July 9 (Reuters) - Square Inc (SQ.N) will make a hardware wallet for bitcoin, the payments company confirmed in a tweet on Thursday shortly before U.S. Senator Elizabeth Warren flagged growing risks posed to consumers and financial markets by the cryptocurrency market. Bitcoin wallets can be stored offline or online at cryptocurrency exchanges, venues where bitcoin can be bought and sold for traditional currencies or other virtual coins. With a non-custodial wallet, you have sole control of your private keys, which in turn control your cryptocurrency and prove the funds are yours. With a custodial wallet, another party controls your private keys. Most custodial wallets are web-based exchange wallets. "We have decided to build a hardware wallet and service to make bitcoin custody more mainstream...", Jesse Dorogusker, head of hardware at Square said in a twitter thread. Many companies have emerged to serve a growing need to protect their assets from online theft. Last month, Chief Executive Officer Jack Dorsey hinted in a tweet that the company was considering creating a non-custodial hardware wallet for bitcoin. Dorsey is also the chief executive of Twitter Inc. read more Cryptocurrencies reached a record capitalization of $2 trillion in April, but U.S. oversight of the market remains patchy. Warren, a former U.S. presidential candidate, on Thursday raised concerns in a letter to Securities and Exchange Commission Chair Gary Gensler, in an effort that could help lay the groundwork for legislation to regulate the fast-growing cryptocurrency market. read more