San Francisco-based payments processing company Square has reportedly decided to open-source its Bitcoin cold storage technology, which is designed to support trading through its Cash app, the company’s peer-to-peer mobile finance service.
The news comes from a blog post published on October 23rd, announcing that the source code, software development kit (SDK), and documentation for the company’s cold storage solution is now accessible on Github’s repositories.
As Square’s software engineer Alok Menghrajani noted in a blog post, the company chose to make the system open source aiming to encourage further innovation in the cryptocurrency space, as well as to provide companies with a higher security level:
“We hope that by sharing our work, we can make it easier for others to fulfill their security needs, enabling even more innovation — and better protection for all players — in the cryptocurrency space. In the long run, since we had to solve problems that other companies may face, we are interested in standardizing some of our work.”
Cold storage is defined as a means of keeping cryptocurrency holdings and users’ private keys offline in order to prevent the possibility of theft via a remote attack. The Square solution is called Subzero and represents itself an enterprise offline Bitcoin wallet, which is beneficial for “those who don’t want to use an off-the-shelf hardware wallet because they need to create unique customizations or implement business-related rules”.
Subzero relies on Hardware Security Modules (HSMs), which are specialized hardware devices commonly used for storing sensitive cryptographic key material and performing operations with those keys. Square has recently released the code, documentation, and tools for the Subzero’s HSM-backed cold wallet.
According to Menghrajani:
“Funds can be sent from online systems to the cold storage at any time. Moving funds out of cold storage requires a multi-party signing ceremony. In addition, the offline HSMs are able to enforce business logic rules, for instance we only allow sending funds to Square-owned addresses. Such a scheme is usually called defense in depth or an onion model. We maintain the online/offline isolation by importing transaction metadata and exporting signatures using QR codes.”
Moreover, Square is also open-sourcing its Beancounter tool, designed for auditting wallet balances. Among the most notable features of Beancounter are the abilities to compute the balance at any given date in the past, and to handle wallets with very large number of transactions.
Square Inc. was founded in 2010 by the 41-year-old billionaire, Jack Dorsey, who is also the CEO of Twitter. Initially, it was only a small business platform that allowed users to make payments using credit or debit cards from their smartphones. In November of 2017 the company began supporting Bitcoin trading through its Cash app. In mid-August, Square’s Cash app officially let users buy and sell bitcoin in all 50 US states.