Semtech LR1121 - Crypto Engine Use with Lorawan V1.1.X; Figure 11-1: Key Derivation Scheme for Lorawan 1.1.X

LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
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11.3 Crypto Engine Use With LoRaWAN V1.1.x
Figure 11-1: Key Derivation Scheme For LoRaWAN 1.1.x
All the keys required to sign, authenticate, or encrypt Join traffic, as well as the session keys, can be derived from the
provided root keys (AppKey, NwkKey), following the derivation scheme described in Figure 11-1. The arguments of the
CryptoDeriveKey(...) function should be computed by the host controller, and supplied to the function as its
Input[1:16] argument, with appropriate padding bytes when applicable. For instance, when computing FNwkSIntKey, the
command should be used as follows:
FNwkSIntKey = CryptoDeriveKey(NwkKey, 0x01 | JoinNonce | NetID | DevNonce | pad
16
)
Where pad
16
is the required number of 0x00 bytes to expand to a 16-byte number.