<P> The P - code is also a PRN; however, each satellite's P - code PRN code is 6.1871 × 10 bits long (6,187,100,000,000 bits, ~ 720.213 gigabytes) and only repeats once a week (it is transmitted at 10.23 Mbit / s). The extreme length of the P - code increases its correlation gain and eliminates any range ambiguity within the Solar System . However, the code is so long and complex it was believed that a receiver could not directly acquire and synchronize with this signal alone . It was expected that the receiver would first lock onto the relatively simple C / A code and then, after obtaining the current time and approximate position, synchronize with the P - code . </P> <P> Whereas the C / A PRNs are unique for each satellite, the P - code PRN is actually a small segment of a master P - code approximately 2.35 × 10 bits in length (235,000,000,000,000 bits, ~ 26.716 terabytes) and each satellite repeatedly transmits its assigned segment of the master code . </P> <P> To prevent unauthorized users from using or potentially interfering with the military signal through spoofing, it was decided to encrypt the P - code . To that end the P - code was modulated with the W - code, a special encryption sequence, to generate the Y - code . The Y - code is what the satellites have been transmitting since the anti-spoofing module was set to the "on" state . The encrypted signal is referred to as the P (Y) - code . </P> <P> The details of the W - code are kept secret, but it is known that it is applied to the P - code at approximately 500 kHz, which is a slower rate than that of the P - code itself by a factor of approximately 20 . This has allowed companies to develop semi-codeless approaches for tracking the P (Y) signal, without knowledge of the W - code itself . </P>

The encrypted version of the p code is the