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 Software-based wallet
Digital currency
Software-based wallet
simplied payment verication (SPV)

4. Introduction(2/2) SPV Getheaders Transaction’s hash value Block
Merkle tree needs hash value
Calculates merkle root hash
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。
Compare with block header’s merkle root hash

5. Preliminaries –Blockchain and merkle tree(1/2)
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

6. Preliminaries –Blockchain(2/2)
$10
Book
Amanda
Bob
Decentralization
Immutability 6

7. Proposed scheme – framework of SBLWT

8. 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

9. Proposed scheme – reliable switching
Transaction occurs
Rich OS suspended
Restores secure OS and SBLWT
Non-Maskable Interrupt(NMI)
Private key, address, block header
Footprints in SEE will clean up

10. 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, +, /

11. Proposed scheme – secure sync and verification

12. Proposed scheme – secure sync and verification

13. Security analysis
Secure booting
Information leakage
DOS attack

14. 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

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

16. 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

17. Conclusions
Trustzone
Confidentiality and integrity