# The YouGovern Secure Blockchain-Based Self-Sovereign Identity (SSI) Management and Access Control
## 4 Implementation
### Testing and Security  
Ensuring the reliability and security of the YouGovern platform involves comprehensive testing and security measures. All aspects of the smart contracts are covered by extensive testing using the Mocha and Chai frameworks, which help verify the functionality of all contract functions and their ability to handle errors effectively. Additionally, the smart contracts undergo rigorous security audits before launch to identify and rectify potential vulnerabilities, crucial for preventing issues like reentrancy attacks and ensuring the overall integrity of the platform.  
To comply with the W3C DID specification, YouGovern includes mechanisms for revocation and key rotation. Each DID stored on-chain is associated with an active status and version history. In case of key compromise, a user can revoke the current key by submitting a \"revokeDID0\" transaction, which deactivates the identifier. A subsequent \"rotateKey(newKey)\" transaction can then bind a new public key to the same identity. These functions are built into the system's smart contracts, ensuring transparency, traceability, and compliance with decentralized identity standards (see Listing 1).  
Access control in YouGovern is implemented through smart contract methods that allow users to authorize specific verifiers or entities to access selected credentials. The \"grantAccess0\" function allows a DID owner to whitelist an external address, while \"verifyData0\" allows verifiers to query authorized data (see Listing 2). These functions include appropriate role checks and event logging, and are protected by OpenZeppelin's Reen-trancyGuard to prevent recursive calls. We also ensure that gas limits are considered by optimizing contract storage and avoiding deep nesting in logic.  
Figure 9: IPFS Structure.  
```
functionrevokeDID(addressuser)publiconlyOwner{ didRecords[user].active=false; emitDIDRevoked(user); } functionrotateKey(addressoldKey,addressnewKey)publiconlyOwner{ require(!didRecords[oldKey].active,\"Oldkeymustbeevokedfirst\"); didRecords[newKey]=didRecords[oldKey]; didRecords[newKey].active=true; emitKeyRotated(oldKey,newKey); }
```  
Listing 1: DID revocation sample code.  
```
mapping(address=>mapping(address=>bool))publicaccessPermissions; functiongrantAccess(addressverifier)public{ accessPermissions[msg.sender][verifier]=true; emitAccessGranted(msg.sender,verifier); } functionverifyData(addressuser)publicviewreturns(stringmemory){ require(accessPermissions[user][msg.sender],\"Accessnotgranted\"); returndidRecords[user].dataHash; }
```  
Listing 2: Access control sample code.  
Upon completion of testing, the YouGovern system is deployed on the BSC mainnet. The selection of this network is due to its compatibility with Ethereum tools, enhanced transaction speed, and reduced costs. Post-deployment, the system is continuously monitored for performance and security issues, with regular updates applied to address new security threats and enhance functionalities.  
The user can create an account and log in to the platform. Figure 10 depicts YouGovern's client dashboard. Thereupon, the user can start uploading IPFSs (Figure 11), where access to them will be managed by YouGovern.  
Figure 10: Client Dashboard.