@@ -94,13 +94,14 @@ the owner may sell their property to multiple people and there would be no way
9494to determine who is the new owner. With the land registry, all you need to do is
9595ask the registry which sale happened first, and that's the one that counts.
9696
97+<a name="1"></a>
9798Again, Urbit is yours and it's forever. Trusting central registries
9899jeopardizes both. The keen reader will notice that the problem of determining
99100which key rotation happened first is exactly the double-spend problem that
100101Satoshi solved with his proof of work algorithm for Bitcoin. His first block
101102famously includes a newspaper headline to prove he didn't mine the block before
102103that date. In a beautiful duality, his own algorithm proves that he didn't mine
103−it after that date.[^1]
104+it after that date.<sup><a href="#f1">[1]</a></sup>
104105
105106Some argue that blockchain is only good for money. This is myopic and is
106107generally based on the experience that its most valuable application so far has
@@ -120,6 +121,7 @@ on the network will listen to the blockchain for key data. Thus, we have global
120121consistency, permanence, and self sovereignty. We know of no other solution
121122that can provide these properties.
122123
124+<a name="3"></a>
123125While small individually, the aggregate PKI data for all nodes on the
124126network may become very large. This is not an issue for comets because nobody
125127needs to store comet keys except for those which they're talking with, and even
@@ -128,7 +130,7 @@ is a canonical set of keys, and somebody must store that. There are about
1281302<sup>32</sup>, or 4 billion planets. If the PKI data is about 100 bytes for
129131each planet, this is about 400 GB of data. This may be more than most users wish
130132to store, but it's small enough that it would be very cheap for someone to host
131−this data for many users[^3].
133+this data for many users<sup><a href="#f3">[3]</a></sup>.
132134
133135This information is currently stored directly on the Ethereum 1.0 blockchain,
134136but as is well understood in blockchain circles this approach will not scale