Understanding Satellite Navigation

4.4. Encryption

In the last section, we learned that multiplying the data by the code protects the signal from unauthentic users. But that is not enough. Some navigation services require the corresponding signals to be foolproof from any possible unauthenticated use. Hence, encryption is required.

Although encryption is typically applied to the baseband data bits in communications, we will learn about it at this point because in satellite navigation, encryption is generally done at this level on the encoded data bits and not on the bare navigation message data.

However, before we understand the encryption process, we need to know at which level the encryption is really required. In fact, what matters most is what you want to protect. Is it the data ...