devAddr = the address of the device you can register a block at http://thethingsnetwork.org/wiki/AddressSpace
appSkey and nwkSkey are used for encryption and integrety - for the TTN network they are set to {0x2B, 0x7E, 0x15, 0x16, 0x28, 0xAE, 0xD2, 0xA6, 0xAB, 0xF7, 0x15, 0x88, 0x09, 0xCF, 0x4F, 0x3C};