The definition of blockchain is given on page 8 of the paper:

• A sidechain is a blockchain that validates data from other blockchains (0)

One may wonder how my sofa could possibly be a , since it (up to now) has no processing power or connection to the internet.

At first I thought of noting that my sofa's blockchain is stored in a spontaneously evolved quantum hypercomputer at the core of the Crab Nebula's neutron star, that uses quark exchanges for computation and polarized neutrino beams for input-output. More precisely, that it will be stored there three thousand years from now. Then, since that nebula is more than six thousand light-years away, Einstein's theory of relativity says that it also exists now.

But people might think that I was just making that up. And, of course, they would be right.

Fortunately, on checking the definitions of the paper, I was able to ascertain that my sofa's blockchain actually exists in the material sense: it is just the sofa itself!

Since the dev team of the sending chain C' cannot know who is the current holder of the asset A' in chain C'', the transfer must consist of at least two steps: the current holder h' in C' relinquishes its control over A', according to the protocol of C', to some entity p' of C' (that may be a script, address, etc.) that represents the sidechain C''; and notifies the network of C''. Then the network of C'' is supposed to create a corresponding asset A'' of that blockchain, under control of some entity p''.

The controlling entity p'' of C'' may be nominally given control to A' through p' (e.g. if C' is Bitcoin, p' may be an address and only C'', or some entity in it, may know the private key. But C'' must trust that C' will not take control away, and C' must trust that C'' will handle that key properly.

Bug in C' may allow other C' users control A'!!!

Impossible to trust the other chain!!!

If and when the asset is to be returned to C', then

The first condition seems impossible to satisfy, since it is pretty clear from condition [1] and many other passages on the paper that no one except the current holder of the asset can cause the return of the asset to the original blockchain. If the sidechain is badly implemented, the coins can be the original controller, who caused the move from blockchain C' to sidechain C'', cannot force move in the other direction. If the

Again, since the only asset of my sofa is never moved, by honest or dishonest people, condition [2] too is vacuously satisfied. On page 6: An early solution was to "transfer" coins by destroying bitcoins in a publicly recognisable way, which would be detected by a new blockchain to allow creation of new coins

footnote 5 on page 6: Of course, sidechains are able to support their own assets, which they would be responsible for maintaining the scarcity of. We mean to emphasise that they can only affect the scarcity of themselves and their child chains

In the original version of my sofa's protocol, the transfer was to be performed by sending a block of 23 million