Coinbase CEO Brian Armstrong denies selling 'paper Bitcoin' to BlackRock and addresses concerns over transparency and reserves.Armstrong clarifies that the minting and burning of Bitcoin for BlackRock's spot Bitcoin ETF are conducted transparently and on-chain.Coinbase CEO emphasizes that Deloitte audits the company annually, offering public verification of results.Concerns also raised regarding Coinbase's wrapped Bitcoin product, cbBTC, with questions about backing and reserves.