【Outline】 We will welcome two blockchain engineers to dive deep into the development of wallets. Yoshikazu Nishimura is a creator of Tachyon wallet that supports Ethereum and all the ERC20 standard tokens. http://tachyon-wallet.io/en/ Alex Melville is an engineer at BitGo. BitGo is a company based in Palo Alto, CA. They make variety of products such as a wallet, an offline vault and institutional custody. https://www.bitgo.com/ It's organized by ICOVO AG. https://icovo.co/

1. Ethereum Hack Tokyo
- Mobile Wallet -
ICOVO AG CTO
Y. Nishimura 2018.05.11

2. Agenda
General Knowledge
1. What is “wallet”?
2. HD Wallet (BIP32, 39, 44)
3. UTXO vs Account Model
Security
4. Private Key Security
5. How a Transaction is made
Usability
6. Mnemonic Recovery
7. Add/Create Token
8. ERC20MetaInfo

3. General Knowledge
3

4. Wallet
4

5. 1. What is “wallet”
100 ETH0x7e5f4552091a69125d5dfcb7b8c2659029395bdf
Blockchain Bitcoin Ethereum
15 ETH0x3738560173bade58bba4d79e1749a8b6373856
70 ETH0xb26fc5e385ed936623fb54bae4ff0b9476094d92

6. 1. What is “wallet”
•
• bitFlyer, Binance, Coincheck, Zaif, etc
• Web
• Blockchain.info, MyEtherWallet, etc
• PC
• Electrum, Exodus, Armory, MetaMask
•
• Jaxx, Tachyon, imToken, tokenPocket, Toshi, Chipher, Ginco, etc
•
• Trezor, Ledger Nano, CoolWallet
•

7. 1. What is “wallet”
API
Blockchain
0x7e5f4552091a69125d5dfcb7b8c2659029395bdf
0x3e5f....fde7
0x4c60....6dfe
0xf3afb...b94c
…
0x7e5f....5bdf
Wrooooooong!!

8. 1. What is “wallet”
2
2 = 1,461,501,637,330,902,918,203,684,832,716,283,019,655,932,542,976
160
160

9. 1. What is “wallet”
2
2 = 1,461,501,637,330,902,918,203,684,832,716,283,019,655,932,542,976
160
160
Private Key Public Key

10. 1. What is “wallet”
Private Key Public Key
0x7e5f4552091a69125d5dfcb7b8c2659029395bdf
☓ ☓
(*1)

11. 1. What is “wallet”
10
10
10
48
50
80

12. 2. HD Wallet (BIP32, 39, 44)
• HD = Hierarchy Deterministic
• HD “ ”
•
http://blockchain.gunosy.io/entry/2017/12/21/165314
BIP 39
BIP 32 BIP 44

13. 3. UTXO vs Account Model
Bitcoin UTXO
Ethereum Account / Balance Model
1 BTC
12xCUJYdCVSJph6BpHkgfMjVzp8LuUpwas
15 ETH
0x3738560173bade58bba4d79e1749a8b6373856
5 BTC 2 BTC
2 BTC 6 BTC
80 BTC
1LaC89iueNjzQgbFMUVPoaBQeLcQJ2VZD
1 BTC 1 BTC
1 BTC 2 BTC
0x7e5f4552091a69125d5dfcb7b8c2659029395bdf
0x3738560173bade58bba4d79e1749a8b6373856
0x7e5f4552091a69125d5dfcb7b8c2659029395bdf
0x3738560173bade58bba4d79e1749a8b6373856
99 ETH
2 ETH
56 ETH
12 ETH
UTXO Model Account/Balance Model
3 BTC
10 ETH
7 ETH

14. 3. UTXO vs Account Model
Bitcoin UTXO
Ethereum Account / Balance Model
1 BTC
12xCUJYdCVSJph6BpHkgfMjVzp8LuUpwas
15 ETH
0x3738560173bade58bba4d79e1749a8b6373856
5 BTC
2 BTC 6 BTC
80 BTC
1LaC89iueNjzQgbFMUVPoaBQeLcQJ2VZD
1 BTC 1 BTC
2 BTC
0x7e5f4552091a69125d5dfcb7b8c2659029395bdf
0x3738560173bade58bba4d79e1749a8b6373856
0x7e5f4552091a69125d5dfcb7b8c2659029395bdf
0x3738560173bade58bba4d79e1749a8b6373856
99 ETH
2 ETH
56 ETH
12 ETH
UTXO Model Account/Balance Model
3 BTC
10 ETH
7 ETH
2 BTC
1 BTC
2 ETH
20 ETH
UTXO

15. 3. UTXO vs Account Model
Bitcoin UTXO
Ethereum Account / Balance Model
1 BTC
12xCUJYdCVSJph6BpHkgfMjVzp8LuUpwas
15 ETH
0x3738560173bade58bba4d79e1749a8b6373856
5 BTC 2 BTC
2 BTC 6 BTC
80 BTC
1LaC89iueNjzQgbFMUVPoaBQeLcQJ2VZD
1 BTC 1 BTC
1 BTC 2 BTC
0x7e5f4552091a69125d5dfcb7b8c2659029395bdf
0x3738560173bade58bba4d79e1749a8b6373856
0x7e5f4552091a69125d5dfcb7b8c2659029395bdf
0x3738560173bade58bba4d79e1749a8b6373856
99 ETH
2 ETH
56 ETH
12 ETH
UTXO Model Account/Balance Model
3 BTC
1 BTC
3 BTC
2 BTC
2 BTC
UTXO
4 BTC

16. 3. UTXO vs Account Model
Bitcoin UTXO
Ethereum Account / Balance Model
1 BTC
12xCUJYdCVSJph6BpHkgfMjVzp8LuUpwas
15 ETH
0x3738560173bade58bba4d79e1749a8b6373856
5 BTC 2 BTC
2 BTC 6 BTC
80 BTC
1LaC89iueNjzQgbFMUVPoaBQeLcQJ2VZD
1 BTC 1 BTC
1 BTC 2 BTC
0x7e5f4552091a69125d5dfcb7b8c2659029395bdf
0x3738560173bade58bba4d79e1749a8b6373856
0x7e5f4552091a69125d5dfcb7b8c2659029395bdf
0x3738560173bade58bba4d79e1749a8b6373856
99 ETH
2 ETH
56 ETH
12 ETH
UTXO Model Account/Balance Model
3 BTC
0.5 BTC 0.5 BTC
0.5 BTC

17. Security
17

18. Transaction
18

19. 5. How a Transaction is made
Geth (Ethereum Client) Transaction
Ethereum Network
transfer(A→B, 0.2 ETH)
transactionPrivate Key
(signTransaction)
Tx
Geth Console

20. 5. How a Transaction is made
Transaction

21. 5. How a Transaction is made
Transaction
DB
DB

22. 5. How a Transaction is made
Transfer( →A, 10 ETH)
transaction
Private Key
Blockchain Network
Blockchain

23. 5. How a Transaction is made
Ethereum Network
Mobile App
Web Server
Geth
transfer(A→B, 0.2 ETH)
transaction
Private Key
(signTransaction)
Web 2.0
Web App (UI)
HTTP
Private Key
Tx
Web Server
Private Key
Web Server

24. 5. How a Transaction is made
Ethereum Network
Mobile App Hosted Client
e.g. Infura,
Metamask,
MyEtherWallet,
etc
JSON RPC
(web3.js)
Geth
transfer(A→B, 0.2 ETH)
transactionPrivate Key
(signTransaction)
Tx
Hosted Client
Tx
Private Key
(Local/Private Wallet)

25. Private Key
25

26. 4. Private Key Security

27. 4. Private Key Security MetaMask
Ethereum Network
Hosted Client
e.g. Infura,
Metamask,
MyEtherWallet,
etc
JSON RPC
(web3.js)
Geth/Parity
Web App (UI)
Private Key
transfer(A→B, 0.2 ETH)
Private Key
Local Storage

28. 4. Private Key Security Mobile Wallet
Ethereum Network
Mobile App Hosted Client
e.g. Infura,
Metamask,
MyEtherWallet,
etc
JSON RPC
(web3.js)
Geth/Parity
Keychain
Private Key
transfer(A→B, 0.2 ETH)
Face ID
Keychain

29. 4. Private Key Security
https://docs.microsoft.com/zh-tw/xamarin/ios/platform/touchid
transfer(A→B, 0.2 ETH)
transaction
Secure Enclave
Private Key
Private Key
Transaction

30. Usability
30

31. 6. Mnemonic Recovery

32. 8. Mnemonic Recovery
Mnemonic

33. 7. Add Token
ERC20

34. 7. Add Token

35. 7. Create Token

37. 8. ERC20MetaInfo