When does a company actually control customer bitcoins?

Cryptocurrencies like Bitcoin give us the tools to create all sorts of new financial relationships. They make it possible for individuals to be their own bank, and make it easier for companies to provide bank-like services. With multi-sig and n-lock transactions (both explained herein), even more arrangements emerge: divided custody of funds, delayed custody, custody contingent on the revelation of a secret or the solution to a puzzle. With these complexities in mind, when does a company actually have control of their customer’s bitcoins? When, alternatively, is a company merely providing a non-custodial service like software design, back-up key recovery, or escrow?

To outline this question and help provide some answers, we’ve prepared the following plain English slide deck that explains: