LWM2M Security 0 urn:oma:lwm2m:oma:0 Multiple Mandatory LWM2M Server URI Single Mandatory String 0-255 bytes Bootstrap-Server Single Mandatory Boolean Security Mode Single Mandatory Integer 0-4 Public Key or Identity Single Mandatory Opaque Server Public Key Single Mandatory Opaque Secret Key Single Mandatory Opaque SMS Security Mode Single Optional Integer 0-255 SMS Binding Key Parameters Single Optional Opaque 6 bytes SMS Binding Secret Key(s) Single Optional Opaque 16-32-48 bytes LwM2M Server SMS Number Single Optional String Short Server ID Single Optional Integer 1-65534 Client Hold Off Time Single Optional Integer s Bootstrap-Server Account Timeout Single Optional Integer s