LIP-PA: A Logistics Information Privacy Protection Scheme with Position and Attribute-Based Access Control on Mobile Devices

Algorithm 4

Improved position-based key exchange.

1: Landmarks executes:

2: pick keys ,,,,

3: broadcast ,,,, over their private channel.

4: At time , picks large string , computes , and broadcasts

5: At time , picks large string ,, computes , , and broadcasts ,,,

6: At time , picks large string , computes , and broadcasts

7: At time , picks large string , computes , and broadcasts

8: Courier executes:

9: At time , the courier receives all of the strings

10: for    do

11: compute

12: end for

13: return exchange key