They have both. Their original offering was indeed a centralized off-chain payment network, where they hold funds on behalf of everyone and just move coins in

They have both. Their original offering was indeed a centralized off-chain payment network, where they hold funds on behalf of everyone and just move coins in their own internal database. https://21.co/learn/21-micropayments/#off-chain-transactions-bittransfers https://21.co/learn/21-micropayments/#off-chain-transactions... What they released now is a trustless solution based on "real" bitcoin payments: https://21.co/learn/21-micropayments/#micropayment-channels https://21.co/learn/21-micropayments/#micropayment-channels (Note, however, that this exists for nearly two years as part of BitcoinJ and other libraries... https://news.ycombinator.com/item?id=11100518 https://news.ycombinator.com/item?id=11100518)