Abstract: An electronic payment device and its method using an unbalanced binary tree are disclosed. The total unit n of the amount of money that user purchases is decomposed first into a Matrix of p rows×q columns. Then, a first one-way function h1 and a second one-way function h2 serve to define the one-way function operation of the first row and each column, respectively. When two numbers of operation times a and b are calculated by their formulas respectively, they are substituted into formula Xk=h2b(h1a(Xpq)). Namely, by the first one-way function h1, a times of operation is performed, and then by the second one-way function h2, b times of operation is performed, thus, a first data Xk of current consumption can be derived rapidly. The present invention has only a few times of operation, thus the calculating efficiency is improved greatly.

Abstract: A simply structured bi-functional roller skate has a pair of shoe embodiments. Each shoe embodiment is provided with a front securing seat which is a tubular device with a forwardly extended board, and a rear securing seat which is a tubular device with a backwardly extended board. Both the front and rear securing seats are embedded at the front end and the rear end of each shoe embodiment respectively. Each tubular device of the front and rear securing seats is in alignment with an engagement hole so as to permit a first and a second wheel axle each having a proper length to be led therethrough at the front and rear end of a shoe embodiment. Each wheel axle has a knob-ended locking screw at one end and an internally threaded section at the other end so as to permit the knob ended locking screw to be secured to the end of each wheel axle after roller wheels are mounted to the wheel axles respectively.

Abstract: A simply structured bi-functional roller skate has a pair of shoe embodiments. Each shoe embodiment is provided with a front securing seat which is a tubular device with a forwardly extended board, a rear securing seat which is a tubular device with a backwardly extended board. Both the front and rear securing seats are embedded at the front end and the rear end of each shoe embodiment respectively. Each tubular device of the front and rear securing seats is in alignment with an engagement hole so as to permit a first and a second wheel axle each having a proper length to be led therethrough at the front and rear end of a shoe embodiment. Each wheel axle has a knob-ended locking screw at one end and an internally threaded section at the other end so as to permit the knob ended locking screw to be secured to the end of each wheel axle after roller wheels are mounted to the wheel axles respectively.