Facebook is keeping its cryptocurrency plans under wraps, even when it comes to other company employees.

The social media giant silos off its secretive cryptocurrency team in an office that requires entirely different key-card access so that other Facebook employees can't enter, according to a New York Times report, citing two Facebook employees.

Facebook's blockchain and cryptocurrency efforts are being run by former PayPal president David Marcus. It has been steadily building out its team, recently hiring a group of employees from blockchain start-up Chainspace. The tech giant hasn't publicly said what the team is working on. But Bloomberg reported in December that Facebook is looking to introduce mainstream users to digital currencies by allowing them to send money through WhatsApp, which Facebook owns.

The option would allow Facebook users to send money to friends and family instantly, the Times said, citing five people briefed on the effort. Facebook's cryptocurrency project is at the point that it has discussed selling "Facebook coin," to consumers with major cryptocurrency exchanges, according to the Times report.

Cryptocurrencies became a household name at the end of 2017. The investing mania was led by bitcoin, which rallied to nearly $20,000 by the end of 2017 after starting that year at less than $1,000. It has come crashing down 80 percent since, and was trading near $3,800 on Friday.

Bitcoin has largely failed as the type of currency people might use to buy a cup of coffee or instantly pay a friend. Its more popular use case is as a store of value, or "digital gold."

Projects by Facebook, Telegram, Signal, and other messaging apps would look to solve that speed-bump by making cryptocurrencies an accessible peer-to-peer payment, according to the report.

— Read the entire New York Times report here.