A startup developing uses of the technology underlying bitcoin for trading derivatives has hired a former senior banker and Citadel executive as its chief operating officer.

Thomas Chippas, who was chief executive of Citadel Technology, recently joined Axoni after leaving the Chicago investment firm in January. Mr. Chippas, 45, also was previously a managing director at Barclays PLC and Deutsche Bank AG working in trade execution and financing.

He joined Axoni this week to help build up the young firm, which this year separated from TradeBlock, itself a startup that provides trading services for the bitcoin digital currency, according to Axoni chief executive Greg Schvey.

Axoni has been working with big banks and trading firms to settle over-the-counter trades using the blockchain, or the underlying technology that was developed for settling bitcoin trades using a shared global network.

Last month, Axoni unveiled a successful test of credit derivatives trading involving J.P. Morgan Chase & Co., Credit Suisse Group AG, the Depository Trust & Clearing Corp., and Markit Ltd. In March, Axoni said it had worked with ICAP PLC to test the use of blockchain for large foreign exchange trades.

Axoni, which currently has just nine employees, plans to add many more in the near term, Mr. Schvey said. He wouldn't comment on additional fundraising efforts.

A number of former bankers have joined blockchain-focused companies in the past two years, including Blythe Masters, the former global head of commodities at J.P. Morgan, who joined Digital Asset Holdings LLC as chief executive last year.

The moves follow a broader shift in attention from bitcoin, the controversial currency embroiled in disagreements about its founding and usage, to the core technology that enables it.

A group of startup firms, also including itBit Trust Company LLC, R3, Symbiont.io, will be vying for contracts at banks and other financial services companies to implement blockchain-based technologies.

However, they will also face pressure from bank regulators and other intermediaries who will look to preserve their role in the financial system and closely monitor the new technology.

Banks have been testing applications of blockchain as a way to replace existing systems that require each party to a trade plus a central clearinghouse to record the trade. Blockchain-based networks can allows banks and regulators to share a single record of a trade over a network.

Before Citadel, where he ran the unit that sells investment management technology to clients, Mr. Chippas worked with trading clients at Deutsche Bank and Barclays to execute and fund complex computer-driven trades.

"We're at the same inflection point we were in the early 2000s" with electronic trading protocols, said Mr. Chippas in an interview. Blockchain technology "can redefine how firms interact with each other."

Write to Telis Demos at telis.demos@wsj.com