Attestation Issuers Management List

StagnantStandards Track: ERC
Created: 2018-09-08
Weiwu Zhang <a@colourful.land>, James Sangalli <j.l.sangalli@gmail.com>
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In smart contracts, we will need methods to handle cryptographic attestations to a users identifier or abilities. Let's say we have a real estate agent, KiwiRealtors, that provides an "expression of interest" function though a smart contract and requires the users to provide an attestation that they are a resident of New Zealand or Australia, as a legal requirement. This has actually happened in the New Zealand property market and it is the perfect example of a need to handle such attestations.

However, it is not practical for a smart contract to explicitly trust an attestation issuer. There are multiple issuers who can provide an attestation to a person's residency - a local Justice of the Peace, the land title office, local police, passport authority etc. We envision a model where the effort to manage the list of qualified issuers is practically outsourced to a list.

Anyone can publish a list of issuers. Only the most trusted and carefully maintained lists gets popular use.


This ERC provides a smart contract interface for anyone to manage a list of attestation issuers. A smart contract would explicitly trust a list, and therefore all attestations issued by the issuers on the list.

Draft implementation

/* The purpose of this contract is to manage the list of attestation * issuer contracts and their capacity to fulfill requirements */ contract ManagedListERC { /* a manager is the steward of a list. Only he/she/it can change the * list by removing/adding attestation issuers to the list. * An issuer in the list is represented by their contract * addresses, not by the attestation signing keys managed by such a * contract. */ struct List { string name; string description; // short description of what the list entails string capacity; // serves as a filter for the attestation signing keys /* if a smart contract specifies a list, only attestation issued * by issuers on that list is accepted. Furthermore, if that * list has a non-empty capacity, only attestations signed by a * signing key with that capacity is accepted. */ address[] issuerContracts; // all these addresses are contracts, no signing capacity uint expiry; } // find which list the sender is managing, then add an issuer to it function addIssuer(address issuerContractAddress) public; //return false if the list identified by the sender doesn't have this issuer in the list function removeIssuer(address issuerContractAddress, List listToRemoveIssuerFrom) public returns(bool); /* called by services, e.g. Kiwi Properties or James Squire */ /* loop through all issuer's contract and execute validateKey() on * every one of them in the hope of getting a hit, return the * contract address of the first hit. Note that there is an attack * method for one issuer to claim to own the key of another which * is mitigated by later design. */ //loop through the issuers array, calling validate on the signingKeyOfAttestation function getIssuerCorrespondingToAttestationKey(bytes32 list_id, address signingKeyOfAttestation) public returns (address); /* for simplicity we use sender's address as the list ID, * accepting these consequences: a) if one user wish to maintain * several lists with different capacity, he or she must use a * different sender address for each. b) if the user replaced the * sender's key, either because he or she suspects the key is * compromised or that it is lost and reset through special means, * then the list is still identified by the first sender's * address. */ function createList(List list) public; /* replace list manager's key with the new key */ function replaceListIndex(List list, address manager) public returns(bool); }

Click here to see an example implementation of this ERC

#1387 #1386

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