| 摘要 |
<p>Device and method for calculating distance in a communication network (100) using Time-To-Live (TTL) values. Device A sets (202) a non-predictable initial TTL value (TTL_S) and sends a message (204) with this TTL value to device B. The TLL value should be at least as high as the TTL ceiling and lower or equal to the maximum TTL value (normally 255). Device B reads (206) the TTL value (TTL_R) of the received message. Device A and device B establish (208, 210) a Secure Authenticated Channel (SAC) (212) over which device B sends (214) the TTL value of the received message (TTL_R). Device A may then calculate (216) the distance to device B. If TTL_R > TTL_S, this indicates an error or an attack; if TTL_R < TTL_S-TTL_C, then device B is too distant; and if TTL_S - TTL_C ‰ TTL_R ‰ TTL_S, then device A may conclude that device B a priori is within the required distance.</p> |
