# Census Service

The Census Service provides a service for both organizations and users. Its purpose is to store and manage census, which are a list of public keys stored as a Merkle Tree.

The organizer can:

  • Create a new census
  • Add new claims to a census (hash of the public key)
  • Export the list of claims
  • Recover the Merkle Root
  • Publish the census to IPFS or similar
  • Import a census from IPFS

A user can:

  • Request the Merkle Root
  • Given a claim, request the Merkle Proof (the siblings allowing to prove that the claim matches the current root hash)
  • Check if a Merkle Proof is valid

# JSON API

The Census API interactions follow the JSON API.

# Add Census

Private Method

When using censushttp only the root key administration can create new census if rootKey specified.

When using the gateway, only the public keys specified in --allowedAddrs can create new census and the address is added automatically as prefix for the censusId (to avoid colision and for security reasons).

{
  "id": "req-12345678",
  "request": {
    "method": "addCensus",
    "censusId": "<entropy-hash>", // Unique hex payload like the hash of the original census name
    "pubKeys": ["040012345...", "040123456...", "..."],  // hex pubKeys allowed to request private methods
    "timestamp": 1556110671
  },
  "signature": "hexString"
}
{
  "id": "req-12345678",
  "response": {
    "ok": true,
    "censusId": "0x12345678.../<entropy-hash>", // The full census ID that any client should use from now on
    "request": "req-12345678", // request ID here as well, to check its integrity
    "timestamp": 1556110672
  },
  "signature": "0x1234..."
}

# Add Claim

Private Method

Adds a payload to the census Merkle Tree and returns the updated Root Hash

  • If digested is false, the receiver will handle censusKey as a raw public key encoded in base64
    • The receiver should compute its Poseidon Hash and store it
  • If digested is true, the receiver will handle censusKey as an already hashed public key, encoded in base64
    • The receiver should store censusKey as it is
  • On weighted census, censusValue contains the amount of power that the given censusKey has
{
  "id": "req-12345678",
  "request": {
    "method": "addClaim",
    "censusId": "0x12345678/0x23456789", // where to add the claim (must already exist)
    "digested": false,  // is the key digested? the Gateway should do it if not
    "censusKey": "base64-string", // usually the public key in base64 or its hash, also in base64
    "censusValue": "base64-string", // usually the numeric weight (big num). Can be empty (for non-weighted census)
    "timestamp": 1556110671
  },
  "signature": "hexString"
}
{
  "id": "req-12345678",
  "response": {
    "ok": true,
    "root": "0x1234...",
    "request": "req-12345678", // request ID here as well, to check its integrity
    "timestamp": 1556110672
  },
  "signature": "0x1234..."
}

Used in:

# Add Claim Bulk

Private Method

Adds a set of payloads to the census Merkle Tree and returns the updated Root Hash

  • If digested is false, the receiver will handle censusKey as raw public keys encoded in base64
    • The receiver should compute their Poseidon Hashes and store them
  • If digested is true, the receiver will handle censusKey as already hashed public keys, encoded in base64
    • The receiver should store censusKeys as they are
  • If any of the claims could not be added, invalidClaims contains an array with the indexes that failed
{
  "id": "req-2345679",
  "request": {
    "method": "addClaimBulk",
    "censusId": "0x12345678/0x23456789", // where to add the claims (must already exist)
    "digested": false,  // are the keys digested? the Gateway should do it if not
    "censusKeys": [  // the public keys in base64 or their hashes, also in base64
        "base64-string-1",
        "base64-string-2",
        "base64-string-3"
    ],
    "censusValues": [  // can be empty (for non-weighted census)
        "base64-string-1",
        "base64-string-2",
        "base64-string-3"
],
    "timestamp": 1556110671
  },
  "signature": "hexString"
}
{
  "id": "req-2345679",
  "response": {
    "ok": true,
    "root": "0x1234...",
    "invalidClaims": [1, 2],   // string-1 and string-2 were not added
    "request": "req-2345679",
    "timestamp": 1556110672
  },
  "signature": "0x1234..."
}

# Get Root

Public Method

{
  "id": "req-12345678",
  "request": {
    "method": "getRoot",
    "censusId": "0x12345678/0x23456789",
  },
  "signature": ""  // Leave empty
}
{
  "id": "req-12345678",
  "response": {
    "root": "0x1234...", // the current census root hash
    "request": "req-2345679",
    "timestamp": 1556110672
  },
  "signature": "0x1234..."
}

# Get Size

Public Method

{
  "id": "req-12345678",
  "request": {
    "method": "getSize",
    "censusId": "0x12345678/0x23456789",
    "rootHash": "optional-hexString", // from a specific version
  },
  "signature": ""  // Leave empty
}
{
  "id": "req-12345678",
  "response": {
    "size": int64, // the current size of the census
    "request": "req-2345679",
    "timestamp": 1556110672
  },
  "signature": "0x1234..."
}

# Generate Proof

Public Method

{
  "id": "req-12345678",
  "request": {
    "method": "genProof",
    "censusId": "0x123456789", // Merkle Root of the census for which the claim siblings are requested
    "censusKey": "base64-string", // the leaf for which the proof is requested (base64 encoded)
    "censusValue": "hexString", // if weighted census, the hexadecimal representation of the numeric big num weight
    "digested": false,  // is the key digested? the backend should do it if not
    "rootHash": "optional-hexString" // from a specific version
  },
  "signature": ""  // Leave empty
}
{
  "id": "req-12345678",
  "response": {
    "siblings": "hexString",
    "request": "req-12345678",
    "timestamp": 1556110672
  },
  "signature": "0x1234..."
}

# Check Proof

Public Method

{
  "id": "req-12345678",
  "request": {
    "method": "checkProof",
    "censusId": "0x123456789", // Merkle Root of the census for which the Merkle Tree's claim will be checked
    "censusKey": "base64-string", // the leaf for which data is requested
    "censusValue": "hexString", // if weighted census, the hexadecimal representation of the weight big num
    "proofData": "hexString", // the siblings, same format obtained in genProof
    "digested": false,  // is the claim digested? the backend should do it if not
    "rootHash": "optional-hexString" // from a specific version
  },
  "signature": ""  // Leave empty
}
{
  "id": "req-12345678",
  "response": {
    "validProof": bool, // it's a valid proof or not
    "request": "req-12345678",
    "timestamp": 1556110672
  },
  "signature": "0x1234..."
}

# Census Dump

Dumps the entire content of the census as an array of hexStrings ready to be imported to another census service.

Private Method

{
  "id": "req-12345678",
  "request": {
    "method": "dump",
    "censusId": "0x12345678/0x23456789",
    "rootHash": "optional-hexString", // from a specific version
    "timestamp": 1556110671
  },
  "signature": "hexString"
}
{
  "id": "req-12345678",
  "response": {
    "censusDump": "base64-string", // the serialized, base64 encoded, census data (for using with import)
    "request": "req-12345678",
    "timestamp": 1556110672
  },
  "signature": "0x1234..."
}

# Census Dump Plain

Dumps the content of the census in base64 format. The dump cannot be used afterwars with importDump.

Private Method

{
  "id": "req-12345678",
  "request": {
    "method": "dumpPlain",
    "censusId": "0x12345678/0x23456789",
    "rootHash": "optional-hexString", // from a specific version
    "timestamp": 1556110671
  },
  "signature": "hexString"
}
{
  "id": "req-12345678",
  "response": {
    "censusKeys": [
        "base64-string",
        "base64-string",
        "base64-string"
    ],
    "censusValues": [ // can be empty if not weighted census
        "hexString-1",
        "hexString-2",
        "hexString-3",
    ]
    "request": "req-12345678",
    "timestamp": 1556110672
  },
  "signature": "0x1234..."
}

# Census Import Local Dump

Only works with specific merkle tree format used by dump method. To add a list of plain claims use addClaimBulk instead.

Private Method

{
  "id": "req-12345678",
  "request": {
    "method": "importDump",
    "censusId": "0x12345678/0x23456789", // the censusId where to import the data
    "censusDump": "base64-string", // serialized base64 encoded raw census data (generated with dump)
    "timestamp": 1556110671
  },
  "signature": "0x1234..."
}
{
  "id": "req-12345678",
  "response": {
    "request": "req-12345678",
    "timestamp": 1556110672
  },
  "signature": "0x1234..."
}

# Census Publish

Exports and publish the entire census on the storage of the backend (usually IPFS). Returns the URI.

Private Method

{
  "id": "req-12345678",
  "request": {
    "method": "publish",
    "censusId": "0x12345678/0x23456789",
    "rootHash": "optional-hexString", // the census snapshot to publish, if not specified, use the last one
    "timestamp": 1556110671
  },
  "signature": "hexString"
}
{
  "id": "req-12345678",
  "response": {
    "request": "req-12345678",
    "uri": "uri-string", // where to find the census, i.e ipfs://Qmasdf94341...
    "timestamp": 1556110672
  },
  "signature": "0x1234..."
}

# Census Import Remote

Import a previously published remote census. Only valid URIs accepted (depends on the backend).

Private Method

{
  "id": "req-12345678",
  "request": {
    "method": "importRemote",
    "censusId": "0x12345678/0x23456789",
    "uri": "uri-string", // where to find the remote census, i.e ipfs://Qmasdf94341...
    "timestamp": 1556110671
  },
  "signature": "hexString"
}
{
  "id": "req-12345678",
  "response": {
    "request": "req-12345678",
    "timestamp": 1556110672
  },
  "signature": "0x1234..."
}
Last Updated: 8/2/2021, 4:51:29 PM