SWRA615A June 2019 CC1352P , CC1352R , CC2530 , CC2531 , CC2538 , CC2652P , CC2652R , CC2652R7 , CC2652RB , CC2652RSIP
By default, the initial network key is transported to joining devices using the well-known TC Link Key. However, there is now an option of using pre-configured keys and install codes to enhance security even further. Install codes are 128 bits of random data and a 16 bit CRC which are passed through an MMO hash function to generate a TC Link Key. This derived key would be used instead of the well-known TC Link key such that no well-known key is ever used to encrypt data over-the-air. Generally, install code-derived TC link keys are hard-coded into joining devices during the manufacturing process. The corresponding install code is then included with the device and programmed into the network leader through an out-of-band method such as a user interface. High Security mode from R20 has been removed from the R21 specification due to the TC Link Key update and install code enhancements.