CC2538: NWK header and NWK aux header encryption

Dhanraj

Guru 14820 points

Part Number: CC2538
Other Parts Discussed in Thread: Z-STACK, TIMAC

Hello,

why there is no provision of encryption of Nwk header and Nwk aux header in zigbee packet??

over 8 years ago

0 YiKai Chen over 8 years ago

Guru 735695 points

What's the point to encrypt those header?

0 Dhanraj over 8 years ago in reply to YiKai Chen

Guru 14820 points

we can see full address of source and destination

the sequence number is visible

the NWK frame counter is visible

don't you think this information increases the possibility of a replay attack

0 YiKai Chen over 8 years ago in reply to Dhanraj

Guru 735695 points

Even you can see those but how can you do replay attact without network key? By the way, if you have better proposal, I suggest you to propose to Zigbee Alliance.

0 Dhanraj over 8 years ago in reply to YiKai Chen

Guru 14820 points

I dont have any proposal,
i just started sniffing data without saving any key in sniffer , and tried to understand , what data we can see without having key and how it can be helpfull to attacker.

In network aux header, why it is showing "Network security level :[0x0] None " what does this mean ??

0 Ryan Brown1 over 8 years ago in reply to Dhanraj

TI__Guru**** 222717 points

Please read Section 4.3 (NWK Layer Security) of the Zigbee_Pro Specification. This security level sub-field is obtained from the nwkSecurityLevel attribute from the NIB, you can control this with the NLME_SetRequest API.

Regards,
Ryan

0 Abhay Joshi over 8 years ago in reply to Dhanraj

Intellectual 810 points

The Network Security Level is set to 5 which corresponds to a 32 - bit MIC. As per the Zigbee Specification, the Security Level is cleared after encryption of the payload and transmitted over the air. While decrypting the packet, the Security Level is set to 5 (in the decryption nonce as well).

0 Dhanraj over 8 years ago in reply to Abhay Joshi

Guru 14820 points

what level value should I set to encrypt NWK header as well as NWK aux header?

0 Abhay Joshi over 8 years ago in reply to Dhanraj

Intellectual 810 points

The Encryption Level corresponds to Network Payload encryption. Network Header and Network Aux Header are not encrypted. If you wish to encrypt the Network Header and the Network Aux Header, you would need to enable MAC Security as they are part of MAC Payload.

Zigbee, by itself, doesn't define the MAC Level encryption - decryption. Interoperability would go for a toss unless the MAC at other end has security enabled.

0 Dhanraj over 8 years ago in reply to Abhay Joshi

Guru 14820 points

How can we implement MAC level encryption -decryption in z-stack

0 YiKai Chen over 8 years ago in reply to Dhanraj

Guru 735695 points

You cannot do this since MAC layer is not available for application developer.

0 Dhanraj over 8 years ago in reply to YiKai Chen

Guru 14820 points

If we get full source code of z-stack , then is it possible to Add mac layer security?

0 YiKai Chen over 8 years ago in reply to Dhanraj

Guru 735695 points

If you get full source code, I suppose you can do whatever you want.

0 Dhanraj over 8 years ago in reply to YiKai Chen

Guru 14820 points

1) does anyone tried adding mac layer encryption before?

2) As per current discussion NWK aux header is not encrypted.

But In my other post JasonB had mentioned that "NWK frame counter value is encrypted"

the NWK frame counter is part of NWK aux header then how can it be encrypted?

0 Abhay Joshi over 8 years ago in reply to Dhanraj

Intellectual 810 points

To answer your questions,

1) If you use TIMAC and build your own stack on top of it, you can control the MAC however you want to. As YK Chen mentioned before, in Z-Stack, the MAC is not exposed to the user and security is not enabled for MAC as Zigbee defines only Network Layer and APS Layer security. It doesn't insist on MAC Layer security which is defined by IEEE 802.15.4.

2) I am particularly not aware of the encryption of the Network Frame Counter. Typically, the Network Header and Network Aux Header are not encrypted. You can refer to the Zigbee R21 Specification (Securing Packet At Network Layer) and check the Auxiliary Header Frame Format.

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CC2538: NWK header and NWK aux header encryption