| 摘要 |
In a cellular communication system (eg. TETRA), a receiver can continue to decrypt signals despite checksum errors arising from synchronisation verification failures on behalf of transmitters which do not use real time clocks to calculate the checksum. Synchronisation verification values are transmitted via half-slot stealing and verified according to a local time base, and a fall back mode is entered if the verification value is invalid which allows continued communication, perhaps with a warning that it may comprise a replay attack. Synchronisation may proceed on the basis of previously received parameters (eg a flywheel process). This method allows flexible interoperability in mixed groups of transceivers, some of which incorporate real time clocks and some of which don't. Such failures or errors would usually terminate the communication to protect against replay attacks. |
