EIPs/EIPS/eip-725.md

---
eip: 725
title: Proxy Identity
author: Fabian Vogelsteller (@frozeman)
discussions-to: https://github.com/ethereum/EIPs/issues/725
status: Draft
type: Standards Track
category: ERC
created: 2017-10-02
---

## Simple Summary
A proxy contract for key management and execution, to establish a Blockchain identity.

## Abstract
The following describes standard functions for a unique identity for humans, groups, objects and machines.
This identity can hold keys to sign actions (transactions, documents, logins, access, etc), and claims, which are attested from third parties (issuers) and self-attested ([#ERC735](https://github.com/ethereum/EIPs/issues/735)), as well as a proxy function,  to act directly on the blockchain.

## Motivation
This standardized identity interface will allow Dapps, smart contracts and third parties to check the validity of a person, organization, object or machine through 2 steps as described in the function XXX. Trust is here transferred to the issuers of claims.

The most important functions to verify an identity are: `XXX`

The most important functions to manage an identity are: `XXX`


## Definitions

- `keys`: Keys are public keys from either external accounts, or contracts' addresses.
- `claim issuer`: is another smart contract or external account, which issues claims about this identity. The claim issuer can be an identity contract itself.
- `claim`: For details about claims see [#ERC735](https://github.com/ethereum/EIPs/issues/735)



## Specification


### Key Management

Keys are cryptographic public keys, or contract addresses associated with this identity.
The structure should be as follows:

- `key`: A public key owned by this identity
    - `purpose`: `uint256` The key purpose. e.g.,  1 = MANAGEMENT, 2 = ACTION, 3 = CLAIM, 4 = ENCRYPTION
    - `keyType`: The type of key used, which would be a `uint256` for different key types. e.g. 1 = ECDSA, 2 = RSA, etc.
    - `key`: `bytes32` The public key. // for non-hex and long keys, its the Keccak256 hash of the key 


```js
struct Key {
    uint256 purpose;
    uint256 keyType;
    bytes32 key;
}
```

#### getKey

Returns the full key data, if present in the identity.

``` js
function getKey(bytes32 _key) constant returns(uint256 purpose, uint256 keyType, bytes32 key);
```

#### keyHasPurpose

Returns `TRUE` if a key is present and has the given purpose. If the key is not present it returns `FALSE`.

``` js
function keyHasPurpose(bytes32 _key, uint256 purpose) constant returns(bool exists);
```


#### getKeysByPurpose

Returns an array of public key bytes32 held by this identity.

``` js
function getKeysByPurpose(uint256 _purpose) constant returns(bytes32[] keys);
```


#### addKey

Adds a `_key` to the identity. The `_purpose` specifies the purpose of the key. Initially, we propose four purposes:

- `1`: MANAGEMENT keys, which can manage the identity
- `2`: ACTION keys, which perform actions in this identity's name (signing, logins, transactions, etc.)
- `3`: CLAIM signer keys, used to sign claims on other identities which need to be revocable.
- `4`: ENCRYPTION keys, used to encrypt data e.g. hold in claims.

MUST only be done by keys of purpose `1`, or the identity itself. If it's the identity itself, the approval process will determine its approval.

**Triggers Event:** [KeyAdded](#keyadded)

``` js
function addKey(bytes32 _key, uint256 _purpose, uint256 _keyType) returns (bool success)
```


#### removeKey

Removes `_key` from the identity.

MUST only be done by keys of purpose `1`, or the identity itself. If it's the identity itself, the approval process will determine its approval.

**Triggers Event:** [KeyRemoved](#keyremoved)

``` js
function removeKey(bytes32 _key, uint256 _purpose) returns (bool success)
```


--------------------------------------------------------

### Identity usage


#### execute

Executes an action on other contracts, or itself, or a transfer of ether.
SHOULD require `approve` to be called with one or more keys of purpose `1` or `2` to approve this execution.

Execute COULD be used as the only accessor for `addKey`, `removeKey` and `replaceKey` and `removeClaim`.

**Returns `executionId`:** SHOULD be sent to the `approve` function, to approve or reject this execution.

**Triggers Event:** [ExecutionRequested](#executionrequested)
**Triggers on direct execution Event:** [Executed](#executed)

``` js
function execute(address _to, uint256 _value, bytes _data) returns (uint256 executionId)
```


#### approve

Approves an execution or claim addition.
This SHOULD require `n` of `m` approvals of keys purpose `1`, if the `_to` of the execution is the identity contract itself, to successfully approve an execution.
And COULD require `n` of `m` approvals of keys purpose `2`, if the `_to` of the execution is another contract, to successfully approve an execution.

**Triggers Event:** [Approved](#approved)
**Triggers on successfull execution Event:** [Executed](#executed)
**Triggers on successfull claim addition Event:** [ClaimAdded](#claimadded)

``` js
function approve(uint256 _id, bool _approve) returns (bool success)
```


--------------------------------------------------------


### Identity verification

Requires: [ERC 735](https://github.com/ethereum/EIPs/issues/735)

##### The following changes to [ERC 735](https://github.com/ethereum/EIPs/issues/735) are REQUIRED:

#### addClaim

This SHOULD create a pending claim, which SHOULD be approved or rejected by `n` of `m` `approve` calls from keys of purpose `1`.

Only Events:
**Triggers if the claim is new Event and approval process exists:** [ClaimRequested](#claimrequested)
**Triggers if the claim index existed Event:** [ClaimChanged](https://github.com/ethereum/EIPs/issues/735)


#### removeClaim

MUST only be done by the `issuer` of the claim, or keys of purpose `1`, or the identity itself. If it's the identity itself, the approval process will determine its approval.


--------------------------------------------------------


### Events


#### KeyAdded

MUST be triggered when `addKey` was successfully called.

``` js
event KeyAdded(bytes32 indexed key, uint256 indexed purpose, uint256 indexed keyType)
```


#### KeyRemoved

MUST be triggered when `removeKey` was successfully called.

``` js
event KeyRemoved(bytes32 indexed key, uint256 indexed purpose, uint256 indexed keyType)
```



#### ExecutionRequested

MUST be triggered when `execute` was successfully called.

``` js
event ExecutionRequested(uint256 indexed executionId, address indexed to, uint256 indexed value, bytes data)
```


#### Executed

MUST be triggered when `approve` was called and the execution was successfully approved.

``` js
event Executed(uint256 indexed executionId, address indexed to, uint256 indexed value, bytes data)
```


#### Approved

MUST be triggered when `approve` was successfully called.

``` js
event Approved(uint256 indexed executionId, bool approved)
```

##### The following changes to [ERC 735](https://github.com/ethereum/EIPs/issues/735) are REQUIRED:

#### ClaimRequested

MUST be triggered when `addClaim` was successfully called.


#### ClaimAdded

MUST be triggered when `approve` was called and the claim was successfully added.


## Constraints

- A claim can only be one type per type per issuer.



## Rationale
This specification was chosen to allow most flexibility and experimentation around identity. By having each identity in a separate contract it allows for cross identity compatibility, but at the same time extra and altered functionality for new use cases.

The main critic of this standard is the verification where each identity that issues a claim, also should have a separate CLAIM signing key attached. While [#ERC780](https://github.com/ethereum/EIPs/issues/780) uses a standardized registry to assign claims to addresses.
Both systems could work in conjunction and should be explored.
While also off-chain claims using DID verifiable claims and merkle tries can be added as claims and should be explored.

The rationale of this standard is to function as an open and very flexible container for identity.


## Implementation

- [DID resolver specification](https://github.com/WebOfTrustInfo/rebooting-the-web-of-trust-spring2018/blob/master/topics-and-advance-readings/DID-Method-erc725.md)
- [Implementation by mirceapasoi](https://github.com/mirceapasoi/erc725-735)
- [Implementation by Nick Poulden](https://github.com/OriginProtocol/identity-playground), interface at: https://erc725.originprotocol.com/


### Solidity Interface
```js
pragma solidity ^0.4.18;

contract ERC725 {

    uint256 constant MANAGEMENT_KEY = 1;
    uint256 constant ACTION_KEY = 2;
    uint256 constant CLAIM_SIGNER_KEY = 3;
    uint256 constant ENCRYPTION_KEY = 4;

    event KeyAdded(bytes32 indexed key, uint256 indexed purpose, uint256 indexed keyType);
    event KeyRemoved(bytes32 indexed key, uint256 indexed purpose, uint256 indexed keyType);
    event ExecutionRequested(uint256 indexed executionId, address indexed to, uint256 indexed value, bytes data);
    event Executed(uint256 indexed executionId, address indexed to, uint256 indexed value, bytes data);
    event Approved(uint256 indexed executionId, bool approved);

    struct Key {
        uint256 purpose; //e.g., MANAGEMENT_KEY = 1, ACTION_KEY = 2, etc.
        uint256 keyType; // e.g. 1 = ECDSA, 2 = RSA, etc.
        bytes32 key;
    }

    function getKey(bytes32 _key) public constant returns(uint256 purpose, uint256 keyType, bytes32 key);
    function keyHasPurpose(bytes32 _key, uint256 _purpose) public constant returns (bool exists);
    function getKeysByPurpose(uint256 _purpose) public constant returns (bytes32[] keys);
    function addKey(bytes32 _key, uint256 _purpose, uint256 _keyType) public returns (bool success);
    function removeKey(bytes32 _key, uint256 _purpose) public returns (bool success);
    function execute(address _to, uint256 _value, bytes _data) public returns (uint256 executionId);
    function approve(uint256 _id, bool _approve) public returns (bool success);
}
```

## Additional References

- [Slides of the ERC Identity presentation](https://www.slideshare.net/FabianVogelsteller/erc-725-identity)
- [In-contract claim VS claim registry](https://github.com/ethereum/wiki/wiki/ERC-735:-Claim-Holder-Registry-vs.-in-contract)
- [Identity related reports](https://www.weboftrust.info/specs.html)
- [W3C Verifiable Claims Use Cases](https://w3c.github.io/vc-use-cases/)
- [Decentralised Identity Foundation](https://identity.foundation)
- [Sovrin Foundation Self Sovereign Identity](https://sovrin.org/wp-content/uploads/2017/06/The-Inevitable-Rise-of-Self-Sovereign-Identity.pdf)

## Copyright
Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).