I think you may be misuderstanding the Public Key advice.

I wish I could claim credit for the PKE idea (illustrated below), but he understood what I meant correctly. The advice I gave was based on the fact that the OP only said that the laptops used the data. Since I wrote that post, he has changed the requirements such that the laptops now collect the data.

 work db             secret db
 (laptop)            (under lock and key)
+------------+       +-------------+
| public key |       | private key |
+------------+       +-------------+

+-----------+---
| public id | ...
+-----------+---
| public id | ...
+-----------+---
| .
| .
| .
[download]

The public id would be the real id encrypted using the public key.