97 Blob := committing to 0 or 1, without revealing the value committed to 1)The user committing the value must not be able to change it, but he must be able to reveal it.
{"Image DocumentName": "Blob := committing to 0 or 1, without revealing the value committed to", "Image ImageDescription": "The user committing the value must not be able to change it, but he must be able to reveal it. 1? s Z p randomly chosen. (so user cannot compute e such that s \uf0ba \uf061e) x := sb mod p with 0 \u2264 y \u2264 p-2. commit. open. The others should not get any information about the value. 2? Let 2u be the smallest number that does not divide p -1. y := y1, b, y2 with 0 \u2264 y \u2264 p-2 and |y2| = u -1. x := mod p. commit. open. In a digital world you can get exactly one property without assumptions, the other then requires a complexity-theoretic assumption. Example: Given a prime number p and the prime factors of p -1, as well as a generator of Z p (multiplicative group mod p). Using y everybody can calculate mod p. The inverse can not be done efficiently! physical implementation: write on blackboard. 1? \uf0e0 info theor secure no integrity. Vertraulichkeit: a \uf0e0 Generator \uf0e0 s^b = a^x^b a^y=a^(x b) a^y=a^(x b+y) Integrit\u00e4t: gegeben: a^(x b+y); b \uf0e0 gesucht y \uf0e0 x muss berechnet werden. 2? integrity ok, no info theo secure. no confidentiality: claculate y! integrity: y_2 \uf0e0 constant ; y\uf0e0 fest \uf0e0 b fest. x. x. y. y.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}