By Hannah Lang Dec 12 (Reuters) - Crypto giants including Ripple and Circle on Friday received preliminary approval from a top ​banking regulator to establish national trust banks, in a ‌major move that could further integrate digital assets into the banking system. The Office ‌of the Comptroller of the Currency conditionally approved two new national trust bank charters from Circle and Ripple, and conditionally approved applications from BitGo, Paxos and Fidelity to convert state trust bank charters to ...