Re: Real BTCR DID Document

Dave Longley and Joe Andrieu,

In the simplest BTCR establishing transaction, a single key can do
everything. Both of these refer to the same key, but give them different
names (#satoshi will always be mutated to the whatever the key is in the
current spent bitcoin transaction, and #vckey-0 will be immutable and
future bitcoin transaction keys will increment the key name).

```
"authentication": ["#satoshi"],
"assertionMethod": ["#vckey-0"]
}
```

What other proof purposes should we add to this list? Any ideas on which
should be mutable (like #satoshi) or immutable but incremented (like
#vckey-0) and what those the key names should be?

Thanks!

— Christopher Allen