Can the HF-90 hop sequence be “cracked” and then followed and intercepted?
A. In order to crack a code, information on different values in the sequence must be obtained. For a frequency hopping net this means that it is necessary to log a long series of frequencies which have been hopped over. The following issues make this task insurmountable: 1. The HF spectrum is crowded and identifying one specific net is very difficult among all other signals. 2. A hopping net is actually silent a lot of the time resulting in missed sequence values as far as an interceptor is concerned. 3. Due to the fact that SSB is used for voice transmissions, there will be no output between syllables and consequently no sequence value for an interceptor. 4. As there is no carrier with an SSB channel, identifying which frequency is being hopped on is difficult for an interceptor. All of the above make the task of cracking the code much more difficult than on a wire line system.
