In the early bitcoin years, proponents promised that you would soon be able to pay for anything and everything with cryptocurrency. Order pizza! Buy Etsy trinkets! Use a bitcoin ATM! While PayPal had existed for more than a decade, frictionless, social payment platforms like Venmo were just first taking off, and cryptocurrency seemed like a legitimate way for digital transactions to evolve.

It didn't happen. Cryptocurrency remains confusing and challenging for the average person to acquire and manage, much less sell. And the protocols that underlie bitcoin and other mainstream cryptocurrencies like ethereum suffer significant scalability and transaction bottleneck issues. Visa currently processes about 3,674 transactions per second; the best bitcoin network might be able to process seven per second.

But now the creator of the dead simple end-to-end encrypted messaging app Signal, Moxie Marlinspike, is on a mission to overcome those limitations, and to create a streamlined digital currency that's private, easy-to-use, and allows for quick transactions from any device. And while it may feel like the last thing the world needs is yet another cryptocurrency, Marlinspike's track record with Signal—and the organization behind it, Open Whisper Systems—makes this a project worth watching.

Coin Toss

The currency Marlinspike has been working on as technical advisor for the last four months, alongside technologist Joshua Goldbard, is MobileCoin. The two based it on the open-source Stellar Consensus Protocols platform, an alternative payment network that underlies systems like an inter-bank payment network run by IBM in the South Pacific, and the low-fee international money transfer service Tempo in Europe.

'Usability is the biggest challenge with cryptocurrency today.' Signal Creator Moxie Marlinspike

The Stellar blockchain is also generally regarded as being faster and more efficient than its predecessors; On Wednesday, the mobile messaging service Kik announced that it will move its Kin cryptocurrency platform from Ethereum to Stellar. "We've been using Ethereum to date, and to be honest I call it the dial-up era of blockchain," CEO Ted Livingston said.

MobileCoin wants to leverage an extensive architecture to add simplicity to real privacy protections and resilience against attacks. The ultimate goal: To make MobileCoin as intuitive as any other payment system.

That vision mirrors the animating purpose of Signal, which was developed to make robust end-to-end encrypted communication as easy and straightforward as less secure options, a simple experience that belies the complex cryptographic communication protocols that enable it.

"I think usability is the biggest challenge with cryptocurrency today," says Marlinspike. "The innovations I want to see are ones that make cryptocurrency deployable in normal environments, without sacrificing the properties that distinguish cryptocurrency from existing payment mechanisms."

Usability efforts for older generation cryptocurrency protocols, like bitcoin, have largely been left to services like Coinbase, which centralize everything from currency exchange to your wallet, key management, and processing transactions. These platforms make actually using cryptocurrency more realistic for the average person, but they also consolidate mechanisms that are meant to be kept separate in the private and decentralized concept of cryptocurrency. They generally detail extensive privacy and security protections, but they do require users to trust both their intentions and implementation.

By contrast, the idea of MobileCoin is to build a system that hides everything from everyone, leaving fewer (or theoretically no) opportunities for abuse.

On the Node

Ideally, there would be a way to fix the structural problems of existing cryptocurrencies, rather than creating another new offering. But Marlinspike and Goldbard concluded that the only way to orient a cryptocurrency around user needs was to start from scratch, and architect everything with that "target user experience" in mind.

To that end, MobileCoin delegates all the complicated and processing-intensive work of participating in a blockchain ledger and validating transactions to nodes—servers with constant connectivity that store and work on a fully updated copy of a currency's blockchain. The nodes can then provide software services to users, like apps that seamlessly integrate easy and quick MobileCoin transactions. The nodes also handle key management for users, so the public—and particularly the private—numeric sequences that encrypt each person's transactions are stored and used by the node. But crucially MobileCoin is designed so the node operators can never directly access users' private keys.

'If you can’t look at the ledger, how can you cheat it?' Joshua Goldbard, MobileCoin

This is where the special features of MobileCoin come in. The currency is designed to utilize an Intel processor component known as Software Guard Extensions, or a "secure enclave." SGX is a sequestered portion of a processor that runs code like any other, but the software inside it can't be accessed or changed by a device's broader operating system. Computers can still check that an enclave is running the right software to validate it before connecting, but neither MobileCoin users nor node administrators can decrypt and view the enclave.