[Bitcoin-development] Draft BIP for seamless website authentication using Bitcoin address

Mike Hearn mike at plan99.net
Fri Apr 4 13:43:13 UTC 2014

On Fri, Apr 4, 2014 at 3:22 PM, Eric Larchevêque <elarch at gmail.com> wrote:

> I see only benefits for the entire ecosystem, and if I'm working on such a
> proposition it is because I really need this feature.

Why do you need it? Because you don't want to implement a login system?
Very, very few websites are the sort of place where they'd want to
authenticate with only a Bitcoin address. If for no other reason than
they'd have no way to email you, and if you lost your wallet, you'd lose
all your associated data.

> Without such a standard protocol, you could never envision a pure Bitcoin
> physical locker rental, or booking an hotel room via Bitcoin and opening
> the door through the paying address.

In future there often won't be a simple paying address. For instance, if my
coins are in a multi-sig relationship with a risk analysis service, there
will be two keys for each input and an arbitrary number of inputs. So does
that mean the risk analysis service gets to open my locker? Why?

What if I do a shared spend/CoinJoin type tx? Now anyone who took part in
the shared tx with me can get into my hotel room too?

These are the kinds of problems that crop up when you mix together two
different things: the act of paying, and the act of identifying yourself.
You're assuming that replacing a password people can remember with a
physical token (their phone) which can be stolen or lost, would be seen as
an upgrade. Given a choice between two physical lockers, one of which lets
me open it with a password and one of which insists on a cryptographic
token, I'm going to go for the former because the chances of me losing my
phone is much higher than me forgetting my password.

All the tools you need already exist in the form of client certificates,
with the advantage that web servers and web browsers already support them.
The biggest pain point with them is backup and cross-device sync, which of
course wallets suffer from too!
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