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EVM-900-DT

HumDT™ Series RF Transceiver Module

Unspecified 

Encryption

The module implements AES encryption in ECB mode. The packet header

information is sent in the clear and the payload data is encrypted.

Encryption algorithms are complex mathematical equations that use a

number, called a key, to encrypt data before transmission. This is done

so that unauthorized persons who may intercept the transmission cannot

access the data. In order to decrypt the transmission, the receiver must

use the same key that was used to encrypt it. The receiver performs the

same calculations as the encoder and, if the key is the same, recovers the

data.

The AES encryption algorithm is widely used, from basic wireless data links

to Internet traffic to government communications. It is considered highly

secure and reliable. The AES algorithm supports key lengths of 128, 192

and 256 bits. The HumDTTM module only supports 128 bits. The larger key

lengths are more subject to government import and export regulations,

though the user will need to confirm that 128 bits is allowable in their

industry.

The strength of the encryption algorithm and the length of the key are only

two factors in a secure system. The ultimate requirement is the secrecy

of the key. The HumDTTM module only allows the key to be read out of

the Access Point. It can be written into an End Device, but is otherwise

inaccessible.

The AP should be kept in a secure location to prevent physical access by

unauthorized persons. If the key is stored outside the system, such as in a

database or list, then it should also be kept secure.

Restore Factory Defaults

The transceiver is reset to factory default with a serial command

through the Command Data Interface. This command restores all of the

configurations to factory default settings. These are shown in Figure 19.

Factory Default Configurations

Parameter

Default Value

Device Type

ED

Module Address

0x00-0x00-0x00-0x00

Serial Baud Rate

9.6kbps

Channel Mapping

Single Channel (911.5MHz)

TX Output Power

0dBm

Network ID

0x00-0x00-0x00-0x00

All GPIOs

Digital Input with Pull-up

AES Key

0x2B, 0x7E, 0x15, 0x16, 0x28, 0xAE, 0xD2, 0xA6,

0xAB, 0xF7, 0x15, 0x88, 0x09, 0xCF, 0x4F, 0x3C

Figure 19: HumDTTM Factory Default Configurations

The module address is not changed to the factory default. This value is

retained. This serial command requires knowing the current serial baud

rate. If that is not known then all 10 supported rates should be tried to find

out which is correct.

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