For several years, CryptoHack has been a free platform for learning modern cryptography through fun and challenging programming puzzles. From toy ciphers to post-quantum cryptography, CryptoHack has a wide-ranging and ever increasing library of puzzles for both the aspiring and accomplished cryptographer. On this episode, Nadim and Lucas are joined by Giacomo Pope and Laurence Tennant, the founders of CryptoHack, to discuss how the platform came to be, and how it evolved, as well as how to improve cryptographic pedagogy more broadly. Special Guests: Giacomo Pope and Laurence Tennant.

On April 19th 2022, Neil Madden disclosed a vulnerability in many popular Java runtimes and development kits. The vulnerability, dubbed "Psychic Signatures", lies in the cryptography for ECDSA signatures and allows an attacker to bypass signature checks entirely for these signatures. How are popular cryptographic protocol implementations in Java affected? What's the state of Java cryptography as a whole? Join Neil, Nadim and Lucas as they discuss. Music composed by Yasunori Mitsuda. Special Guest: Neil Madden.

Threema is a Swiss encrypted messaging application. It has more than 10 million users and more than 7000 on-premise customers. Prominent users of Threema include the Swiss Government and the Swiss Army, as well as the current Chancellor of Germany, Olaf Scholz. Threema has been widely advertised as a secure alternative to other messengers. Kenny, Kien and Matteo from the ETH Zurich Applied Cryptography Group present seven attacks against the cryptographic protocols used by Threema, in three distinct threat models. All the attacks are accompanied by proof-of-concept implementations that demonstrate their feasibility in practice. Links and papers discussed in the show: * Three Lessons from Threema (https://breakingthe3ma.app/) Special Guests: Kenny Paterson, Kien Tuong Truong, and Matteo Scarlata.

Benjamin Wesolowski talks about his latest paper in which he mathematically proved that the two fundamental problems underlying isogeny-based cryptography are equivalent. Links and papers discussed in the show: * The supersingular isogeny path and endomorphism ring problems are equivalent (https://eprint.iacr.org/2021/919) * Episode 5: Isogeny-based Cryptography for Dummies! (https://www.cryptography.fm/5) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guest: Benjamin Wesolowski.

A team of cryptanalysits presents the first publicly available cryptanalytic attacks on the GEA-1 and GEA-2 algorithms. Instead of providing full 64-bit security, they show that the initial state of GEA-1 can be recovered from as little as 65 bits of known keystream (with at least 24 bits coming from one frame) in time 240 GEA-1 evaluations and using 44.5 GiB of memory. The attack on GEA-1 is based on an exceptional interaction of the deployed LFSRs and the key initialization, which is highly unlikely to occur by chance. This unusual pattern indicates that the weakness is intentionally hidden to limit the security level to 40 bit by design. Cryptanalysis of the GPRS Encryption Algorithms GEA-1 and GEA-2 (https://eprint.iacr.org/2021/819) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guests: Gaëtan Leurent and Håvard Raddum.

TLS is an internet standard to secure the communication between servers and clients on the internet, for example that of web servers, FTP servers, and Email servers. This is possible because TLS was designed to be application layer independent, which allows its use in many diverse communication protocols. ALPACA is an application layer protocol content confusion attack, exploiting TLS servers implementing different protocols but using compatible certificates, such as multi-domain or wildcard certificates. Attackers can redirect traffic from one subdomain to another, resulting in a valid TLS session. This breaks the authentication of TLS and cross-protocol attacks may be possible where the behavior of one protocol service may compromise the other at the application layer. Links and papers discussed in the show: * ALPACA Attack Website (https://alpaca-attack.com/) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guests: Marcus Brinkmann and Robert Merget.

Nadim talks with Peter Schwabe and Matthias Kannwischer about the considerations — both in terms of security and performance — when implementing cryptographic primitives for low-level and embedded platforms. Links and papers discussed in the show: * Optimizing crypto on embedded microcontrollers (https://cryptojedi.org/peter/data/coins-20170830.pdf) * Implementing post-quantum cryptography on embedded microcontrollers (https://cryptojedi.org/peter/data/graz-20190917.pdf) * Optimizing crypto on embedded microcontrollers (ASEC 2018) (https://cryptojedi.org/peter/data/asec-20181210.pdf) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guests: Matthias Kannwischer and Peter Schwabe.

Wi-Fi is a pretty central technology to our daily lives, whether at home or at the office. Given that so much sensitive data is regularly exchanged between Wi-Fi devices, a number of standards have been developed to ensure the privacy and authentication of Wi-Fi communications. However, a recent paper shows that every single Wi-Fi network protection standard since 1997, from WEP all the way to WPA3, is exposed to a critical vulnerability that allows the exfiltration of sensitive data. How far does this new attack go? How does it work? And why wasn’t it discovered before? We’ll discuss this and more in this episode of Cryptography FM. Links and papers discussed in the show: * Fragment and Forge: Breaking Wi-Fi Through Frame Aggregation and Fragmentation (https://papers.mathyvanhoef.com/usenix2021.pdf) * Dragonblood: Analyzing the Dragonfly Handshake of WPA3 and EAP-pwd (https://papers.mathyvanhoef.com/dragonblood.pdf) * Release the Kraken: New KRACKs in the 802.11 Standard (https://papers.mathyvanhoef.com/ccs2018.pdf) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guest: Mathy Vanhoef.

Contact discovery is a core feature in popular mobile messaging apps such as WhatsApp, Signal and Telegram that lets users grant access to their address book in order to discover which of their contacts are on that messaging service. While contact discovery is critical for WhatsApp, Signal and Telegram to function properly, privacy concerns arise with the current methods and implementations of this feature, potentially resulting in the exposure of a range of sensitive information about users and their social circle. Do we really need to rely on sharing every phone number on our phone in order for mobile messengers to be usable? What are the privacy risks, and do better cryptographic alternatives exist for managing that data? Joining us are researchers looking exactly into this problem, who will tell us more about their interesting results. Links and papers discussed in the show: All the Numbers are US: Large-scale Abuse of Contact Discovery in Mobile Messengers (https://www.ndss-symposium.org/wp-content/uploads/ndss2021_1C-3_23159_paper.pdf) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guests: Alexandra Dmitrienko, Christian Weinert, and Christoph Hagen.

Secure multi-party computation is a fascinating field in cryptography, researching how to allow multiple parties to compute secure operations over inputs while keeping those inputs private. This makes multi-party computation a super relevant technology in areas such as code signing, hospital records and more. But what does it take to bring secure multi-party computation from the blank slate of academia and into the messiness of the real world? Today on Cryptography FM, we’re joined by Dr. Yehuda Lindell and Dr. Nigel Smart, from Unbound Security, to tell us about their research, their experiences with real world secure multiparty computation, and more. Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guests: Nigel Smart and Yehuda Lindell.

On March 1st, 2021, a curious paper appeared on the Cryptology ePrint Archive: senior cryptographer Claus Peter Schnorr submitted research that claims to use lattice mathematics to improve the fast factoring of integers so much that he was able to completely “destroy the RSA cryptosystem” -- certainly a serious claim. Strangely, while the paper’s ePrint abstract did mention RSA, the paper itself didn’t. Two days later, Schnorr pushed an updated version of the paper, clarifying his method. Does Schnorr’s proposed method for “destroying RSA” hold water, however? Some cryptographers aren’t convinced. Joining us today is Leo Ducas , a tenured researcher at CWI, Amsterdam who specialises in lattice-based cryptography, to help us understand where Schnorr was coming from, whether his results stand on their own, and how the influence of lattice mathematics in applied cryptography has grown over the past decade. Links and papers discussed in the show: * Schnorr's ePrint submission (https://eprint.iacr.org/2021/232) * Leo Ducas's implementation of Schnorr's proposed algorithm in Sage (https://github.com/lducas/SchnorrGate) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guest: Léo Ducas.

Zero-Knowledge proofs have broadened the realm of use cases for applied cryptography over the past decade, from privacy-enhanced cryptocurrencies to applications in voting, finance, protecting medical data and more. In 2018, Dr. Eli Ben-Sasson and his team introduced ZK-STARKs, a new zero-knowledge construction that functions without trusted setup, thereby broadening what zero-knowledge systems are capable of. We’ll talk about ZK-STARKs and more with Eli in this episode of Cryptography FM. Links and papers discussed in the show: * Scalable, transparent, and post-quantum secure computational integrity (https://eprint.iacr.org/2018/046.pdf) * Cairo Language (https://www.cairo-lang.org) * Cairo Workshop, 14-15 March 2021! (https://www.eventbrite.com/e/cairo-101-workshop-i-tickets-142918738795) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guest: Eli Ben-Sasson.

Every year, the IACR Real World Cryptography symposium brings together researchers, engineers and practitioners in applied cryptography to discuss cryptography that matters, in the real world. To me, this is the big one! The one cryptography conference that matters the most. Who needs proceedings when you’ve got so much excitement in the air, and so many results and projects that actually have a measurable impact on how cryptography affects the real world? This year’s program is maybe the most exciting yet, with talks on secure channel protocols, multiparty computation, formal methods, post-quantum cryptography, humans, policy and cryptography, hardware, cryptocurrency, cryptography for the cloud, anonymity and more. So many exciting talks! So much new research to discuss! Like every year, Real World Crypto is shaping up to be a veritable who’s who of applied cryptography. In this special episode of Cryptography FM, I’m joined by fellow researcher Benjamin Lipp in order to just… candidly go through the program of Real World Crypto 2021 and covering each talk’s abstract briefly. We’re going to have another special episode after Real World Crypto 2021 as a post-conference episode in order to discuss the highlights of the conference. And hopefully we’ll do this every year here on Cryptography FM! Music composed by Toby Fox and performed by The Consouls (https://www.youtube.com/watch?v=5jUwV8_h7ZY). Special Guest: Benjamin Lipp.

The race for post-quantum cryptographic signature primitives is in its final lap over at NIST, which recently announced DILITHIUM, FALCON and Rainbow as the three signature primitive finalists. But a paper recently published by KU Leuven researcher Ward Beullens claims to find serious weaknesses in the security of Rainbow, one of those three finalists. In fact, the paper claims that the weaknesses are so severe that Rainbow’s security parameters now fall short of the security requirements set out by the NIST post-quantum competition. But how does Rainbow work, and how do these weaknesses affect it? And why weren’t they spotted until now? We discuss this and more in this week’s episode of Cryptography FM. Links and papers discussed in the show: * Improved Cryptanalysis of UOV and Rainbow (https://eprint.iacr.org/2020/1343) * SQISign: compact post-quantum signatures from quaternions and isogenies (https://eprint.iacr.org/2020/1240) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guest: Ward Beullens.

Authenticated encryption such as AES-GCM or ChaCha20-Poly1305 is used in a wide variety of applications, including potentially in settings for which it was not originally designed. A question given relatively little attention is whether an authenticated encryption scheme guarantees “key commitment”: the notion that ciphertext should decrypt to a valid plaintext only under the key that was used to generate the ciphertext. In reality, however, protocols and applications do rely on key commitment. A new paper by engineers at Google, the University of Haifa and Amazon demonstrates three recent applications where missing key commitment is exploitable in practice. They construct AES-GCM ciphertext which can be decrypted to two plaintexts valid under a wide variety of file formats, such as PDF, Windows executables, and DICOM; and the results may shock you. Links and papers discussed in the show: * How to Abuse and Fix Authenticated Encryption Without Key Commitment (https://eprint.iacr.org/2020/1456) * Mitra, Ange's software tool for generating binary polyglots (https://github.com/corkami/mitra) * Shattered and other research into hash collisions (https://github.com/corkami/collisions) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guests: Ange Albertini and Stefan Kölbl.

Before there was Signal, before there was WhatsApp, the realm of secure encrypted messaging was ruled by the Off-the-Record secure messaging protocol, created as an alternative to PGP that introduced security properties like forward secrecy and deniability that were considered exotic at the time. Now, more than a decade later, Off-the-Record messaging, or OTR, has been largely sidelined by Signal variants. But a small team of cryptography engineers is still working on pushing Off-the-Record messaging forward by focusing on use cases that they argue aren’t sufficiently covered by Signal. But what even is deniability, and how much does it matter in the real-world context of secure messaging? Sofía Celi joins us in today’s episode to talk about this and more. Links and papers discussed in the show: * OTRv4 (https://github.com/otrv4/otrv4) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guest: Sofía Celi.

Elliptic-curve signatures have become a highly used cryptographic primitive in secure messaging, TLS as well as in cryptocurrencies due to their high speed benefits over more traditional signature schemes. However, virtually all signature schemes are known to be susceptible to misuse, especially when information about the nonce is leaked to an attacker. LadderLeak is a new attack that exploits side channels present in ECDSA, claiming to allow real-world breaking of ECDSA with less than a bit of nonce leakage. But what does “less than a bit” mean in this context? Is LadderLeak really that effective at breaking ECDSA, with so little information to go on? Joining us this episode are LadderLeak co-authors Akira Takahashi, Mehdi Tibouchi and Yuval Yarom to discuss these questions and more. Links and papers discussed in the show: * LadderLeak: Breaking ECDSA With Less Than One Bit Of Nonce Leakage (https://eprint.iacr.org/2020/615) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guests: Akira Takahashi, Mehdi Tibouchi, and Yuval Yarom.

Secure messaging protocols like Signal have succeeded at making end-to-end encryption the norm in messaging more generally. Whether you’re using WhatsApp, Wire, Facebook Messenger’s Secret Chat feature, or Signal itself, you’re benefiting from end-to-end encryption across all of your messages and calls, and it’s so transparent that most users aren’t even aware of it! One area in which current secure messaging protocols have stalled, however, is the ability to scale secure conversations to groups of dozens, hundreds and even thousands of people. But the IETF’s Messaging Layer Security, or MLS, effort aims to make that happen. Bringing together a collaboration between Wire, Mozilla, Cisco, Facebook, as well as academia, MLS wants to become the TLS of secure messaging, and make it possible to hold secure conversations scaling to thousands of participants. But what are the real-world implementation risks involved? Are conversations even worth securing when you’ve got hundreds of potential leakers? Links and papers discussed in the show: * MLS Website (https://messaginglayersecurity.rocks/) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guest: Raphael Robert.

Zero-knowledge proofs have been a notorious research target ever since Zcash and other cryptocurrencies have invented lots of new use cases for them. Range proofs, bullet proofs, you name it – all kinds of zero-knowledge mechanisms have received more and more attention. But what about using zero-knowledge proofs to prove the existence of a software vulnerability? That way, you can prove that you have a zero-day without risking it getting stolen, putting both vulnerability researchers as well as companies looking to secure their software in a better position! That’s what Dr. David Archer from Galois is working on, and he joins me today on Cryptography FM to discuss this new interesting use case, and more. Links and papers discussed in the show: * Galois Fromager (https://galois.com/project/fromager/) * Using GANs for Sharing Networked Time Series Data: Challenges, Initial Promise, and Open Questions (https://arxiv.org/abs/1909.13403) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guest: David Archer.

The NIST post-quantum competition has started a race for post-quantum cryptography. As a result, we’ve seen a great deal of research into alternative hard mathematical problems to use as a basis for public-key cryptography schemes. Lattice-based cryptography! Error-correcting code based cryptography! And of course, isogeny-based cryptography, have all received enormous renewed interest as a result. While the NIST post-quantum competition recently announced that it’s favoring candidates founded on lattice-based cryptography, it also encouraged further research into isogeny-based cryptography. But what even is isogeny-based cryptography? Is it as intimidating as it sounds? And what’s keeping it behind on NIST’s list of post-quantum primitives? Today, it’s my pleasure to be joined by isogeny-based cryptography researchers Luca de Feo and Hart Montgomery, co-authors of a recent publication titled “Cryptographic Group Actions and Applications”, which Luca affectionately described as a “isogeny-based cryptography for dummies” paper. We’ll be discussing isogeny-based cryptography and more. Links and papers discussed in the show: * Cryptographic Group Actions and Applications (https://eprint.iacr.org/2020/1188) * CSIDH Intro (https://csidh.isogeny.org/) Music composed by Toby Fox and performed by Sean Schafianski (https://seanschafianski.bandcamp.com/). Special Guests: Hart Montgomery and Luca De Feo.