Humanbound onchain identity

A Humanbound Token (HBT) is an ERC721 standard NFT, which is an on-chain representation of an off-chain verified identity. While the smart contracts are designed specifically for Humanbound tokens, the services provided by www.humanbound.xyz rely heavily on Violet's identity platform and tools.

Violet is the platform and protocol on which Humanbound is built. 

Identity primitive

The core concept behind Humanbound tokens is that they are tied to a verified identity using multi-factor authentication (MFA), which provides identity continuity (rather than tying an identity or “soul” to a wallet). This makes HBT the first simple, privacy-preserving off-chain identity representation for web3.

Humanbound's design: 

1. mint tokens bound to an account upon identity verification, and 
2. verify that this account is tied to this confirmed identity.

Successful wallet authentication and subsequent identity confirmation triggers ERC721 minting in the user's wallet.

Registration of a second authentication factor ensures continuity of identity and is required later on, for example for identity changes. Initially, this is an SMS  one-time password (OTP).

To achieve its goal, HBTs must be associated with strong authentication. It's generally considered that strong authentication requires at least two of three categories: 

• knowledge (something you know, such as a password), 
• inherence (something you are, such as fingerprints), or 
• possession (something you own, such as your cell phone).

How Works Humanbound

1. Authenticate with your wallet and confirm ownership of your address with Sign In With Ethereum. 
2. Registration of phone number as the 2nd authentication factor using SMS OTP.
3. Registering and saving authentication factors such as wallet address and phone number.
4. KYC processing. Users provide their personal information (first and last name, nationality and date of birth) and upload a copy of their identity document. Identity verification using liveness detector is done by Persona.
5. The backend receives KYC data, sanctions list verification results and duplicate checks. The KYC provider returns the data including verified, personal and identity document information. Based on the PII provided, a “unique fingerprint” (hash) is created and compared to the fingerprints of all previously registered users. If the fingerprints match, registration is terminated.
6. Storage of encrypted PII. All personal information is stored in encrypted form. 
7. Deleting PII. Whether users complete the entire enrollment process or opt out at some point, triggers the deletion of all data associated with identity verification in Persona.
8. Return of an access token (EAT) as transaction authorization. The Violet assessment  service evaluates the system state and checks whether the user is correctly registered and meets the required criteria. If all indicators are green, the backend returns a signed Ethereum access token (EAT) to the frontend. This EAT grants the user the right to minе a specific Id token for their address.
9. Users are prompted to sign the minеing transaction with their private key.
10. The Humanbound token is minted with EAT. The gas consumed during the transaction is reimbursed. EAT is sent as part of the transaction, and the token is minted.
     

Humanbound ERC721 contract

Violet Humanbound Tokens, also known as HBT, are ERC721 tokens with some specific characteristics. The main ones are transfer restrictions and modularity through the use of the Extendable framework.

The “stack” of HBT smart contracts consists of different levels:

• Humanbound Contract
• ERC721 Extendable
• Extendable Framework

Extendable contracts provide the capabilities needed to extend and update an HBT smart contract using modular blocks called extensions. Contracts are based on OpenZeppelin's implementation of ERC721 and adapted for compatibility with the Extendable Framework:

Extensions are state-less smart contracts that contain logic and reuse functions. This is what you extend an Extendable contract with.

The Humanbound Token contract is built using the Extendable Framework. Thus, all HBT-specific logic and functions are placed in different extensions:

• Ethereum access token (aka EAT) is a mechanism that allows a user to perform certain actions on the blockchain defined by the EAT issuer. It works as follows: the issuer signs a smart contract function call and its parameters. The user then sends his transaction along with the generated signature. Checks are performed on the chain to ensure the integrity of the transaction data (function parameters) and that the signer matches the intended issuer. EATs also contain expiration times, which are checked on the chain.
• Humanbound token URI logic. This extension defines how the URIs of Humanbound tokens are handled. By default, all tokens return the same generic URI, called baseURI, unless a specific token URI is overridden.
• Humanbound Mint Logic extension contains logic for minting Humanbound tokens.
• Humanbound Burn Logic allows Humanbound tokens to be burned by the owner of a Humanbound smart contract or the owner of the token.
• Humanbound token transfer logic. By default, Humanbound tokens are not transferable. Therefore, the transfer functions included in the EIP-721 interfaces are configured to return when called. However, because Humanbound tokens are bound to a person rather than an address, token transfer may be possible in some circumstances. For example, if a user loses control of the address to which their Humanbound token belongs, it may be possible to run a procedure (still manual) to recover it.
• Humanbound Gas Refund Logic in Ethereum Mainnet. This works by refunding the transaction value during a successful minting session. Any failed mints (either due to failed EAT verification or other reasons) will not be refunded to avoid denial of service attacks. They are currently using gas estimations, so refunds will cover 99% of the transaction value.

HumanBound Use Cases

Fair airdrops. You can set a quota - the maximum number of addresses for which one person (one HBT) can claim an airdrop. This will save you from having to analyze the data to weed out large clusters of addresses belonging to the same person and trying to cheat.

Customizable on-chain, identity-related compliance.

Proof of Humanity. When a person tries to register their identity, it is verified, while maintaining privacy, that they aren't already registered. This is to prevent users from creating multiple identities. Humanbound actually becomes a unique proof of humanity.

Voting. The governance of Protocols in cryptocurrency is dominated by the “coin voting” system, in which the right to vote is determined by the number of a project's own tokens. HBT can be used to simply enforce the “1 person, 1 vote” principle. Or in a more complex system, possession of HBT can serve as a data point for calculating the weight of a vote or simply as a minimum requirement for voting.