isin-lib-solidity

A Solidity library for efficient and reversible conversion between International Securities Identification Numbers (ISINs) as strings and uint256 values directly within EVM smart contracts.

This library is crucial for smart contracts that need to manage or reference financial instruments identified by ISINs, enabling a direct and gas-optimized link between off-chain ISIN strings and on-chain uint256 identifiers.

Why This Library Matters

Financial instruments use 12-character alphanumeric ISINs for global identification. Smart contracts on EVM blockchains, however, primarily use uint256 for unique IDs (like NFT tokenIds). This data type mismatch can be a hurdle. isin-lib-solidity provides a gas-efficient, on-chain solution using base36 encoding to convert ISIN strings to uint256 and back. This ensures a reliable one-to-one mapping, vital for integrating traditional financial assets with DeFi applications directly on the blockchain.

Features

• Converts ISIN strings (must be uppercase A-Z, 0-9, and 12 characters long) to uint256.
• Converts uint256 values back to 12-character ISIN strings, padding with leading zeros if necessary.
• Uses base36 encoding, implemented with gas optimization in mind for Solidity.
• Includes input validation for ISIN string format and length.
• Designed as a library for easy integration into other smart contracts.

Installation

Using a package manager (e.g., npm/yarn for Hardhat/Truffle projects):

npm install your-package-name # Or your actual package name
# or
yarn add your-package-name # Or your actual package name

Then import in your Solidity contract:

// Adjust path if your package structure is different
import "your-package-name/contracts/ISINLib.sol";

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "./ISINLib.sol"; // Or from node_modules if installed

contract FinancialProductRegistry {
  mapping(uint256 => string) public idToIsinString;
  mapping(string => uint256) public isinStringToId; // Be mindful of gas costs for string keys

  event ProductRegistered(
    string indexed isinString,
    uint256 indexed instrumentId
  );

  /**
   * @notice Registers a product using its ISIN string.
   * @param isinString The ISIN of the product as a 12-character string (uppercase A-Z, 0-9).
   */
  function registerProduct(string memory isinString) public {
    // The ISINLib.toUint256 function already requires 12 chars.
    // Additional check for empty string can be done if needed, though ISINLib will revert.
    // require(bytes(isinString).length > 0, "ISINLib: ISIN string cannot be empty");
    require(
      isinStringToId[isinString] == 0,
      "ISINLib: Product already registered with this ISIN"
    );

    uint256 instrumentId = ISINLib.toUint256(isinString); // Library function call

    idToIsinString[instrumentId] = isinString;
    isinStringToId[isinString] = instrumentId;

    // --- Placeholder for NFT minting logic (e.g., ERC721 _mint) ---
    // _mint(msg.sender, instrumentId);
    // --- End Placeholder ---

    emit ProductRegistered(isinString, instrumentId);
  }

  /**
   * @notice Retrieves the ISIN string for a given instrument ID.
   * @param instrumentId The uint256 ID of the instrument.
   * @return The ISIN string.
   */
  function getIsinFromId(
    uint256 instrumentId
  ) public view returns (string memory) {
    string memory isinString = idToIsinString[instrumentId];
    // ISINLib.fromUint256(0) returns "000000000000".
    // If an ID 0 is not a valid instrumentId, or if empty string means not found:
    require(
      bytes(isinString).length > 0,
      "ISINLib: Instrument ID not found or ISIN is empty"
    );
    return isinString;
  }

  /**
   * @notice Retrieves the instrument ID for a given ISIN string.
   * @param isinString The ISIN string of the instrument.
   * @return The uint256 instrument ID.
   */
  function getIdFromIsin(
    string memory isinString
  ) public view returns (uint256) {
    uint256 instrumentId = isinStringToId[isinString];
    require(instrumentId != 0, "ISINLib: ISIN not found"); // Assumes ID 0 is not used for valid ISINs
    return instrumentId;
  }
}

API

The ISINLib.sol library provides the following core functions:

function toUint256(string memory isin) internal pure returns uint256 numericValue)

• Encodes an ISIN string to a uint256 value.
• Parameters:
  • isin (string memory): The ISIN string to encode (must be uppercase A-Z, 0-9, and 12 characters long).
• Returns: The uint256 representation of the ISIN.
• Reverts if the ISIN string is not 12 characters long or contains invalid characters.

function fromUint256(uint256 value) internal pure returns (string memory isin)

• Decodes a uint256 back to an ISIN string.
• Parameters:
  • value: The uint256 value to decode.
• Returns: The original ISIN string (12 characters, padded with leading '0's if necessary). "000000000000" for input 0.
• Reverts if the input value is greater than MAX_ISIN_VALUE (36^12 - 1).

Sister Libraries

This library can be complemented by similar libraries in other languages for consistent ISIN <=> uint256 conversion across different environments:

• For JavaScript/TypeScript front-end or Node.js applications https://github.com/webmobix/isin-lib-js
• For Java applications https://github.com/webmobix/isin-lib-java

Contributing

Contributions are welcome.