NEW: Blockchain startup Alta raised $47.5 million in a Series A funding round led by Index Ventures, with participation from Google Ventures, Blackbird Ventures, Square Peg and Capital49, Fortune reports. The company is developing a Layer 1 blockchain designed for banks and large financial institutions, with built-in privacy and compliance tools, and counts Australian fintech firm Airwallex — which led its $32.5 million seed round — as a key backer and distribution partner.