1. SBLWT: A Secure Blockchain Lightweight Wallet Based on Trustzone
Source : IEEE Access, Vol. 6, pp , July 2018
Authors : Weiqi Dai, Jun Deng, Qinyuan Wang, Changze Cui, Deqing Zou, and Hai Jin 
Speaker : Fengyu Chiu
Date : 2019/1/3
中國武漢(華中科技大學 )

2. Outline Introduction Preliminaries Proposed scheme Security analysis
Performance analysis
Conclusions

3. Introduction(1/2) Hardware-based wallet Digital currency
Software-based wallet
simplied payment verication (SPV) wallet
Stagefright
MMS(Multimedia Messaging Service)

4. Block header merkle root
Introduction(2/2)
SPV
Transaction
Hash
Detail information
Merkle route
Tx-hash
SPV node
Full node
0.從網絡上獲取並保存最長鏈的所有block header至本地； 1.計算該交易的hash值tx_hash； 2.定位到包含該tx_hash所在的區塊，驗證block header是否包含在已知的最長鏈中； 3.從區塊中獲取構建merkle tree所需的hash值； 4.根據這些hash值計算merkle_root_hash； 5 .若計算結果與block header中的merkle_root_hash相等，則交易真實存在。 6.根據該block header所處的位置，確定該交易已經得到多少個確認。
Merkle root
= ?
Block header merkle root

5. Preliminaries –Blockchain(1/3)
$10
Book
Amanda
Bob
Decentralization
Immutability 5

6. Preliminaries –Blockchain and merkle tree(2/3)
Block header
Block header
Block header
Timestamp
Prev hash
Nonce
Merkle root
Timestamp
Prev hash
Nonce
Merkle root
Prev hash
Nonce
Merkle root
Timestamp
Hash 01
Hash 23
Hash 0
Hash 1
Hash 2
Hash 3
Tx0
Tx1
Tx2
Tx3

7. Preliminaries –Trustzone(3/3)7

8. Proposed scheme – Framework of SBLWT

9. Proposed scheme – Secure booting
Normal Execution Environment
Secure Execution Environment
Normal bootloader
Secure OS boot
Integrity
Normal OS boot
Flash Device bootloader
SBLWT
System running
ROM SOC bootloader
Device power on

10. Proposed scheme – Reliable switching
NMI (Non-Maskable Interrupt)
Secure Execution Environment
Secure OS
SBLWT
Secure storage
Normal Execution Environment
Rich OS
NMI
Non-secure storage
Encrypted
Block headers , private key and address

11. Proposed scheme – Secure keys and reliable addresses
Private key
Secp256k1
Public key
Attackers
Double hash
Address
The hash of Public key
Base58Check
0, O, I, l, +, /

12. Proposed scheme – Secure sync and verification

13. Proposed scheme – Secure sync and verification

14. Security analysis Secure booting Information leakage Secure booting
Integrity
SBLWT
Secure booting
Information leakage
Secure booting
DOS attack
NMI

15. Performance analysis(1/3)
Operations
Times 1
Environment switching
1.7 us 2
read(1KB)
2 ms 3
write(1KB)
12 ms 4
SBLWB check
1.54 ms 5
Information cleanup
0.521 ms
Module
lines 1
prikey generate
543 2
Address generate
309 3
sync
1037 4
verification
559
The detail TCB of SBLWT
Some overheads of SBLWT

16. Performance analysis(2/3)
SHA-256 speed comparision

17. Performance analysis(3/3)
Normal SPV wallet
SBLWT
start
1.387 s
1.443 s
verification
2.283 ms
3.137 ms
SBLWT’s start and verify overhead comparision

18. Conclusions
Trustzone
Confidentiality and integrity