--- eip: 1484 title: Digital Identity Aggregator author: Anurag Angara , Andy Chorlian , Shane Hampton , Noah Zinsmeister discussions-to: https://github.com/ethereum/EIPs/issues/1495 status: Draft type: Standards Track category: ERC created: 2018-10-12 requires: 191 --- ## Simple Summary A protocol for aggregating digital identity information that's broadly interoperable with existing, proposed, and hypothetical future digital identity standards. ## Abstract This EIP proposes an identity management and aggregation framework on the Ethereum blockchain. It allows entities to claim an identity via a singular `Identity Registry` smart contract, associate this `Identity` with Ethereum addresses in a variety of meaningful ways, and use it to interface with smart contracts. This enables arbitrarily complex identity-related functionality. Notably (among other features) this proposal is [DID compliant](https://github.com/hydrogen-dev/ERC-1484/blob/master/best-practices/DID-Method.md), can natively support [ERC-725](https://github.com/hydrogen-dev/ERC-1484/tree/master/contracts/examples/Resolvers/ERC725) and [ERC-1056](https://github.com/hydrogen-dev/ERC-1484/tree/master/contracts/examples/Resolvers/ERC1056) identities, and lays a robust foundation for [meta-transactions](https://github.com/hydrogen-dev/ERC-1484/tree/master/contracts/examples/Providers/MetaTransactions). ## Motivation Emerging identity standards and related frameworks proposed by the Ethereum community (including ERCs/EIPs [725](https://github.com/ethereum/EIPs/issues/725), [735](https://github.com/ethereum/EIPs/issues/735), [780](https://github.com/ethereum/EIPs/issues/780), [1056](https://github.com/ethereum/EIPs/issues/1056), etc.) define and instrumentalize digital identity in a variety of ways. As existing approaches mature, new standards emerge, and isolated, non-standard approaches to identity develop, managing multiple identities will become increasingly burdensome and involve the unnecessary duplication of work. The proliferation of on-chain identity solutions can be traced back to the fact that each codifies a notion of identity and links it to specific aspects of Ethereum (claims protocols, per-identity smart contracts, signature verification schemes, etc.). This proposal eschews that approach, instead introducing a protocol layer in between the Ethereum network and individual identity applications. This solves identity management and interoperability challenges by enabling any identity-driven application to leverage an un-opinionated identity management protocol. ## Definitions - `Identity Registry`: A single smart contract which is the hub for all `Identities`. The primary responsibility of the `Registry` is to enforce a global namespace for `Identities`, which are individually denominated by Ethereum Identification Numbers (EINs). - `Identity`: A data structure containing all the information relevant to a particular identity. They are denominated by EINs (incrementing `uint`s), which are unique but uninformative. - `Associated Address`: An Ethereum address publicly associated with an `Identity`. In order for an address to become an `Associated Address` for an `Identity`, the `Identity` must produce signed messages from the candidate address and an existing `Associated Address` indicating this intent. Identities can remove an `Associated Address` by producing an appropriately signed message indicating intent to disassociate itself from the `Identity`. An address may only be an `Associated Address` for one `Identity` at any given time. - `Provider`: An Ethereum address (typically but not by definition a smart contract) authorized to add and remove `Associated Addresses`, `Providers`, and `Resolvers` from `Identities` who have authorized the `Provider` to act on their behalf. `Providers` exist to facilitate user adoption, and make it easier to manage `Identities`. - `Resolver`: A smart contract containing arbitrary information pertaining to `Identities`. A resolver may implement an identity standard, such as ERC-725, or may consist of a smart contract leveraging or declaring identifying information about `Identities`. These could be simple attestation structures or more sophisticated financial dApps, social media dApps, etc. Each `Resolver` added to an `Identity` makes the `Identity` more informative. - `Recovery Address`: An Ethereum address (either an account or smart contract) that can be used to recover lost identities as outlined in the [Recovery](#recovery) section. - `Poison Pill`: In the event of irrecoverable control of an `Identity`, the `Poison Pill` offers a contingency measure to permanently disable the `Identity`. It removes all `Associated Addresses` and `Providers` while preserving the `Identity` (and optionally, `Resolvers`). Evidence of the existence of the `Identity` persists, while control over the `Identity` is nullified. ## Specification A digital identity in this proposal can be viewed as an omnibus account, containing more information about an identity than any individual identity application could. This omnibus identity is resolvable to an unlimited number of sub-identities called `Resolvers`. This allows an atomic entity, the `Identity`, to be resolvable to abstract data structures, the `Resolvers`. `Resolvers` recognize `Identities` by any of their `Associated Addresses`, or by their `EIN`. The protocol revolves around claiming an `Identity` and managing `Associated Addresses` and `Resolvers`. Identities delegate much of this responsibility to one or more `Providers`. `Provider` smart contracts or addresses may add and remove `Resolvers` and `Providers` indiscriminately, but may only add and remove `Associated Addresses` with the appropriate permissions. ### Identity Registry The `Identity Registry` contains functionality to create new `Identities` and for existing `Identities` to manage their `Providers`, `Associated Addresses`, and `Resolvers`. It is important to note that this registry fundamentally requires transactions for every aspect of building out an `Identity`. However, recognizing the importance of accessibility to dApps and identity applications, we empower `Providers` to build out `Identities` on the behalf of users, without requiring users to pay gas costs. An example of this pattern, often referred to as a meta transactions, can be [seen in the reference implementation](https://github.com/hydrogen-dev/ERC-1484/tree/master/contracts/examples/Providers/MetaTransactions). Due to the fact that multiple addresses can be associated with a given identity (though not the reverse), `Identities` are denominated by `EIN`s. This `uint` identifier can be encoded in QR format or transformed into more user-intuitive formats, such as a `string`, in registries at the `Provider` or `Resolver` level. ### Address Management The address management function consists of trustlessly connecting multiple user-owned `Associated Addresses` to an `Identity`. It does not give special status to any particular `Associated Address`, rather leaving this specification to identity applications built on top of the protocol - for instance, `management`, `action`, `claim` and `encryption` keys denominated in the ERC-725 standard, or `identifiers` and `delegates` as denominated in ERC-1056. This allows a user to access common identity data from multiple wallets while still: - retaining flexibility to interact with contracts outside of their identity - taking advantage of address-specific permissions established at the application layer of a user's identity. Trustlessness in the address management function is achieved through a signature and verification scheme that requires two signatures - one from an address already within the registry and one from the address to be claimed. Importantly, the transaction need not come from the original user, which allows third parties (entities, governments, etc.) to bear the overhead of creating core identities. To prevent a compromised `Associated Address` from unilaterally removing other `Associated Addresses`, removal of an `Associated Address` also requires a signature from the address to be removed. All signatures required in ERC-1484 are designed per the [ERC-191](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-191.md) v0 specification. To avoid replay attacks, all signatures must include a timestamp within a rolling lagged window of the current `block.timestamp`. For more information, see this [best practices document](https://github.com/hydrogen-dev/ERC-1484/blob/master/best-practices/VerifyingSignatures.md) in the reference implementation. ### Provider Management While the protocol allows users to directly call identity management functions, it also aims to be more robust and future-proof by allowing `Providers`, typically arbitrary smart contracts, to perform identity management functions on a user's behalf. A `Provider` set by an identity can perform address management and resolver management functions by passing a user's `EIN` in function calls. In order to prevent `Identities` from adding an initial `Provider` that does not implement the functionality to add other `Providers` (this leaving the `Identity` 'stuck'), identities may add `Providers` directly from the `Identity Registry`. ### Resolver Management A `Resolver` is any smart contract that encodes information which resolves to an `Identity`. We remain agnostic about the specific information that can be encoded in a resolver and the functionality that this enables. The existence of resolvers is primarily what makes this ERC an identity *protocol* rather than an identity *application*. `Resolvers` resolve abstract data in smart contracts to an atomic entity, the `Identity`. ### Recovery The specification includes a `Recovery Address` for instances when users lose control over an `Associated Address`. Upon `Identity` creation, the public `Recovery Address` is passed as a parameter by the creator. Recovery functionality is triggered in three scenarios: **1. Changing Recovery Address**: If a recovery key is lost, a `Provider` can [triggerRecoveryAddressChangeFor](#triggerRecoveryAddressChangeFor) through a `Provider`. To prevent malicious behavior from someone who has gained control of an `Associated Address` or `Provider` and is changing the `Recovery Address` to one under their control, this action triggers a 14 day challenge period during which the old `Recovery Address` may reject the change. If the `Recovery Address` does not reject the change within 14 days, the `Recovery Address` is changed. Old `Recovery Address` reject the change by can dispute the change request by calling [triggerRecovery](#triggerrecovery). **2. Recovery**: Recovery occurs when a user recognizes that an `Associated Address` or the `Recovery Address` belonging to the user is lost or stolen. In this instance a `Recovery Address` must call [triggerRecovery](#triggerrecovery). This removes all `Associated Addresses` and `Providers` from the corresponding `Identity` and replaces them with an address passed in the function call. The `Identity` and associated `Resolvers` maintain integrity. The user is now responsible for adding the appropriate un-compromised addresses back to their `Identity`. *Importantly, the `Recovery Address` can be a user-controlled wallet or another address such as a multisig wallet or smart contract. This allows for arbitrarily sophisticated recovery logic! This includes the potential for recovery to be fully compliant with standards such as [DID](https://decentralized.id/).* **3. Poison Pill** The Recovery scheme offers considerable power to a `Recovery Address`; accordingly, the `Poison Pill` is a nuclear option to combat malicious control over an `Identity` when a `Recovery Address` is compromised. If a malicious actor compromises a user's `Recovery Address` and triggers recovery, any address removed in the `Recovery` process can call [triggerPoisonPill](#triggerPoisonPill) within 14 days to permanently disable the `Identity`. The user would then need to create a new `Identity`, and would be responsible for engaging in recovery schemes for any identity applications built in the `Resolver` or `Provider` layers. #### Alternative Recovery Considerations We considered many possible alternatives when devising the Recovery process outlined above. We ultimately selected the scheme that was most un-opinionated, modular, and consistent with the philosophy behind the `Associated Address`, `Provider`, and `Resolver` components. Still, we feel that it is important to highlight some of the other recovery options we considered, to provide a rationale as to how we settled on what we did. **High Level Concerns** Fundamentally, a Recovery scheme needs to be resilient to a compromised address taking control of a user's `Identity`. A secondary concern is preventing a compromised address from maliciously destroying a user's identity due to off-chain utility, which is not an optimal scenario, but is strictly better than if they've gained control. **Alternative 1: Nuclear Option** This approach would allow any `Associated Address` to destroy an `Identity` whenever another `Associated Address` is compromised. While this may seem severe, we strongly considered it because this ERC is an identity *protocol*, not an identity *application*. This means that though a user's compromised `Identity` is destroyed, they should still have recourse to whatever restoration mechanisms are available in each of their actual identities at the `Resolver` and/or `Provider` level. We ultimately dismissed this approach for two main reasons: - It is not robust in cases where a user has only one `Associated Address` - It would increase the frequency of recovery requests to identity applications due to its unforgiving nature. **Alternative 2: Unilateral Address Removal via Providers** This would allow `Providers` to remove an `Associated Address` without a signature from said address. This implementation would allow `Providers` to include arbitrarily sophisticated schemes for removing a rogue address - for instance, multi-sig requirements, centralized off-chain verification, user controlled master addresses, deferral to a jurisdictional contract, and more. To prevent a compromised `Associated Address` from simply setting a malicious `Provider` to remove un-compromised addresses, it would have required a waiting period between when a `Provider` is set and when they would be able to remove an `Associated Address`. We dismissed this approach because we felt it placed too high of a burden on `Providers`. If a `Provider` offered a sophisticated range of functionality to a user, but post-deployment a threat was found in the Recovery logic of the provider, `Provider`-specific infrastructure would need to be rebuilt. We also considered including a flag that would allow a user to decide whether or not a `Provider` may remove `Associated Addresses` unilaterally. Ultimately, we concluded that only allowing removal of `Associated Addresses` via the `Recovery Address` enables equally sophisticated recovery logic while separating the functionality from `Providers`, leaving less room for users to relinquish control to potentially flawed implementations. ## Rationale We find that at a protocol layer, identities should not rely on specific claim or attestation structures, but should instead be a part of a trustless framework upon which arbitrarily sophisticated claim and attestation structures may be built. The main criticism of existing identity solutions is that they're overly restrictive. We aim to limit requirements, keep identities modular and future-proof, and remain un-opinionated regarding any functionality a particular identity component may have. This proposal gives users the option to interact on the blockchain using an arbitrarily robust `Identity` rather than just an address. ## Implementation **The reference implementation for ERC-1484 may be found in [hydrogen-dev/ERC-1484](https://github.com/hydrogen-dev/ERC-1484).** #### identityExists Returns a `bool` indicating whether or not an `Identity` denominated by the passed `EIN` exists. ```solidity function identityExists(uint ein) public view returns (bool); ``` #### hasIdentity Returns a `bool` indicating whether or not the passed `_address` is associated with an `Identity`. ```solidity function hasIdentity(address _address) public view returns (bool); ``` #### getEIN Returns the `EIN` associated with the passed `_address`. Throws if the address is not associated with an `EIN`. ```solidity function getEIN(address _address) public view returns (uint ein); ``` #### isAssociatedAddressFor Returns a `bool` indicating whether or not the passed `_address` is associated with the passed `EIN`. ```solidity function isAssociatedAddressFor(uint ein, address _address) public view returns (bool); ``` #### isProviderFor Returns a `bool` indicating whether or not the passed `provider` has been set by the passed `EIN`. ```solidity function isProviderFor(uint ein, address provider) public view returns (bool); ``` #### isResolverFor Returns a `bool` indicating whether or not the passed `resolver` has been set by the passed `EIN`. ```solidity function isResolverFor(uint ein, address resolver) public view returns (bool); ``` #### getIdentity Returns the `recoveryAddress`, `associatedAddresses`, `providers` and `resolvers` of the passed `EIN`. ```solidity function getIdentity(uint ein) public view returns (address recoveryAddress, address[] associatedAddresses, address[] providers, address[] resolvers); ``` #### createIdentity Creates an `Identity`, setting the `Provider` to the `msg.sender`. Returns the `EIN` of the new `Identity`. ```solidity function createIdentity(address recoveryAddress, address provider, address[] resolvers) public returns (uint ein); ``` Triggers event: [IdentityCreated](#identitycreated) #### createIdentityDelegated Preforms the same logic as `createIdentity`, but is called by a `Provider`. This function requires a signature for the `associatedAddress` to confirm their consent. ```solidity function createIdentityDelegated( address recoveryAddress, address associatedAddress, address[] resolvers, uint8 v, bytes32 r, bytes32 s, uint timestamp ) public returns (uint ein); ``` Triggers event: [IdentityCreated](#identitycreated) #### addAssociatedAddressDelegated Adds the `addressToAdd` to the `EIN` of the `approvingAddress`. Requires signatures from both the `approvingAddress` and the `addressToAdd`. ```solidity function addAssociatedAddressDelegated( address approvingAddress, address addressToAdd, uint8[2] v, bytes32[2] r, bytes32[2] s, uint[2] timestamp ) public; ``` Triggers event: [AssociatedAddressAdded](#associatedaddressadded) #### removeAssociatedAddressDelegated Removes the `addressToRemove` from its associated `EIN`. Requires a signature from the `addressToRemove`. ```solidity function removeAssociatedAddressDelegated( address addressToRemove, uint8 v, bytes32 r, bytes32 s, uint timestamp ) public; ``` Triggers event: [AssociatedAddressRemoved](#associatedaddressremoved) #### addProviders Adds an array of `Providers` to the `Identity` of the `msg.sender`. ```solidity function addProviders(address[] providers) public; ``` Triggers event: [ProviderAdded](#provideradded) #### addProvidersFor Preforms the same logic as `addProviders`, but is called by a `Provider`. ```solidity function addProvidersFor(uint ein, address[] providers) public; ``` Triggers event: [ProviderAdded](#provideradded) #### removeProviders Removes an array of `Providers` from the `Identity` of the `msg.sender`. ```solidity function removeProviders(address[] providers) public; ``` Triggers event: [ProviderRemoved](#providerremoved) #### removeProvidersFor Preforms the same logic as `removeProviders`, but is called by a `Provider`. ```solidity function removeProvidersFor(uint ein, address[] providers) public; ``` Triggers event: [ProviderRemoved](#providerremoved) #### addResolversFor Adds an array of `Resolvers` to the passed `EIN`. This must be called by a `Provider`. ```solidity function addResolversFor(uint ein, address[] resolvers) public; ``` Triggers event: [ResolverAdded](#resolveradded) #### removeResolversFor Removes an array of `Resolvers` from the passed `EIN`. This must be called by a `Provider`. ```solidity function removeResolversFor(uint ein, address[] resolvers) public; ``` Triggers event: [ResolverRemoved](#resolverremoved) #### triggerRecoveryAddressChangeFor Initiates a change in the current `recoveryAddress` for a given `EIN`. ```solidity function triggerRecoveryAddressChangeFor(uint ein, address newRecoveryAddress) public; ``` Triggers event: [RecoveryAddressChangeTriggered](#RecoveryAddressChangeTriggered) #### triggerRecovery Triggers `EIN` recovery from the current `recoveryAddress`, or the old `recoveryAddress` if changed within the last 2 weeks. ```solidity function triggerRecovery(uint ein, address newAssociatedAddress, uint8 v, bytes32 r, bytes32 s, uint timestamp) public; ``` Triggers event: [RecoveryTriggered](#recoverytriggered) #### triggerPoisonPill Triggers the poison pill on an `EIN`. This renders the `Identity` permanently unusable. ```solidity function triggerPoisonPill(uint ein, address[] firstChunk, address[] lastChunk, bool clearResolvers) public; ``` Triggers event: [IdentityPoisoned](#IdentityPoisoned) ### Events #### IdentityCreated MUST be triggered when an `Identity` is created. ```solidity event IdentityCreated( address indexed initiator, uint indexed ein, address recoveryAddress, address associatedAddress, address provider, address[] resolvers, bool delegated ); ``` #### AssociatedAddressAdded MUST be triggered when an address is added to an `Identity`. ```solidity event AssociatedAddressAdded( address indexed initiator, uint indexed ein, address approvingAddress, address addedAddress ); ``` #### AssociatedAddressRemoved MUST be triggered when an address is removed from an `Identity`. ```solidity event AssociatedAddressRemoved(address indexed initiator, uint indexed ein, address removedAddress); ``` #### ProviderAdded MUST be triggered when a provider is added to an `Identity`. ```solidity event ProviderAdded(address indexed initiator, uint indexed ein, address provider, bool delegated); ``` #### ProviderRemoved MUST be triggered when a provider is removed. ```solidity event ProviderRemoved(address indexed initiator, uint indexed ein, address provider, bool delegated); ``` #### ResolverAdded MUST be triggered when a resolver is added. ```solidity event ResolverAdded(address indexed initiator, uint indexed ein, address resolvers); ``` #### ResolverRemoved MUST be triggered when a resolver is removed. ```solidity event ResolverRemoved(address indexed initiator, uint indexed ein, address resolvers); ``` #### RecoveryAddressChangeTriggered MUST be triggered when a recovery address change is triggered. ```solidity event RecoveryAddressChangeTriggered( address indexed initiator, uint indexed ein, address oldRecoveryAddress, address newRecoveryAddress ); ``` #### RecoveryTriggered MUST be triggered when recovery is triggered. ```solidity event RecoveryTriggered( address indexed initiator, uint indexed ein, address[] oldAssociatedAddresses, address newAssociatedAddress ); ``` #### IdentityPoisoned MUST be triggered when an `Identity` is poisoned. ```solidity event IdentityPoisoned(address indexed initiator, uint indexed ein, address recoveryAddress, bool resolversReset); ``` ### Solidity Interface ```solidity interface ERC1484 { // Identity View Functions ///////////////////////////////////////////////////////////////////////////////////////// function identityExists(uint ein) external view returns (bool); function hasIdentity(address _address) external view returns (bool); function getEIN(address _address) external view returns (uint ein); function isAssociatedAddressFor(uint ein, address _address) external view returns (bool); function isProviderFor(uint ein, address provider) external view returns (bool); function isResolverFor(uint ein, address resolver) external view returns (bool); function getIdentity(uint ein) external view returns (address recoveryAddress, address[] associatedAddresses, address[] providers, address[] resolvers); // Identity Management Functions /////////////////////////////////////////////////////////////////////////////////// function createIdentity(address recoveryAddress, address provider, address[] resolvers) external returns (uint ein); function createIdentityDelegated( address recoveryAddress, address associatedAddress, address[] resolvers, uint8 v, bytes32 r, bytes32 s, uint timestamp ) external returns (uint ein); function addAssociatedAddressDelegated( address approvingAddress, address addressToAdd, uint8[2] v, bytes32[2] r, bytes32[2] s, uint[2] timestamp ) external; function removeAssociatedAddressDelegated( address addressToRemove, uint8 v, bytes32 r, bytes32 s, uint timestamp ) external; function addProviders(address[] providers) external; function addProvidersFor(uint ein, address[] providers) external; function removeProviders(address[] providers) external; function removeProvidersFor(uint ein, address[] providers) external; function addResolversFor(uint ein, address[] resolvers) external; function removeResolversFor(uint ein, address[] resolvers) external; // Recovery Management Functions /////////////////////////////////////////////////////////////////////////////////// function triggerRecoveryAddressChangeFor(uint ein, address newRecoveryAddress) external; function triggerRecovery(uint ein, address newAssociatedAddress, uint8 v, bytes32 r, bytes32 s) external; function triggerPoisonPill(uint ein, address[] firstChunk, address[] lastChunk, bool clearResolvers) external; // Events ////////////////////////////////////////////////////////////////////////////////////////////////////////// event IdentityCreated( address indexed initiator, uint indexed ein, address recoveryAddress, address associatedAddress, address provider, address[] resolvers, bool delegated ); event AssociatedAddressAdded (address indexed initiator, uint indexed ein, address approvingAddress, address addedAddress); event AssociatedAddressRemoved (address indexed initiator, uint indexed ein, address removedAddress); event ProviderAdded (address indexed initiator, uint indexed ein, address provider, bool delegated); event ProviderRemoved (address indexed initiator, uint indexed ein, address provider, bool delegated); event ResolverAdded (address indexed initiator, uint indexed ein, address resolvers); event ResolverRemoved (address indexed initiator, uint indexed ein, address resolvers); event RecoveryAddressChangeTriggered( address indexed initiator, uint indexed ein, address oldRecoveryAddress, address newRecoveryAddress ); event RecoveryTriggered( address indexed initiator, uint indexed ein, address[] oldAssociatedAddresses, address newAssociatedAddress ); event IdentityPoisoned (address indexed initiator, uint indexed ein, address recoveryAddress, bool resolversReset); } ``` ## Backwards Compatibility `Identities` established under this standard consist of existing Ethereum addresses; accordingly, there are no backwards compatibility issues. Deployed, non-upgradeable smart contracts that wish to become `Resolvers` for `Identities` will need to write wrapper contracts that resolve addresses to `EIN`-denominated `Identities`. ## Additional References - [ERC-1484 Reference Implementation](https://github.com/hydrogen-dev/ERC-1484) - [ERC-191 Signatures](https://github.com/ethereum/EIPs/issues/191) - [ERC-725 Identities](https://github.com/ethereum/EIPs/issues/725) - [ERC-1056 Identities](https://github.com/ethereum/EIPs/issues/1056) ## Copyright Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).