This document discusses porting native blockchain libraries to mobile apps using React Native. It describes how React Native allows sharing code between iOS and Android while integrating native functionality. It then explains how the Elastos blockchain project has developed native C++ libraries for cryptocurrency wallet functions like signing, verification, and mnemonic generation. These libraries can be integrated into React Native apps through native modules, avoiding additional porting work and improving efficiency. It provides examples of using Objective-C++ for iOS and the Java Native Interface for Android to interface between JavaScript and the native C++ code.

1. Porting native blockchain
libraries to mobile with React
Native
Adem Bilican
adem@cansulting.ch
@ademcan_net

2. React Native
• JavaScript framework to build mobile apps
• Share code between iOS and Android (and web)
• Easy integration of native code/lib
• Strong community
• Tons of npm packages available
• “native” feeling

3. Blockchain
• Distributed ledger
• Secure, transparent, trustless
• Core element of cryptocurrencies

4. React Native + Blockchain
relai.ch theqrl.org elastos.org

5. Elastos
• Blockchain project bringing the new SmartWeb
• Owning and sharing your data
• Owning and sharing/monetizing any digital asset
• Secure communication via a P2P network
• Crypto-currency used in the whole ecosystem

6. Native Modules
• Accessing native platform API
• Allows execution of native code from JS directly
• For example
• Calendar access
• Camera access

7. One step further
• Let’s bring some C++ library into our RN app
• Elastos builds native libraries for the crypto wallet functions
• Signing, verifying, generating mnemonic
• Why native libraries
• More efficient
• Maintained by the core team
• Always up-to-date
• Already available (no additional work required to port to JS)

8. One step further
JavaScript
Native SDK code
(c/cpp)
Native mobile code
(Objective-C /Java)
React Native

9. generateMnemonic()
• Mnemonic: list of 12 (to 24) words that contains the access to one’s
cryptocurrency wallet
• A list of public/private key pairs can be generated from the mnemonic
• Loosing mnemonic = loosing access to your wallet

10. Objective-C++ (iOS)
• Ojective-C++: Possible to write Objective-C code with c++ calls
• Update file extension to .mm (instead of .m)

11. Objective-C++ (iOS)

12. Java Native Interface (Android)
JavaScript
Java
JNI
C++

13. Java Native Interface (Android)

14. Thank you