Authenticated Validity for M2M devices
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number:
IEEE S802.16p-11/0251r1
Date Submitted:
2011-09-09
Source:
Eldad Zeira
InterDigital
Voice:
E-mail: eldad.zeira@interdigital.com
Venue:
IEEE 802.16n at session #75
Base Contribution:
C802.16p-11/0251
Purpose:
To be discussed and adopted by 802.16p
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1
Authenticated Validity for M2M devices
IEEE S802.16p-11/0251r1
M2M networks are vulnerable
• M2M networks are more vulnerable to security threats
due to longevity and field updates / provisioning
• M2M networks are required to handle critical missions
without human intervention
• Attacks can lead to false situational awareness, loss of
privacy, DOS
• In some cases network attacks = physical attacks
• EAP doesn’t protect from tampering
IEEE S802.16p-11/0251r1
M2M Vulnerabilities
IEEE S802.16p-11/0251r1
802.16p Requirements: SRD
6.4 Security Support
The 802.16p system shall support integrity and
authentication of M2M devices, as well as integrity and
privacy of M2M application traffic which requires a
secure connection.
6.4.1 The 802.16p system shall support a device validity
check between the device and the network.
6.4.2 The 802.16p system shall enable a flexible security
suite that can be adjusted per the security requirements
of the M2M application
IEEE S802.16p-11/0251r1
We need to:
• Prevents a potentially tampered device from
accessing services (e.g. multicast) and performing
DOS attacks
• Provides the network with evidence of tampering
– So owner can take action
• Imposes minimal burden on devices that do not
require integrity validation: optionality of
integrity validation
– Must be able to mix different device types in single
network
IEEE S802.16p-11/0251r1
The basis:
• Devices which need integrity validation have an
(unspecified) difficult to tamper with module
which can test the validity of the device as a
whole.
• Failed devices must not attempt to connect… but
that in itself does not provide the network with
any validity proof
IEEE S802.16p-11/0251r1
What are our alternatives?
A. Prevent release of EAP certificate if test failed
B. Prevent release of EAP certificate if test failed +
add information regarding this capability of the
device
Both require that EAP is made mandatory and used
for key derivation
C. Send certificate confirming the passing of the
validity test after keys are established
1. In RNG-REQ
2. “higher layer” messages
IEEE S802.16p-11/0251r1
Network behavior:
Network behavior for Alt-A:
Device type
Not applicable
EAP certificate sent
Authorize device
EAP certificate NOT sent
Do not authorize device
Network behavior for Alt-B:
Device type
Validity test capability
indicated
Validity test capability NOT
indicated
EAP certificate sent
Authorize device
N/A
EAP certificate NOT sent
Do not authorize device
alert for rogue device
Do not authorize device
Network behavior for Alt-C:
Device type
Validity test capability
indicated
Validity test capability NOT
indicated
validity certificate sent
Authorize device for sensitive
information
N/A
validity certificate NOT sent
Expire keys
alert for rogue device
Do not authorize device
for sensitive
information, BUT
allow other services
No difference between C-1 & C-2, as long as validity information is timely and there is a mechanism for retries if message fails.
These already exist for RNG-REQ/RSP
IEEE S802.16p-11/0251r1
Conclusions:
• If EAP is used for the validity test then EAP must be mandatory
• Use of EAP does not allow to mix devices which have validity
testing and those which have not.
– A device that doesn’t have validity test implemented will be able to present
itself as valid and have access to all sensitive information.
• Sending a separate certificate (in addition to EAP or RSA) plus
information regarding device type:
– Allows to differentiate between devices with and without validity testing
and offer different services to each in the same deployment
– Doesn’t make EAP mandatory
– Provides confidentiality to device type
IEEE S802.16p-11/0251r1
Elements of tamper detection & mitigation
• A Trusted Element (TE) tests for tampering
– TE is NOT mandatory for all devices; Capability & implementation are out of
scope
– TE, if implemented, should be tamper resistant
• A device that fails the test does not attempt to access network
• Send Device Validity Information to network: within time limit,
confidentially and with integrity protection,
– Validity testing capability information (e.g. as H/W, S/W certificates)
– Validation certificate (if implemented)
- The only requirement mandatory to all devices in the network;
-Needed to prevent tampered devices from pretending it doesn’t
have the capability
-Provides tampering evidence to network
IEEE S802.16p-11/0251r1
The network MAY, if device validity check IS:
Successful,
• Establish additional keys
that may be used for
additional services
– Multicast access
– Sensitive user payload
Unsuccessful,
• Cause key(s) to expire
• Send an (unspecified)
command that affects device
behavior (e.g. re-boot, “safe
mode”, etc.)
IEEE S802.16p-11/0251r1
MS behavior for device integrity validation
Validity
Self Test
Passed?
Y
Un-touched
Boot - Up
- Synchronization
- Capability Exchange, network
parameters
- Authorization & Key exchange
Validity information sent to
network with registration
N
Network examines validity
information
Safe mode behavior
N
Validity accepted?
Keys expired
Retries possible
Y
Normal Op
(new keys may be
exchanged)
IEEE S802.16p-11/0251r1
The procedure (1/2)
1. AMS that has a TE and failed the validity test shall not attempt to
enter the network.
1.
Provides protection from DOS attacks on AAA server; nature of protection
depends on implementation.
2. The AMS sends its validity testing capability information (e.g. as
H/W & S/W build certificates) and optionally its validation
(integrity) certificate in AAI-REG-REQ.
1.
2.
3.
Shifts integrity responsibility to network
Provides network with tampering attempt information
Part of the network access state machine
3. Out of scope for 802.16p:
1.
2.
3.
ABS forwards the received information to the network.
If device validity is not acceptable, the network may expire keys.
Otherwise the network or AMS may initiate new services and new keys
IEEE S802.16p-11/0251r1
The procedure (2/2)
4. The ABS response in AAI-REG-RSP indicates whether
the device validity has been accepted or not.
4. Prevents need to wait until next transmission to find out keys
have been expired
5. AAI-REG-RSP with negative confirmation shall be
interpreted as an abort. The AMS behavior in this case
is FFS.