No they can't "hack" the system - they can try do a double-spend, but it would be very expensive. The cost is proportional to chain length. What's the cost of

No they can't "hack" the system - they can try do a double-spend, but it would be very expensive. The cost is proportional to chain length. What's the cost of creating a parallel chain in "Oroborus" as a function of chain length?