for Constrained IoT Devices Y. Jia, B. Liu, W. Jiang, B. Wu, C. Wang - - PowerPoint PPT Presentation

HUAWEI TECHNOLOGIES CO., LTD.

Enhancing Remote Healthiness Attestation for Constrained IoT Devices

• Y. Jia, B. Liu, W. Jiang, B. Wu, C. Wang

IEEE ICNP 2020 Madrid, Spain, October 13-16, 2020

IoT Devices are keeping losing control…

IoT devices remain vulnerable… Hackers are lunching DDoS with IoT devices…

Mirai attacks…

Peak 1.7 Tbps

IoT Devices

Reasons behind the constantly vulnerabilities

Constrained Resources… Market Shaping Hacking Hacker Unaffordable Security mechanisms IoT Hacked!

Given that IoT devices are inevitably vulnerable, the question goes to:

How could we timely identify hacked IoT devices? Remote Attestation

Universal Remote Attestation

Started Power off

BOOTUP Trusted boot mechanism

Credentials

Endorsed by Trusted Module

STEP 1 STEP 2

Trusted Module Running IP Network Channel

• Built by the manufacturer
• Trusted by the Authorized Verifier
• All in an out-of-band manner

Pull the Credentials With the Trusted Module endorsement Trusted Boot Remote attestation

A dedicated Trust Module is way too heavy/expensive…

Could it be evolved for the constrained IoTs? DICE(Device Identifier Composition Engine)

The DICE(Device Identifier Composition Engine) Proposal

• Initially proposed by Microsoft
• Standardized by
• standardize 2 specifications of the DICE-based remote attestation

symmetric crypto DICE asymmetric crypto DICE

① ②

Standardized by 2020 Standardized by 2018

DICE with the Asymmetric crypto

Device Side Verifier Side

DICE Engine [SK*] Layer 0

[SK0]

Layer 1

[SK1]

Layer 2

[SK2]

Layer n

[SKn]

… …

Signed by SK* Certificate 0

PK0

Signed by SK0 Certificate 1

PK1

Signed by SK1 Certificate 2

PK2

Signed by SKn-1 Certificate n

PKn … … Hash(L0) Hash(L1) Hash(L2) Hash(Ln)

Signed by SK* Certificate 0

PK0

Signed by SK0 Certificate 1

PK1

Signed by SK1 Certificate 2

PK2

Signed by SKn-1 Certificate n

PKn … … Hash(L0) Hash(L1) Hash(L2) Hash(Ln)

Signed by SKCA Certificate IDevID

PK* DTLS Handshake [Authentication]

Database H0 | H1 | H2 | H3 | … | Hn BOOTUP Signed by SKCA Certificate ROOT

PKCA Prerequisites

• DICE Engine is developed and installed by the manufacturer;
• The source code of the DICE Engine too tiny to be hacked;
• DICE Engine is unconditionally trusted by the Verifier;

The higher the layer is, the more functions and attacking surface there will be.

Bootup layer by layer

Design Key:

• DICE Engine stores a SK(private key)/PK(public key) pair for the endorsement;
• DICE Engine will be shut down immediately once layer 0 booted up;
• The short running interval guarantees that the SK(private key) is only readable

for the DICE Engine itself, and thus inaccessible by any other layers;

The validation is based on the certificate-chain

DICE with the Symmetric crypto

ID PSK* DICE UDS*

… …

Secret0=HMAC(UDS, H(L0))

Layer 0 Secret 0

Secret1=HMAC(Secret0, H(L1))

PSK=KDF(Secretn) Layer 1 Secret 1 Layer 2 Secret 2 Layer n Secret n Layer n-1 Secret n-1

Secret2=HMAC(Secret1, H(L2)) Secret3=HMAC(Secret2, H(L3)) Secretn=HMAC(Secretn-1, H(Ln))

Database H0 | H1 | H2 | H3 | … | Hn Database UDS DTLS Handshake [Authentication]

BOOTUP

ID Firmware Version PSK

Device Side Verifier Side

Key Points

• UDS: Unique Device Secret --- A Symmetric key
• The UDS is shared with and trusted by verifiers

The validation is based on the Hash-chain

The design principles are all the same as the Asymmetric crypto based DICE

The Algorithm is the same as the device boot up

Algorithm

Firmware Version

Consistency Validation

NEVERTHELESS Replay Attacks are behind DICE…

Credentials H323CD87LKUE7BGH…

Unconstrained IoT Devices（Powered） Constrained IoT Devices（Battery）

e.g. TEE Credentials 7LK5UE27B5GHFEG3Y… Steal the credential By access devices physical or remotely

NOTE：DICE DO NOT offer the capability of the secure storage

Impractical Possible Hardware Level Protection Software Level Protection

Threat: steal the credentials and then replay…

Replay…

The credential is static… Once stolen the replay attacks survives…

DICE+: Design Consideration

Direction 1：Replay attack resilience Direction 2：adaptive for the constrained IoT Devices Direction 3：Fine-grained firmware attestation

Secure Light-weight Accuracy

DICE

DICE+

UPGRADE…

Main Consideration

Identifying the replay...

Static Dynamic Convert the Credential from STATIC to DYNAMIC !

SEED Nonce Counter Timestamp

DICE+: Design Details Evolution from the Symmetric crypto DICE

UDS

KEY0

… …

KEY0=HMAC(UDS, CNT) Secret0=HMAC(LUDS, H(L0))

Secret0 Layer 1 KEY1

KEY1=H(KEY0)

Secret1

Secret1=HMAC(KEY0, H(L1))

KEYn

Secretn=HMAC(KEYn-1*, H(Ln))

Secretn

BOOT

… …

PSK=H(D)

KEYn=H(KEYn-1)

CNT+1 Every time bootup

D = (Secret0, Secret1, Secret2, … , Secretn)

CNT

DTLS Handshake [Authentication]

Device Side Verifier Side

Algorithm

PSK* Database H0 | H1 | H2 | H3 | … | Hn Database UDS ID Firmware Version PSK

The Algorithm is the same as the device boot up

DICE Layer 0

D* D ID Firmware Version

Consistency Validation

• Seed involved: A counter is introduced in the DICE engine

Layer n KEYn

CNT

MAIN CHANGES

• Symmetric crypto: remain the extreme light-weight overhead
• New algorithm: A parameter is introduced in every layer boot up

OTHER OPTIMIZATIONS

CHALLENGE 2：Computationally costly

• Asymmetric crypto computation consumes energy
• Certificate-chain transfer consumes energy

CHALLENGE 1：Replay Attack

• The static credentials are easy to replay…

CHALLENGE 3：Coarse-grained attestation

• Verifiers are unable to identify the specific hacked layer

UPDATE 2：Extreme constrained IoT

• 1. energy consumptions reduce 1000x
• 2. chip size for security area can reduce ~60%

UPDATE 3：Hacked Layer Identification

• Verifiers are able to identify in which layer the IoT devices

have been hacked.

UPDATE 1：Resilient for Replay

• Verifiers can adjust the period of the validity of the seed
• Verifiers is able to identify the hacked devices that have

been imitated by the replay attacks. DICE [Asymmetric]

DICE+

Conclusion: What DICE+ Improve?

DICE [Symmetric]

HUAWEI TECHNOLOGIES CO., LTD.

THANKS!

IEEE ICNP 2020 Madrid, Spain, October 13-16, 2020