| 摘要 |
A rolling code, used to operate barriers and the like, is encrypted by, in the embodiment described, mirroring all or a subset of the bits of the code. A section of the encrypted code is then selected and used to address a lookup table which stores data bit order patterns and data inversion patterns (figs. 9 and 10). A transmitted code comprises a portion made up of e.g. sync data and a portion made up of fixed and rolling code data (fig.8). The fixed data and rolling code data are divided into groups (fig.7). The data bit order patterns are used to select one bit each from the groups specified in the bit order pattern, for transmission e.g. as a triplet. Ternary to binary conversion may be used. The bit inversion patterns specify which, if any, of the selected bits are to be inverted prior to transmission. Multiple groups (e.g. 10 in fig.8) are transmitted in this way. The sections of the encrypted code used to address the lookup table are included in the part of the transmitted message bearing sync data, for use at the receiver. |
