| 主权项 |
1. A method to perform a “reader challenge setup step in an authentication phase”, according to MIFARE contact-less technology authentication and encryption protocol, in a “tag device”, wherein, a size of an internal state of a cipher, called “ST” is 6 bytes, at time t, the internal state of the cipher is represented by STt=(STt[0], . . . , STt[5]), a reader challenge, called “RC “, of length 4 bytes, is denoted by: RC=(RC[0], RC[3]) a linear function “LF” performing a linear feedback function of a MIFARE contact-less technology linear feedback shift register, and a non linear function, “NLF”, performing a MIFARE contact-less technology two-layer filter generator, are used to update a value of said ST using the RC,wherein the method comprises at least the following steps:
storing, in a memory of said tag device, four tables f1i, f1p, f2i, f2p; from an initial state of the reader challenge setup step denoted by STto', computing by a processor of said tag device, the successive states STt0+8, STt0+16, STt0+24, STt0+32 by computing byte per byte a linear feedback value using the function LF; and injecting, by said tag device, byte per byte the “RC” into the ST using said four tables f1i, f1p, f2i, f2p and the function NLF. |
