Coinbase, the largest cryptocurrency exchange in the United States, reported a 63 percent decline in revenue on Tuesday, as it weathers a broader downturn in the crypto market.The company said revenue for the second quarter was $808 million, down from $2.2 billion a year earlier. Its number of monthly customers rose to nine million from 8.8 million last year, but it was down from 9.2 million the previous quarter. Coinbase also swung to a net loss of $1.1 billion, compared with profits of $1.6 billion a year ago.