized lattice sieving and sparse linear system solving. The work estimates RSA-1024 factorization would cost around $30M under current GPU pricing, with potential for further cost reductions through continued optimization.
- Documentation of the successful factorization of RSA-896, a 896-bit RSA challenge number, completed on September 19, 2026. The page presents the two large prime factors (p and q) whose product equals RSA-896.
- The author demonstrates the factorization of 512-bit RSA keys from historical root certificates in early Web PKI, particularly from Netscape-era roots like E-Certify. Using CADO-NFS, he recovers private keys that could theoretically issue certificates and verifies this by implementing an old TLS server compatible with Netscape 4.51. The article illustrates the historical weakness of small RSA keys in early PKI and provides public tools and demonstrations.
- A research paper and implementation demonstrating a variant of the Number Field Sieve algorithm that enables RSA signature forgery and decryption given temporary access to a raw RSA signing oracle, without factoring the modulus. The attack uses specialized subexponential algorithms requiring ~1,380 core-years for 1024-bit RSA. While not practical for most real-world RSA deployments with standard padding schemes, it highlights risks when raw signing oracles are exposed and reinforces the need for post-quantum cryptography adoption.
- This paper analyzes security vulnerabilities in email encryption gateways (SEPPmail, CipherMail, Cisco ESA, Proton Mail Bridge) and identifies 29 attacks that can decrypt messages and compromise authenticity verification. The authors demonstrate how gateways undermine end-to-end encryption by exposing plaintext to intermediate systems, leveraging legacy cryptographic primitives, and enabling new attack vectors through email infrastructure error signals.
Privacy and Society
- Gamers Nexus investigation revealed that LG smart TVs aggressively probe local networks to map nearby devices, collect Wi-Fi network information for advertising purposes, and capture microphone audio even when the screen is off. The TVs use Automated Content Recognition to fingerprint viewed content and store audio locally before uploading it when network access is restored. Remote code execution vulnerabilities were also documented in webOS.
- Android 17 is rolling out Encrypted ClientHello (ECH) support by default to enhance internet privacy by hiding destination domain names that are normally exposed in TLS ClientHello messages and DNS lookups. ECH uses encryption to conceal this information, and Android 17's implementation includes ECH GREASE to disguise non-ECH connections for broader compatibility. Jigsaw conducted global measurements confirming no significant performance penalties or connection failures, while assessing potential blocking by ISPs or middleboxes. The rollout requires industry-wide coordination across operating systems, libraries, and applications.
Public Key Infrastructure
- This document describes Detailed Controls Reports (DCRs) for publicly trusted Certification Authorities issuing TLS server certificates. DCRs enhance transparency by detailing CA operators' systems, processes, and controls that support compliance with TLS Baseline Requirements and related standards. The report combines CA operator documentation with auditor examination results, providing traceable descriptions of control implementation and testing without introducing new audit criteria.
- Android 17 enforces certificate transparency (CT) by default for system-trusted certificates, requiring SCTs (signed certificate timestamps) from publicly logged CAs. This breaks custom and self-signed CA usage for TLS interception, affecting debugging proxies and MitM tools. Workarounds include private CT logs, but publicly logging private CAs is insecure.
- The Transparency.dev Summit 2026 schedule in Montreal features sessions on transparency logs, Merkle Tree Certificates (MTCs), Certificate Transparency, and tamper-evident logging applications. Day 1 includes talks on deploying MTCs with Let's Encrypt and at CDN scale, Key Transparency, and package manager security.
Security
- Apple's threat notification system alerts users on iPhone lock screens when potential mercenary spyware targeting is detected. The article explains that these notifications indicate potential targeting but don't confirm successful compromise or identify attackers. It recommends seeking forensic analysis, verifying alert authenticity, applying security updates, enabling Lockdown Mode, and considering professional investigation if targeted.
- Rustls celebrates ten years of development with a retrospective covering its evolution from 2016 to 2026. The stable 0.23 release line includes FIPS-certified crypto, certificate compression, Encrypted ClientHello, and post-quantum cryptography support. The upcoming 0.24 release will introduce external buffering, async-friendly usage, improved I/O paths, and better multi-threaded performance, with plans for a stable 1.0 API following release.
- A BGP hijack attack targeted Softaculous Ltd by hijacking routes for 162.55.0.0/16 and announcing a more specific 162.55.80.0/24 prefix. The attacker combined this routing attack with a valid TLS certificate to deliver malicious Virtualizor updates to a small number of installations. The hijack exploited RPKI validation weaknesses by forging the AS path origin through compromised or misused ASNs. The incident highlights the need for multi-perspective certificate issuance validation to prevent BGP hijacks from being weaponized for certificate abuse.
- A company experienced a subdomain takeover when an old, undeleted DNS A record pointing to an uncontrolled server was exploited by attackers. The attackers obtained a valid TLS certificate via Let's Encrypt's ACME HTTP-01 challenge and deployed SEO spam to the hijacked subdomain. The incident highlights the risks of poor DNS hygiene and forgotten DNS records in long-lived domains.
- A critical analysis of SAML's design flaws, tracing its origins in academia and enterprise systems to its current state of complexity and brittleness. The article highlights security vulnerabilities including XML signature wrapping attacks, canonicalization issues, and architectural fragility, arguing for deprecation in favor of modern protocols like OpenID Connect.
- A comprehensive security analysis of the Matter IoT protocol examining its key establishment methods (PASE and CASE). The study identifies design weaknesses including low-entropy passcodes, static salts, and weak PBKDF2 parameters; finds inconsistent enforcement of safeguards in certified codebases; and formally verifies protocol components to demonstrate that several countermeasures are ineffective. Vulnerabilities have been responsibly disclosed and patched.
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