keys/hd/address.go
func CalcHash256(data []byte) []byte {
	return CalcHash(CalcHash(data, sha256.New()), sha256.New())
}
func CalcHash256(data []byte) []byte {
	return CalcHash(CalcHash(data, sha256.New()), sha256.New())
}
func CalcHash256 ( data [ ] byte ) [ ] byte { return CalcHash ( CalcHash ( data , sha256 . New ( ) ) , sha256 . New ( ) ) }
// CalcHash256 returns the sha256(sha256(data)).
CalcHash256 returns the sha256 ( sha256 ( data )) .