MobileCoin Review: The Signal Integrated Privacy Coin

Last updated: Mar 30, 2023
18 Min Read
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Since its earliest days cryptography has been used to secure communications. It began with simple encoded messages, and has evolved to more complex digital interactions such as we see in various blockchain projects today.

And of course along with the blockchain we’ve also been gifted with cryptocurrencies as one offshoot of cryptographic technology. This allows people to transfer value while maintaining surety that there is no falsification or counterfeiting of any currency or transactions.

Those without limited or no knowledge of cryptographic protocols might think that any digital transaction needs to be sent textually to make it publicly verifiable, simply because this is what they are used to.

However, cryptographic communications on blockchains can very definitely conceal the identity of participants and can even obscure the amounts involved in transactions, while still allowing the transactions themselves to be verified. This is exactly the methodology used by the cryptocurrency called MobileCoin.

MobileCoin Logo
MobileCoin is made for mobile devices. Image via 

MobileCoin was created as a decentralized digital payment network. Its goal is to enable the exchange of value in a safe and efficient manner. Like any other cryptocurrency you might be familiar with, MobileCoin also creates and maintains an immutable transaction record in its blockchain. Most interestingly, MobileCoin has been optimized for use on mobile devices and on messaging platforms.

In December 2020 the mainnet went live and the project is now testing its functionality as a transactional cryptocurrency being used on a messaging app.

What is Mobile Coin

MobileCoin released a whitepaper in 2017, which was written by current CEO Joshua Goldbard and advisor and Signal founder Moxie Marlinspike. The company MobileCoin was founded in 2018 and is based in San Francisco, but holds its corporate registration in Delaware. The project aimed at providing fast and easy payments to mobile.

According to the whitepaper, the motivation for the project was to:

develop a fast, private, and easy-to-use cryptocurrency that can be deployed in resource constrained environments to users who aren’t equipped to reliably maintain secret keys over a long period of time, all without giving up control of funds to a payment processing service.

Mobile Coin went live in December 2020 and is described on its website as “a cryptocurrency designed to be used as digital cash on your phone. It's easy to use with near instantaneous transactions,” which is a simpler way of stating the goal that was originally put forth in the whitepaper.

Key Features

  • Easy wallet recovery
  • Fast transactions
  • Privacy
  • User-friendly and planet-friendly

How Does Mobile Coin Work

MobileCoin is using a number of novel techniques, however many of those are backed by technical documentation that does not address key details that might be considered pertinent to MobileCoin, or by papers that have not been peer reviewed and are either incomplete or contain errors.

Some other areas of the technical workings can only be understood by examining the source code and documentation directly. And honestly, if you don’t have a background in mathematics you can’t be expected to understand the intricacies of elliptic curve cryptography and advanced Schnorr-like signatures, which are used extensively by MobileCoin.

Cryptocurrency for everyone, but still very complex under the hood. Image via Mobilecoin.Foundation 

The following review will attempt to simplify the workings of MobileCoin, and will go into some of the more practical elements of the project, such as its current implementation and usage.

Those interested in digging into the depths of the technical documentation are free to check out The Mechanics of MobileCoin, a comprehensive technical explanation of MobileCoin that has been commissioned by the MobileCoin Foundation, and was recently released on GitHub by the psuedoanonymous developer koe.

That work introduces the fundamental concepts necessary to understand elliptic curve cryptography, reviewing algorithms and cryptographic schemes, and collecting in-depth information about MobileCoin’s inner workings. It is presented as a step-by-step description of the MobileCoin cryptocurrency, and at 144 pages long we do believe it is quite comprehensive.

The writer koe has assumed that many readers will come to the document with little or no knowledge and understanding of discrete mathematics, algebraic structures, cryptography8 , or blockchains. In that regard the book was written to be thorough enough that laypeople with a diversity of backgrounds may learn about MobileCoin without needing external research.

A Basic Understanding of MobileCoin

MobileCoin is designed so that a mobile messaging application like WhatsApp, Facebook Messenger, or Signal can integrate with a MobileCoin wallet.

Private Payments Simplified
Fast, secure, and private. Image via 

MobileCoin was developed using the Stellar Consensus Protocol, which is a Proof of Reputation protocol. The intention of the developers was to create an end-to-end encrypted ecosystem similar to the messaging apps Signal and WhatsApp, both of which use the Signal protocol that was developed by Marlinspike.

It’s important to note that the Stellar Consensus Protocol is not the same as the Stellar Network. While the Stellar Network runs on the Stellar Consensus Protocol, it is a separate implementation to that used by MobileCoin. However, MobileCoin does use the Stellar blockchain because of its speed and efficiency.

The consensus model used by MobileCoin is Byzantine Fault Tolerant, and it copies that used by Stellar. That means the verification nodes used must be approved by the MobileCoin Foundation.

Furthermore, these nodes must run on a machine that’s been build using the Intel SGX chipset which offers hardware-based memory encryption that isolates specific application code and data in memory. Interestingly there is no mention anywhere of a staking requirement to run a node, or of any incentive rewards for those running nodes.

According to the MobileCoin whitepaper:

A user should be able to install the app, enter a 4 digit PIN, and send/receive funds to/from other users addressed by their phone number or other user identifier. Transactions should take less than a second, funds should be immediately available for use, and neither the messaging service nor any other third-party should learn anything about a user's account balance or transaction history (such as who is paying who). At any point, a user should be able to reinstall the app or get a new phone and regain secure access to their funds simply by entering a 4-digit PIN. Payments should also be possible across apps and networks.

The developers of MobileCoin also understand that one of the key challenges of any cryptocurrency or blockchain project is usability. According to MobileCoin advisor Marlinspike in a December 2017 Wired article:

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.

Don't confuse the Stellar Consensus Protocol with the Stellar Network. Image via 

By using the Stellar Consensus Protocol, the validating nodes don’t necessarily store the full transaction history of the blockchain. Instead they discard most data after each transaction is completed. This makes MobileCoin more resistant to surveillance, whether it’s coming from a government or a criminal who wants to track and extort users.

Privacy & Fungibility

Cryptocurrencies used a distributed ledger called the blockchain to store the information about all the transactions that occur with those currencies. In most cases this information is stored in plain text, because this makes is easier for the community to verify the existence of transactions. This clearly defies any concept of privacy or fungibility since it is publicly posting the complete transaction history of all users.

Privacy and fungibility are more important than most people think. Image via Pinterest 

Thus users of cryptocurrencies like Bitcoin have found ways to restore their privacy by such means as using temporary intermediate addresses when conducting transactions. However this is far from perfect as the true senders and receivers can still be revealed through the analysis of coin flows.

MobileCoin is addressing the issue of privacy by storing single use addresses for the ownership of assets, and then authenticating the use of those assets with ring signatures and verifying transactions using secure enclaves that act as black boxes which discard any extraneous information after verification is completed. This completely avoids the possibility of another person analyzing transactions to link senders with receivers.

In addition, MobileCoin renders all currency flows opaque by concealing transaction amounts behind cryptographic constructs. The end result is a currency that exhibits high degrees of both privacy and fungibility.

MobileCoin and Signal

The encrypted messaging service announced on April 6, 2021 that they began testing a peer-to-peer payment system as a beta in its app in some jurisdictions. The new service is being called Signal Payments and the new feature only supports the MobileCoin wallet and the cryptocurrency MOB.

Of course signal was co-founded by its CEO Moxie Marlinspike, and it has a close relationship with MobileCoin as Martinspike is publicly acknowledged as an advisor to the MobileCoin project.

The first payments protocol we’ve added support for is a privacy focused payments network called MobileCoin, which has its own currency, MOB,” wrote Jun Harada, Signal’s head of growth and communication, in a blog post.

Signal claims that it chose MobileCoin over Zcash or Monero because MobileCoin was specifically designed for use with mobile devices. While Signal is cross-platform, the bulk of its users are on mobile devices. It is known that mobile devices struggle with many blockchains since they are not able to store large amounts of data, and when using mobile devices the blockchain transactions are handled differently.

We want payments in Signal to be fast, private, and work well on mobile devices. The first payments protocol we’ve added support for is a privacy-focused payments network called MobileCoin, which has its own currency, MOB. – Signal official announcement

Due to the design of MobileCoin the Signal app never has access to a users balance, transaction history, or funds. And of course users are able to transfer their MOB coins off the Signal app and into another app or service at any time. Because of MobileCoin’s design it is likely it will be implemented in other messaging apps in the future if the beta test on Signal works well.

In addition, if the use of MOB over Signal and other messaging apps becomes commonplace it could revolutionize the use of cryptocurrency.

MobileCoin Signal
MOB usage on Signal. Image via Signal blog. 

Signal is not as popular as other messaging apps like Telegram or WhatsApp, but it has been growing and has strong advocates such as Elon Musk and Edward Snowden who could help popularize the app further. While Signal does not disclose the size of its user base, it’s been estimated that it is around 40 million users. That compares with Telegram’s 500 million users and WhatsApps 2 billion users.

Future Uses

Because MobileCoin is quite new as a cryptocurrency, and the payment system on Signal is in a limited beta there has been little talk of future enhancements, however it has been suggested that just as any other blockchain based on the CryptoNote protocol MobileCoin will be able to support second layer extensions, multisignature, transaction proofs, escrowed marketplaces, and much more.

Historical Problems with Regulators

It’s well known that messaging apps and cryptocurrencies together haven’t been well received by regulators. Both Kik and its KIN token and Telegram have had drawn out battles with the SEC, with both eventually choosing to forego adding cryptocurrency support to their messaging apps. However MobileCoin might be safe since it’s backed by venture capitalists and hasn’t been funded via ICO like Kik and Telegram.

SEC and Kik
Regulators don't like crypto payments over messaging apps. Image via ZDnet 

Telegram chose to shut down its own cryptocurrency project in 2020 after battling regulators for several years. Prior to that they were planning on issuing a GRAM token that could be used on Telegram for the fast, secure transfer of value.

It seems like the most difficult jurisdiction for regulation is the U.S. and so far Signal is avoiding that market. There’s even a notice on the MobileCoin Github warning that the MobileCoin Wallet is not available for download or use by U.S. persons or entities, persons or entities located in the U.S., or persons or entities in other prohibited jurisdictions.

MobileCoin & Signal Controversy

While it has been acknowledged that Signal co-founder Moxie Marlinspike is an advisor to MobileCoin, it turns out there could be a closer relationship between the two projects. An early copy of the MobileCoin whitepaper dated November 13, 2017 lists Marlinspike as the CTO of MobileCoin. That would most likely mean that the integration with Signal is simply a method to monetize the large Signal userbase.

Moxie Marlinspike
Signal founder Moxie Marlinspike might have also helped create Mobilecoin. Image via Yahoo! Finance 

However other versions of the whitepaper also appear online and do not include a section on the MobileCoin team members. MobileCoin CEO Joshua Goldbard in 2017 denied that Martinspike was ever the CTO of the project, and that the whitepaper with the team members is nothing written by anyone at Mobilecoin.

There are also snapshots of the MobileCoin website from December 2017 through April 2018 that list Martinspike as a member of “The Team”, however it does not give him a title. In May 2018 his title was finally listed as Advisor.

Moxie was never CTO. A white paper we never wrote was erroneously linked to in our new book, ‘The Mechanics of MobileCoin.’ That erroneous white paper listed Moxie as CTO and, again, we never wrote that paper and Moxie was never CTO.

This book is actually the most recent “comprehensive, conceptual (and technical) exploration of the cryptocurrency MobileCoin” posted on the MobileCoin Foundation GitHub, which Goldbard describes as project’s “source of truth” and serves as the most up-to-date technical documentation for the project.

The team has always acknowledged Martinspike as an advisor to the project, but never discussed any direct involvement in MobileCoin, and certainly nothing as involved as the role of CTO.

Of course if Martinspike was the CTO at MobileCoin, or held a more involved role than that of advisor it raises questions regarding the motivation for aligning with the project.

Signal sold out their user base by creating and marketing a cryptocurrency based solely on their ability to sell the future tokens to a captive audience,” said Bitcoin Core developer Matt Corallo, who also used to contribute to Signal’s open-source software.


You can check the current team of MobileCoin on LinkedIn. There are 27 members listed, including CEO Joshua Goldbard, although he lists his title as “Janitor”, not CEO. Working in Telecom for much of his adult life, Joshua developed, managed, and implemented networks of significant complexity. His expertise on mobile systems as well as his passion for cryptocurrency as an information network governing systems of value help him lead this project.

The current CTO of MobileCoin is Sara Drakeley Hall, and while she’s been with MobileCoin since 2018, she’s only been in the position of CTO since February 2021. She brings a wealth of technical experience to the project, having worked as a technical director at Walt Disney Animation Studios and as a software engineer at SpaceX.

Sara and Josh
CTO Sara Drakeley Hall and CEO Joshua Goldbard. Image via Mobilecoin Foundation blog. 

Chief Architect for MobileCoin is Matthew Faulker, a PhD computer scientist with a specialty in algorithms and systems for understanding the physical world through IoT devices.

And the VP of Engineering for MobileCoin is Toby Segaran, who brings more than two decades of experience to MobileCoin. He was previously Senior Director of Engineering at Reddit as well as a staff software engineer for Google.

MobileCoin Token (MOB)

The MOB token was created with a maximum supply of 250 million tokens which were pre-mined. Currently there is no data on circulating supply however as there is no blockexplorer for MobileCoin. It is only listed on a handful of exchanges too, which makes it more difficult to acquire.

As of April 2021 you can trade for MOB tokens on FTX, Bitfinex, BigONE, and Hotbit. Notably missing from that list is Binance, which is unusual since Binance was an early investor in MobileCoin back in 2018. It was also the lead in the crowdfunding round for the coin.

At the time Binance released the following statement:

As one of the market leaders in the space, our mission at Binance Labs is to help advance blockchain technologies and grow our collective crypto ecosystem. A mobile-first, user-friendly cryptocurrency, like MobileCoin, plays a critical role in driving mainstream cryptocurrency adoption. The MobileCoin team and Binance Labs share a common vision and we are proud to be a supporter of what they are doing.

With such an association between Binance and MobileCoin it only makes sense to presume they will list the MOB coin at some time, likely in the near future.

As far as pricing for the MOB token goes, that’s been nothing less than spectacular in 2021. In the prior year MOB traded around the $2 level, but heading into 2021 it had already doubled to $4. In late March 2021 the price suddenly catapulted to $18 and within three days MOB closed March out at $39. It’s likely there was some knowledge regarding the upcoming announcement of the Signal integration.

MOB Chart
The rapid rise of MOB. Image via 

On April 6, 2021 Signal announced the addition of MOB to its platform, and on the same day MOB hit an all-time high of nearly $70. Since then the price has dropped, but as of April 15, 2021 it remains at $54.92.


Putting aside the controversy over whether or not Moxie Martinspike was ever the CTO of MobileCoin, which will likely never be answered, the idea of MobileCoin is an excellent one. And the implementation seems well thought out too.

After all, it seems clear that digital currency will eventually replace physical currency for most uses. And with so many people carrying smartphones it only makes sense to create a currency that can be transferred quickly and easily via a mobile app.

There are still a number of questions that need to be addressed however. Will MobileCoin deliver on its promise of fast, secure money transfer? Will users actually embrace the use of cryptocurrency within messaging apps?

The most important question at this time is whether the project will remain ahead of regulators or if it could suffer the same fate as Kik and Telegram.

It’s still early days for MOB, but so far things are looking promising. We recommend keeping an eye on the project to see how it develops over time.

Steve Walters

Steve has been writing for the financial markets for the past 7 years and during that time has developed a growing passion for cryptocurrencies.

Disclaimer: These are the writer’s opinions and should not be considered investment advice. Readers should do their own research.

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