LONDON, Dec 19 (Reuters) - The world's biggest crypto exchange, Binance, is battling to shore up confidence after a surge in customer withdrawals and a steep drop in the value of its digital token.The exchange said it dealt with net outflows of around $6 billion over 72 hours last week "without breaking stride" because its finances are solid and "we take our responsibility as a custodian seriously."In an effort to look inside Binance's books, Reuters reviewed filings by Binance units in 14 jurisdictions where the exchange on its website says it has "regulatory licenses, registrations, authorisations and approvals.""We are a private company and are not required to publicize our corporate finances," he continued, comparing the exchange to privately-held firms such as U.S. candy maker Mars.PIECES OF A JIGSAW Binance's surge in outflows last week was attributed by analysts to concern over how crypto exchanges hold user funds and the Reuters report on the DOJ investigation."