EToken Program

Overview

The EToken Program work as a wrapper program on top of existing token program. It contains methods which enables transfer, minting, burning of encrypted tokens.

Encrypted Data Types

• Euint64: Encrypted 64-bit unsigned integer representing token amounts

  pub struct Euint64 {
      pub handle: u128,
      pub proof: Vec<u8>,
      pub ctx: Vec<u8>,
  }

• EAddress: Encrypted address representation for anonymous transfers

  pub struct EAddress {
      pub handle: u128,
  }

• Ebool: Encrypted boolean for conditional operations

  pub struct Ebool {
      pub handle: u128,
  }

• Einput: Generic encrypted input that can be converted to other types

  pub struct Einput {
      pub handle: u128,
      pub proof: Vec<u8>,
  }

Account Types

• EMint: Encrypted mint account storing token metadata and supply

  pub struct EMint {
      pub mint: Pubkey,                    // Associated SPL token mint
      pub authority: Pubkey,               // Mint authority
      pub supply: u64,                     // Total supply (plaintext)
      pub decimals: u8,                    // Token decimals
      pub is_initialized: bool,            // Initialization status
      pub freeze_authority: Option<Pubkey>, // Freeze authority
      pub is_frozen: bool,                 // Freeze status
  }

• ETokenAccount: Encrypted token account storing user balances (created for every user)

  
  pub struct ETokenAccount {
      pub mint: Pubkey,
      pub owner: Pubkey,
      pub amount: Euint64,
      pub delegate: Option<Pubkey>,
      pub is_initialized: bool,
      pub is_frozen: bool,
  }

Functions and Use Cases

initialize_mint

• Params
  • decimals: u8
  • authority: Pubkey
• Purpose: Creates a new encrypted token mint account for a given SPL token.
• Use Case: Initializes account for a certain mint address
• Process
  • Creates an EMint PDA with seeds [b"emint", mint.key()]
  • Sets up mint metadata (decimals, authority, freeze authority)
  • Initializes supply to 0
  • Sets freeze authority to the provided authority

initialize_account

• Params
  • owner: Pubkey
• Purpose: Creates a new encrypted token account for a user which will hold encrypted tokens (pointer) for certain token for user.
• Use Case: Intializes account for user to store encrypted token pointers.
• Process:
  • Creates an ETokenAccount PDA with seeds [b"eaccount", emint.key(), owner]
  • Initializes with zero encrypted balance using Euint64::balance_handle()
  • Sets owner and mint association
  • Initializes delegate as None
  • Only payer can initialize

mint_to

• Params
  • to: Pubkey - Recipient account owner
  • amount: u64 - Amount to mint (plaintext)
• Purpose: Mints encrypted tokens to a user's account.
• Process:
  • Converts plaintext amount to encrypted Euint64
  • Adds encrypted amount to recipient's balance using homomorphic addition
  • Updates mint supply
  • Sets access control for the new balance
  • Enforces maximum supply limit (1 billion tokens)

burn

• Params
  • to: Pubkey - Account owner (for access control)
  • amount: Einput - Encrypted amount to burn
• Purpose: Burns encrypted tokens from a user's account.
• Process:
  • Verifies that the user has sufficient balance using encrypted comparision (le (less equal))
  • Subtracts encrypted amount using (PET.sub)
  • Updates account balance
  • Sets access control for the new balance
  • Returns the actual burned amount

etransfer

• Params
  • receiver: Pubkey - Recipient account owner
  • amount: Einput - Encrypted amount to transfer
• Purpose: Transfers encrypted tokens between accounts.
• Process:
  • Verifies sender has sufficient balance.
  • Performs encrypted subtraction from sender using PET.sub.
  • Performs encrypted addition to receiver using PET.add.
  • Updates both account balances for both sender and receiver account.
  • Sets access control for both accounts.