The concept of broadcasting Bitcoin transactions over radio transmissions has been around for several years. In 2017, the notion was expanded on in a proposal by crypto pioneer Nick Szabo and Elaine Ou detailing the benefits that radio transmissions using shortwave frequencies could have on Bitcoin’s network resilience.
Recently, TxTenna launched, enabling offline Bitcoin transactions through a collaboration of GoTenna — the radio mesh network communication company — and Samourai Wallet, the privacy and security-focused Bitcoin wallet.
Mainstream media understanding of Bitcoin is still underwhelming, so it is not surprising that offline Bitcoin transaction capabilities have flown under the radar. However, they represent an intriguing and compelling opportunity for off-grid broadcasts of signed Bitcoin transactions. Essentially, Bitcoin’s network infrastructure does not need to be in place for nodes to interact. The future implications of this are considerable and can have a particularly positive effect in disaster areas and political regimes where censorship is ubiquitous.
Understanding How Weak-Signal Radio Communications for Bitcoin Work
Szabo and Ou’s proposal outlines weak-signal high-frequency radio waves as a mechanism to increase the multi-homing of the Bitcoin network. By increasing the diversity of node connections, the network can become much more resilient, which enables a more isotropic (i.e., trust-minimized) network.
The direct goals of such a model are to reduce potential modification problems associated with mesh relays, enable censorship-resistant participation (The Great Firewall of China does not stop radio broadcasts), allow participation of SPV nodes without Internet connections, and provide the ability to select a more diverse access structure set.
TxTenna employs Ultra High-Frequency (UHF) radio waves as part of GoTenna’s already established UHF radio mesh network that was originally designed for communication in remote or disaster areas. UHF radio waves are primarily propagated through line-of-sight, meaning they are blocked by mountains, large hills, buildings, and other significant obstacles. However, they are commonly used in television broadcasts, walkie-talkies, and GPS. They are typically used for local region communication as they have a shorter range than other available methods.
UHF radio broadcasts from GoTenna devices work in a P2P mesh network where a node sends out a signal looking for other nodes nearby with the intention of finding the intended recipient. If the recipient is not directly found, the node sends out a burst broadcast within its range (~ 0.5 – 4 miles) to find other nodes. Nodes use the network’s routing protocol to determine the optimal route to reach the intended recipient and then remember the defined path between the two communicants.
TxTenna utilizes the same functionality of GoTenna’s mesh network with a slight optimization. The GoTenna device connects to the Samourai Wallet, and then sends a UHF radio signal looking for peers. However, the transmission is searching for an Internet-connected GoTenna device rather than an intended recipient through the UHF radio mesh network. Transactions can be broadcast directly from the Samourai Wallet app which then hops between GoTenna devices until the broadcast finds one that is connected to the Internet.
The initial transaction — broadcast from a device not connected to the Internet and through UHF radio wave to the GoTenna mesh network — is subsequently confirmed on the Bitcoin blockchain by the online TxTenna (GoTenna) user that automatically broadcasts the transaction to the regular (Internet-connected) Bitcoin network. A private confirmation message is then relayed back to the original TxTenna transaction sender. Essentially, a user can send a Bitcoin transaction without being connected to the Internet.
Samourai Wallet is also one of the most privacy-conscious Bitcoin wallets out there, implementing advanced schemes such as Stonewall, Richochet, and PayNyms to augment user privacy and security.
GoTenna devices are widespread too. There are more than 100k GoTenna devices sold, and their mesh network nodes are sprawling in diverse locations across the U.S. and Europe. Eventually, the proliferation of UHF radio off-grid Bitcoin transactions could become common, increasing the capacity of the mesh network and feasibility for regular users to send transactions through such a medium.
Benefits and Future Potential of Off-Grid Bitcoin Transactions
The direct benefits of UHF off-grid Bitcoin transactions — such as with TxTenna — are straightforward and promising. Restrictive ISPs and mobile carriers can be subverted, multiple hops through TxTenna devices obfuscate your physical location and SIM identifiers, and air-gapped Bitcoin broadcasts are enabled. Moreover, data packets sent through a mesh network are not retained by relayers, only the intended recipient.
The repealing of net neutrality by the U.S. Federal Communications Commission earlier this year has also led to a surge in interest around mesh networks and radio broadcast technologies. Where services like TxTenna can really make a substantial impact — even now — is in oppressive regimes where censorship resistance is widespread and severe.
For instance, users of TxTenna in China could broadcast transactions through a TxTenna/GoTenna mesh network device without connecting to the Internet, substantially improving their privacy by subverting the Great Firewall of China (GFC). The potential of the GFC under China’s government to deanonymize users of Bitcoin was explicitly outlined in a recent report produced by a collaborative effort of Princeton and FIU.
Off-grid Bitcoin transactions also have enormous potential for disaster-stricken areas, as recently seen in Puerto Rico with Hurricane Maria. Minimal access to the Internet effectively removes any notion of online banking and flexibly exchanging value. Sending Bitcoin transactions through UHF radio frequency — where TxTenna nodes could even be set up in an emergency relief response — has the potential to allow natural disaster victims to receive funding from family members abroad or charitable donations without needing the requisite network infrastructure.
Technologies that increase Bitcoin’s network resilience are not just relegated to UHF radio mesh networks either. Blockstream has been researching and developing a satellite network for broadcasting the Bitcoin blockchain worldwide 24/7 for the opportunity for everyone in the world to use Bitcoin and assist in overall network protection and resiliency. Blockstream Satellite reduces Bitcoin’s dependence on the Internet, lowering barriers to entry and further increasing multi-homing of the network.
As Bitcoin continues to develop, enhanced privacy features are emerging left and right. TxTenna and UHF radio wave off-grid transactions are assuredly a much different approach than protocol enhancements but nonetheless, are vital improvements. The infrastructure for functional mesh networks (i.e., sufficient UHF nodes) is relatively only available in several developed areas in the world like the U.S. and Europe, currently. However, the potential for that to change rapidly is real. A growing multi-homing Bitcoin network as outlined by Szabo and Ou offers a dynamic view of the future potential of Bitcoin’s resilience and perhaps a glimpse into its future network topology.