64 bit arithmetic soft fork

[ProofOfKeags]

@sipa

One possibility is having an OP_ENABLE64BIT, which has no effect on the stack when executed, but its presence in a script makes all arithmetic opcodes accept up to 8-byte inputs for example

I’m generally skeptical of increasing the surface area of the state variable of the script VM. I’ll admit I don’t know script backwards and forwards but all of my experience with it so far points me to the fact that the only thing opcodes operate over is the main and alt stacks as well as halting execution of the VM. As such it seems that the existing VM can be modeled by a state transition function:

exec_op : (MainStack, AltStack) -> (MainStack, AltStack)

Doing something like OP_ENABLE64BIT would introduce some third VMInterpreterState and I think that will dramatically increase the surface area of potential consensus issues. Correct me if I’m wrong but this would be a fundamentally new structural change to the VM formalism.