DocumentHashRegistry

The DocumentHashRegistry contract is designed to store and manage hashes of documents. Its main function, updateDocumentHashes, can only be called by the admin and is used to add/update or remove existing document hashes.

ExtendedERC20

This implements additional functionalities on top of the ERC-20 standard. It allows the admin to blacklist and KYC addresses. The following changes are noted:

• The transfer function has been modified to check if the sender and receiver are blacklisted/KYC'd.

• The transferFrom function has been modified to check if the sender and receiver are blacklisted/KYC'd.

• The mint function checks if the receiver is blacklisted/KYC'd. It can only be called by the admin.

It also introduces the following main actors within the system:

• DEFAULT_ADMIN_ROLE — Overall contract administrator

• PAUSER_ROLE — Can pause/unpause token transfers

• MINTER_ROLE — Can create new tokens

• WIPER_ROLE — Can burn tokens from any account

• KYC_ROLE — Manages KYC approvals

• UPGRADER_ROLE — Can upgrade the contract

With the key important state transitions being

• Minting — Increases the total supply and recipient's balance

• Burning/Wiping — Decreases total supply and account's balance

• Pausing — Halts all token transfers

• Changing KYC/Blacklist status — Affects transfer permissions