A Simple Off-line E-Cash System with Observers

  • Eligijus Sakalauskas Kauno Technologijos Universitetas
  • Inga Timofejeva Kauno Technologijos Universitetas
  • Aleksėjus Michalkovič Kauno Technologijos Universitetas
  • Jonas Muleravičius Kauno Technologijos Universitetas
Keywords: e-cash, e-wallet, observers, physical unclonable function (PUF).


A simple and transparent mobile e-cash system with observers is presented. Observers are cryptographic bank chips inserted in customer’s payment device, e.g. smart phone. System satisfies e-cash divisibility, anonymity, off-line payments, transferability and double-spending prevention requirements. Proposed e-cash system is based on two well-known cryptographic primitives, namely ElGamal encryption and Schnorr identification protocols, therefore it can be named as simple and transparent in the sense of security considerations. In Schnorr identification scheme Brand’s double spending prevention protocol is implemented during payment protocol. The use of observers allows to avoid e-cash data growing in size as it takes place in all divisible, anonymous, off-line and transferable e-cash systems. To increase observer’s security and avoid their clonability the use of physical unclonable function in the chip of observer is proposed.

DOI: http://dx.doi.org/10.5755/j01.itc.47.1.18021

Author Biographies

Eligijus Sakalauskas, Kauno Technologijos Universitetas
Profesorius taikomosios matematikos katedroje.
Inga Timofejeva, Kauno Technologijos Universitetas
KTU taikomosios matematikos bakalaurantė
Aleksėjus Michalkovič, Kauno Technologijos Universitetas
Lėktorius taikomosios matematikos katedroje.
Jonas Muleravičius, Kauno Technologijos Universitetas
KTU informatikos (09P) doktorantas