For detecting double spending, secret splitting is used. If a user duplicates the coin, then there will be two different transaction items in transaction list. What is the probability of catching a user who duplicates the coin using this technique?
To clarify:
https://www.cs.bham.ac.uk/~mdr/teaching/modules03/security/students/SS4/DigitalCash.pdf shows on slide 13 of 17 that the probability of catching a user is $1-(\frac{1}{2})^n$ where $n$ is the number of identity pairs used in the transaction item. But how do you calculate it?