The security that is used in e-cash is cryptographic algorithms where is a key to create a tamper proof e-cash which can be traces back to where it is being issued. The usage of the e-cash is anonymous which means the e-cash could not be traced back to find out who sent it.
Each of the e-cash is embedded with a serial number and the number will not be used again. E-cash also has threat prosecution where it’s the main security in order to prevent double spending. This is made possible due to the complicated two-part lock which provides the e-cash with anonymous security and informs when someone is attempting to double the spent cash.
Reference:
http://homepages.inf.ed.ac.uk/dts/pm/practical/ecash.htm
https://www.bs-card-service.com/en/card-acceptance/debitkarten/electronic-cash-debitkarte.html
