[1] Univ Illinois, Dept Comp Sci, Chicago, IL 60607 USA
[2] Tech Univ Eindhoven, Dept Math & Comp Sci, NL-5600 MB Eindhoven, Netherlands
[3] Univ Waterloo, Inst Quantum Comp, Waterloo, ON N2L 3G1, Canada
[4] Ruhr Univ Bochum, Horst Gortz Inst IT Secur, Bochum, Germany