This doesn't require any difficult encryption: just split your private key into two uniformly random strings which XOR to the correct value (ie, generate one half randomly, and XOR it with the private key to get the other).This doesn't require any difficult encryption: just split your private key into two uniformly random strings which XOR to the correct value (ie, generate one half randomly, and XOR it with the private key to get the other).

That doesn't work. If you do that, then every time you send money, then to sign an outgoing transaction, you have to put the two keys back together on one or the other of the two computers. The point of using homomorphic encryption is to avoid doing that, since it creates an opportunity to steal the combined key.