From the beginning of amateur radio, enthusiasts have exchanged written confirmation of contact in the form of QSL cards. These cards are sent through the mail. Since most amateur radio enthusiasts are also interested in technology, there was a need to find a way to automate this system. Amateur radio operators can now use the electronic version of proving that contact was established, which is known at the LoTW (Logbook of The World) program. While some amateur radio hobbyists continue to use paper QSL cards, many are switching to the electronic version.
An obvious choice was to use digital signature technology (not to be confused with online signatures) and the Internet. Most hams already log their radio contacts on computers and have Internet connectivity. Just like with signatures which used to be pen and paper, QSL cards are becoming electronic. Both electronic signatures and QSL cards use Public Key Infrastructure technology to authenticate the signer/contact. Both a traditional QSL card, and electronic record of contact can be used to earn a credit or prize, so it is important that the identity of the contact can be validated.
Just like with pen and paper signatures, QSL systems required more resources than their new electronic counterparts. Before, amateur radio enthusiasts would send two dollars, along with a prepaid envelope for the other person to send their QSL card. Since most amateur radio operators make thousands of contacts, especially during contests, this quickly becomes expensive. It also takes a long time to receive the QSL card through the mail. The paper QSL system is also less secure than the electronic version, as a QSL card can be submitted even if it contains mistakes, or is invalid.
The ARRL (American Radio Relay League) developed their own Certificate Authority code so they could function as the certificate issuer for the public key infrastructure, since buying the software would have been too costly. The new electronic system to establish contact (LoTW) works the following way:
1) The applicant obtains a Callsign certificate specified by the Station Location.
2) Uses the callsign specified in the Callsign Certificate to select the private key.
3) Uses the private key to encrypt the QSO (contact), placing both the Callsign Certificate and the encrypted information in a digitally signed Log file.
4) Sends the digitally signed Log file to the LoTW Server. The LoTW Server uses the public key in the Callsign Certificate to decrypt the QSOs in the Digitally Signed Log file, thereby authenticating the user as the source of these QSOs.
5) The Logbook Server verifies the signature on the log and sends the log information to the Logbook of the World Database.
7) When a contact is confirmed by both parties it is added to the Confirmed Contacts Database.
To learn more about the use of Public Key Infrastructure and amateur radio, or the Logbook of The World, visit the Amateur Radio Relay League at http://www.arrl.org/logbook-of-the-world