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Home News David Chaum’s New Quantum-Resistant Digital Currency, Praxxis, Has Arrived

David Chaum’s New Quantum-Resistant Digital Currency, Praxxis, Has Arrived

The Praxxis blockchain will feature a new approach to consensus-based on Chaum’s previous work in digital currencies, voting and distributed consensus spanning the past four decades


David Chaum, widely known for inventing the first digital currency, e-Cash, in the early 1980s, and Amsterdam-based DigiCash, an electronic cash company, in 1990s – has announced a new digital currency supported by a fresh, quantum-resistant blockchain called Praxxis. The xx collective, David Chaum’s community app, launched earlier this year, will allow users to test and interact with the Praxxis and Elixxir networks.

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Chaum added in a press release:

“I am thrilled to be able to reveal that we’re working on the Praxxis decentralized digital currency to support high-speed financial transactions. The world also needs Elixxir communication technology, since it is the only known practical way to shred the metadata that is inevitably created as we live our digital lives. A better type of consensus, compared to what powers current blockchains, is needed in order to support Elixxir—now running in Alpha without consensus. These are the reasons I’ve focused on the Praxxis project.”

Designed under Chaum’s leadership by a team working in stealth at Cayman Islands company, WBM Corp., the blockchain features a new approach to consensus-based on Chaum’s four decades of work on digital currency, voting, and distributed consensus. Praxxis currency has been designed to leverage the power of its sister Elixxir privacy-protecting platform.

The Praxxis consensus protocol simultaneously overcomes the scalability, privacy, and security challenges faced by legacy blockchains to deliver the “purely peer-to-peer version of electronic cash” that Satoshi called for in the first few words of his whitepaper.

Praxxis delivers blockchain performance capable of finalizing payments at the scale and speed required by a global transaction system and it uses a denominated coin structure that breaks payments into individual coins, which can then be commingled with coins associated with other payments to provide privacy.

And Praxxis uses distinctive cryptography which is fundamentally different from that promulgated by the government and which is strongly resistant even to quantum-level attack, thereby avoiding the rarely discussed yet fundamental security weaknesses of current widely-used cryptographic tools.

“The challenge is to make a digital currency that actually works for people,” WBM Corp. COO William Carter pointed out. “The technical requirements for speed and the requirements for privacy and security are usually in opposition. The Praxxis design breaks this tradeoff, which is an incredible achievement with really important, practical implications for performance.”

Using Elixxir, financial transactions denominated in Praxxis coins can be executed efficiently without leaking metadata. Alternatively, Praxxis can provide identified check-like wallet transactions.

The full technical details of the Praxxis approach will be included in a forthcoming whitepaper currently being prepared for release later this year.

In an exclusive Q and A interview with Blockchain News, Chaum gave more details on his perspective on the industry and his motivation.

Blockchain News:

“As a founding father of the digital cash and cryptography movement, it’s been some time since we have seen your work in the space. What has taken so long? With the controversies with the likes of Craig Wright and all kinds of weak propositions in this nascent space, your leadership and voice have been sorely missed.”

chaumsquareDavid Chaum:

“Without making comment on some of the early drama in the space, I do appreciate the sentiment implied in that question. The need for privacy-preserving technology and the potential of this “blockchain” technology (as it’s now called) has been the focus of my work since the late 70s and early 80s when I began working on technologies like mix networks, blind signatures, vault systems, e-cash, and more. Those technologies were designed to solve the very specific problem of digital privacy and data ownership.”

“Though I have enormous respect for what the crypto community has achieved in delivering store of value (with the success of bitcoin) and digital asset (with ethereal and STOs) technology, I’ve always been dedicated to protecting privacy as network adoption becomes predominant.”

“The thing about privacy-protecting technologies is the general public needs to care about the privacy problem in order to adopt the technology. A small, niche, a handful of us have cared for decades, but up until recently, that demand hasn’t existed en masse. It seems like we needed the “privacy Pearl Harbor” of the Snowden revelations and Cambridge Analytica to galvanize the masses demand for privacy.”

“The Snowden revelations were my personal wake-up call that privacy violations were happening at scale and I then knew that privacy was going to be back in the limelight again. It prompted me to revisit mix networks and vault systems to find better implementations. I focused on leveraging today’s stronger computing power and delivering a smartphone-based solution to meet the coming demand for real privacy in our online interactions. The breakthrough I had in designing a new mix of technology, where a framework and crypto could be precomputed, allowed us to address the efficiency/speed issue. Since then I have been working quietly with my teams to create a platform marrying modern-day versions of that privacy tech that can work at scale.”

“On the digital currency side, the digital bearer instrument technology I used at Digicash and the fixed denominated coin implementation (1 cent, 2 cent, 4 cent, 8 cent) structure is evident in our new Praxxis digital currency. But at Digicash the electronic cash had to be controlled and managed by banks as there was no decentralized, distributed network that could be entrusted with cash or anything of real value. The blockchain suggested a decentralized implementation and when we figured out how to design a consensus protocol that could perform quickly and scale, that’s when we made the decision to announce Praxxis.”

“So that’s what we’re up to, first with the Elixxir privacy-protecting platform and then with its sister Praxxis digital currency supported by the Praxxis blockchain and our new approach to consensus.”

Blockchain News:

“Do you feel you have solved what Vitalik Buterin and others call the Blockchain Trilemma? Security, scalability, and decentralization?”

David Chaum:

“Funny you should ask, Yes, we are building a platform that solves for the four requirements I believe to be absolutely vital for a blockchain platform to achieve mass adoption and provide real global utility – speed, privacy, security, and scalability.”

“In our consensus protocol we use a multi-party computation architecture so that a team of nodes divides up the work of reaching consensus, this fractional team can then reach finality for a block quickly without the full node population’s involvement in each block. We select each successive team for each block with a random selection algorithm and then the teams conduct a multi-party computation PRIOR to receiving specific data or message content, in this way they stand ready, as a team, to quickly process a specific block when they are called to. This precomputation is a breakthrough. Though the team size of 8 node runners can be constant, we can add more and more nodes to the entire population to select additional teams as we need capacity…as a result, we get a near-linear scaling in our system. The specification is100k+ quantum-secure transactions per second with finality in ~5 seconds, in complete privacy and metadata-resistance.”

Blockchain News:

“We have seen Dr. Silvio Micali from MIT backed with some $70 million in venture capital recently for his project called Algorand. Are there any plans to raise funds for the growth of Praxxis? Will this cryptocurrency eventually trade on cryptocurrency exchanges? Will there be a sale of some kind? What is the strategy, in a nutshell, for mass adoption?”

David Chaum:

“We will be revealing more information about these plans in the coming weeks. Right now our goal is to raise awareness that Praxxis exists, is almost finished, and help answer questions about how Praxxis and Elixxir will ultimately work together come MainNet launch. This system is effectively the culmination of 40 years work, so understandably it is a bit complex. We want to dedicate time and energy toward helping provide insight into the entire system, before introducing any additional new information.”

How Praxxis Works in A Nutshell

Praxxis technology is composed of three primary components: a blockchain, digital tokens, and a consensus mechanism, all designed to provide the first cash-like digital currency in the world and to support the operation of the Elixxir privacy-protecting platform.

In order for a digital currency to effectively support use cases for cash, it must be private, fast and secure. Most existing cryptocurrencies have had some level of success at achieving one of these characteristics but Praxxis is the first to accomplish all three.

Praxxis uses unique unlinkable transaction trees combined with denominated tokens to enable privacy-preserving payments when sent over the Elixxir messenger. With the personal check-like structure of other chains, it is inherently hard to keep specific transaction information private. For example, a $9.32 credit card transaction every other morning combined with metadata can tell an observer where your favourite breakfast spot is and what you generally order.

But Praxxis divides a single transaction into a number of identical-looking denominated tokens (like cash denominations) and with Elixxir stripping the metadata, it is impossible for an outside observer to gather data on your spending habits without your explicit permission.

The Praxxis consensus mechanism achieves transaction volumes and latencies capable of supporting a worldwide payments platform and resists centralization of power. This is done using a combination of innovations. A geographically binned worldwide network of nodes ensures efficient transactions and quick communication. And a fractional endorsement approach allows a transaction to reach finality without requiring all nodes in the network to sign off on it. An unmanipulatable randomness generator and transparent community governance allow for intelligent block team scheduling that doesn’t rely on inefficient Proof of Work algorithms or non-egalitarian Proof of Stake algorithms.

With any monetary instrument, security is paramount. Most existing digital infrastructure and blockchains are built on the security of elliptic curve public-key cryptography that is vulnerable to attack by quantum computing and possibly by nation-state adversaries (the NSA has already transitioned from elliptic curve cryptography to quantum-resistant cryptography). Praxxis is one of the first blockchain platforms to offer quantum-resistant signatures in both its consensus mechanism and token structure.

WBM Corp., led by William Carter, is one of the first companies domiciled in the Cayman Enterprise City in the Cayman Islands. Carter is a computer scientist with an extensive systems design background gained working in the blockchain space, in optics R&D, and earlier at JPL in Pasadena. The WBM team is made up of cryptographers, developers, operational personnel, and marketing professionals. Early work on the Praxxis chain was conducted at Privategrity Corporation in the Los Angeles area.

David Chaum is widely known for inventing the first digital currency, e-Cash, in the early 1980s, which he later deployed in the 1990s at his company DigiCash. He has also recently been credited with proposing the first decentralized blockchain as his Ph.D. dissertation at Berkeley in 1982. Chaum received the Information Technology European Award for 1995. In 2004, he was named an IACR Fellow. In 2010, he received during the RSA Conference the RSA Award for Excellence in Mathematics. Chaum is credited as the inventor of secure digital cash for his 1982 paper, which also introduced the cryptographic primitive of a blind signature. These ideas have been described as the technical roots of the vision of the Cypherpunk movement that began in the late 1980s. Chaum’s proposal allowed users to obtain digital currency from a bank and spend it in a manner that is untraceable by the bank or any other party. In 1988, he extended this idea (with Amos Fiat and Moni Naor) to allow offline transactions that enable detection of double-spending.

More words from Chaum on a Bloomberg podcast.

Bloomberg Podcast: David Chaum – Meet The Godfather Of Crypto, Who’s Been Working On Digital Currency Since The Early 80s – By Tracy Alloway and Joe Weisenthal

David Chaum live on stage describing Elixxir

An app and David Chaum’s community, the xx collective, is available on iOS and Android to support participation for Praxxis on the way to MainNet and for Elixxir as a privacy-protecting platform. Information is also available at The team will share more information and the full technical details of the Praxxis approach in the forthcoming whitepaper currently being prepared for release later this year. And specific issues will likely be discussed on Discord prior to that.

Here’s a bit of fun, this is pulled from a 1981 book called Applied Cryptography by Bruce Schneier. 

You can’t go out to dinner with a bunch of cryptographers without raising a ruckus. David Chaum introduces the Dining Cryptographers Problem.

“Three cryptographers are sitting down to dinner at their favourite three-star restaurant. Their waiter informs them that arrangements have been made with the maître d‘hôtel for the bill to be paid anonymously. One of the cryptographers might be paying for the dinner, or it might have been the NSA. The three cryptographers respect each other’s right to make an anonymous payment, but they wonder if the NSA is paying. How do the cryptographers, named Alice, Bob, and Carol, determine if one of them is paying for dinner, while at the same time preserving the anonymity of the payer?”

Click here to see the solution on page 125.


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