David M., 44, created his first wallet on Thursday — a plain single-key setup, intended for "just a little, to try it out." Within the week he had a favourite block height and opinions about coin selection.

It is, by design, the simplest possible arrangement: one key, one wallet, no committee, no ceremony. The right tool for small amounts and first steps — the financial equivalent of a starter bicycle, before anyone has mentioned a vault.

David has since referred to the wallet as "my cold storage," "my stack," and, once, with feeling, "the family treasury" — in reference to roughly forty dollars.

Everyone starts with one key. The whole trick is knowing when one key is no longer enough.