(CNN) — Senate Banking Committee members don’t trust Facebook. That was a main takeaway from Tuesday’s Senate Banking Committee hearing on Facebook’s Libra cryptocurrency. Because of that, they have serious concerns about Facebook’s entrance into the largely unregulated cryptocurrency market.

Many lawmakers questioned Facebook executive David Marcus about why people should trust the company to manage their money and why they should trust Facebook to lead the way on a major new fintech regulation that could fundamentally change global financial systems.

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“Facebook’s motto is move fast and break things,” Sherrod Brown, the Committee’s senior member, said. “They’ve moved fast and are helping to undermine our democracy. Now they’re expecting us to trust them with our paychecks.”

Marcus’ answer, in large part, was that no one necessarily has to trust Facebook itself.

Marcus, who heads up Libra, stressed the company will be only one of what it hopes will eventually be 100 members of the Libra Association, the governing body that will manage the currency. And he also said the vision is for consumers to have many options for tools to use Libra from trusted companies, not just Facebook’s Calibra wallet. From there, he said, Facebook “will have to work hard to earn people’s trust” in its own products.

The often tense exchanges between lawmakers and Marcus illustrated the challenges Facebook will face as it attempts to launch the digital currency, which it has hoped to do by early 2020. Wednesday, Marcus will face more questioning from the House Financial Services committee. Lawmakers want to understand more about Libra and its implications both for consumers and global financial systems.

Marcus wants to convince them of the digital currency’s potential benefits and Facebook’s willingness to work with regulators on its implementation.

“I expect that this will be the broadest, most extensive and most careful pre-launch oversight by regulators and central banks in FinTech’s history,” Marcus said in his opening remarks.

This set of lawmakers has been trying to understand Libra for some time. Weeks before the official Libra announcement, with rumors of the plans swirling, the Committee sent Facebook a letter requesting information on how Libra would work and how users’ data would be protected.

Facebook said it met with lawmakers and regulators in the lead-up to the announcement, including with Federal Reserve Chairman Jerome Powell.

Brown has repeatedly criticized Facebook’s plans for Libra. He said last week the currency could pose a “threat to our democracy” if it were to become such a widely used medium of exchange that it compromised the Fed’s ability to enact monetary policy.

“They’re motivated by one thing: surely their own bottom line,” Brown said last week. “Allowing Big Tech companies to take over the payment system or position themselves to influence monetary policy would be a huge mistake.”

But Facebook says Libra and the Libra Association will not aim to supplant the Federal Reserve or any other central bank.

“The Libra Association … has no intention of competing with any sovereign currencies or entering the monetary policy arena,” Marcus said.

Many senators opened their remarks by mentioning concerns about user privacy and data security.

Facebook has said it established Calibra as an independent subsidiary within the company to develop its digital wallet and other products to use Libra. The company says Calibra will not share users’ financial data with Facebook, except under limited circumstances such as for fraud mitigation. The two will also share financial data if users agree to it, though it is unclear how it will ask users for their consent.

What is Libra?

Libra is a cryptocurrency developed by Facebook. The company says Libra will make sending money online cheaper and faster, and it will improve access to financial services, especially for people without bank accounts or with little access to banking.

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How will Libra work?

Libra and the technologies to use it will be built upon a blockchain platform called the Libra Network.

A blockchain is made up of a series of servers (also called “nodes”) that record and validate every transaction made on the network. Unlike with many other cryptocurrency networks that allow any server to join the chain, the Libra Network is a “permissioned” blockchain, meaning only certain servers will be able to connect to the chain.

Facebook says that will allow the network to run faster than other cryptocurrencies, making Libra practical for everyday uses like purchasing something online.

The network is built with open-source code, meaning any developer will be able to create a digital wallet or other tool to use Libra on top of the network. Facebook has said it will eventually transition the Libra network to a public blockchain, though it has provided no details on that process.

Who will oversee Libra?

Though Facebook envisioned and developed the infrastructure for Libra, it will not manage the digital currency. Instead, an independent, nonprofit organization called the Libra Association will oversee Libra’s launch and govern the currency.

The Libra Association is a consortium of companies and nonprofits from around the world based in Geneva, Switzerland. It has 28 founding members — including payments, technology, telecommunications, venture capital and blockchain companies, as well as nonprofit organizations. Members include Paypal, Lyft, Coinbase and Mercy Corps, among others. The association hopes to have 100 members by Libra’s launch.

The association will have two main roles: Member organizations will operate the servers to run the Libra Network, and the Libra Association will manage the reserve that will back Libra to ensure its stability.

How will Libra remain stable?

Facebook says Libra’s value will be less volatile than that of Bitcoin because it will be backed by real currencies. But unlike some other “stablecoins,” Libra’s value will not be fixed to any single physical currency (cryptocurrency exchange Coinbase, for example, offers a stablecoin backed 1:1 by US dollars).

Instead, Libra will be backed 1:1 by a reserve “basket” of fiat currency bank deposits, including the dollar, euro and Japanese yen, and government securities. This means its value relative to any one currency will vary.

What is Calibra?

Calibra is a Facebook subsidiary created to develop products and provide financial services using Libra.

The division’s first product will be the Calibra Wallet, a digital wallet that will let users store Libra and send it to friends like they’d send a text message at “low-to-no-cost,” Facebook says. The Calibra Wallet will be a standalone app, and will plug-in to Facebook’s Messenger and WhatsApp. Other companies and entities will also be able to develop wallets and other tools to use Libra on the network.

To protect user privacy, Facebook plans to keep the Calibra subisidary independent. The company says Calibra will not share customers’ account information or financial data with Facebook except in limited circumstances such as preventing fraud or complying with the law, or unless users have agreed to the sharing of their data.

What’s in it for Facebook?

Facebook expects Calibra will enable more transactions between users and businesses on its platforms, which could generate more ad revenue for Facebook. The company hopes to eventually offer more financial services and create new revenue streams through Calibra.

Facebook says it will not use Calibra users’ data for ad targeting.

What are critics saying?

Lawmakers and regulators are concerned about a new financial tool that will suddenly be available to Facebook’s 2.4 billion users, and they are scrambling to determine how to oversee it. Facebook will attend two public Congressional hearings this week, to evaluate Libra’s potential impacts on consumers and global financial systems. Some haveproposed legislation to stop Libra altogether.

In a press conference Monday, Treasury Secretary Steven Mnuchin said the government is worried Libra could be used for human trafficking, purchasing illegal drugs and other illicit uses. Last week, Federal Reserve Chairman Jerome Powell told Congress Libra “raises many serious concerns regarding privacy, money laundering, consumer protection and financial stability.”

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Facebook said it is willing to delay its entrance into the cryptocurrency market to work with regulators, though that may not stop the Libra rollout altogether