# Validator

## Get latest data requests <a href="#op-get-data-requests" id="op-get-data-requests"></a>

`GET /data-requests`

### Description

Retrieve the latest block headers. If at least one data request is present in a block, the block data is also returned. The notion of "latest" is determined by the query parameter `oldBlockHeight` and the ledger's current height. Validators use this endpoint to get the latest relevant blocks, extract the data requests in them, and respond to the data requests accordingly.

Using the block data, one can compute the data hash and verify consistency of the block header. In addition, using the block headers, one can verify the blocks are chained.

### Parameters

| Name           | In    | Type    | Required | Description                                          |
| -------------- | ----- | ------- | -------- | ---------------------------------------------------- |
| oldBlockHeight | query | integer | true     | Number of blocks the validator has already processed |

**Example**

`GET /data-requests?oldBlockHeight=1`

### Responses

| Status | Meaning                                                         | Description                   | Schema                              |
| ------ | --------------------------------------------------------------- | ----------------------------- | ----------------------------------- |
| 200    | [OK](https://tools.ietf.org/html/rfc7231#section-6.3.1)         | Succeeded                     | Inline                              |
| 400    | Bad Request                                                     | Request is invalid            | [ApiResponse](#schema-api-response) |
| 401    | [Unauthorized](https://tools.ietf.org/html/rfc7235#section-3.1) | API key is missing or invalid | [ApiResponse](#schema-api-response) |

#### 200 OK

Successfully retrieved the blocks and block data which contain data requests.

**Schema**

| Name   | Type                                                              | Required | Restrictions | Description |
| ------ | ----------------------------------------------------------------- | -------- | ------------ | ----------- |
| ok     | boolean                                                           | true     | none         | none        |
| blocks | dict<[BlockNumber](#schema-block-number), [Block](#schema-block)> | true     | none         | none        |

**Example**

```json
{
    "ok": true,
    "blocks": {
        "1": {
            "header": {
                "number": "1",
                "previousHash": "0ede53fd38d632f3a7d849f8ba8f70c851d772b53cecbc9d858fe7c8af03a858",
                "dataHash": "ee967360a911deb8f6bd77cbb49b334e1837c006c9b6cb2d59d8acd41964a6ac",
            },
        },
        "2": {
            "header": {
                "number": "2",
                "previousHash": "78aecc3976f7b2151ce0574278f816b8e5983e18229fde7b6e7c3ebdf5147baf",
                "dataHash": "3ec339eae416289f4ddd7dc2b69e8edf12ac013089207732ad6156e02dc21fb5",
            },
            "data": {
                "data": ["datum1==", "datum2=="],
            },
        },
    },
}
```

#### 400 Bad Request

Request is malformed. Make sure:

* `oldBlockHeight` is present in query parameter
* `oldBlockHeight` is a non-negative number
* `oldBlockHeight` is an integer
* `oldBlockHeight` is valid - no larger than the current block height of the ledger

**Example 1**

```json
{
    "ok": false,
    "message": "query.oldBlockHeight must be a non-negative integer",
}
```

**Example 2**

```json
{
    "ok": false,
    "message": "Invalid valid at query.oldBlockHeight. Expected: <=5; given: 10",
}
```

#### 401 Unauthorized

API key is missing or incorrect.

**Example**

```json
{
    "ok": false,
    "message": "Unauthorized",
}
```

## Get hashed trustee shares in an `Encryption` <a href="#op-get-hashed-trustee-shares" id="op-get-hashed-trustee-shares"></a>

`GET /encryptions/{token-hash}/hashed-trustee-shares`

### Description

Retrieves all the hashed trustee share from an `Encryption`. After receiving a new data request, before the validator attempt to respond to it, it should check if the threshold number of trustees have correctly responded to the data request. It can do this by checking consistent the shares and their hashes uploaded by the encryptor at encryption time. The former are the return values of this endpoint.

### Parameters

| Name       | In   | Type                     | Required | Description             |
| ---------- | ---- | ------------------------ | -------- | ----------------------- |
| token-hash | path | [Sha256](#schema-sha256) | true     | Hash value of the token |

**Example**

`GET /encryptions/d033713dd14552c060c55746afdb989cfee8e624ae94a932d79fd25630f728a4/hashed-trustee-shares`

### Responses

| Status | Meaning                                                         | Description                   | Schema                              |
| ------ | --------------------------------------------------------------- | ----------------------------- | ----------------------------------- |
| 200    | [OK](https://tools.ietf.org/html/rfc7231#section-6.3.1)         | Succeeded                     | Inline                              |
| 401    | [Unauthorized](https://tools.ietf.org/html/rfc7235#section-3.1) | API key is missing or invalid | [ApiResponse](#schema-api-response) |
| 404    | Not Found                                                       | Encryption not found          | [ApiResponse](#schema-api-response) |

#### 200 OK

Successfully retrieved the hashed trustee shares.

**Schema**

| Name               | Type                                                            | Required | Description                                     |
| ------------------ | --------------------------------------------------------------- | -------- | ----------------------------------------------- |
| ok                 | boolean                                                         | true     | none                                            |
| hashedTrusteeShare | dict<[TrusteeId](#schema-trustee-id), [Sha256](#schema-sha256)> | true     | A mapping from a trustee ID to its hashed share |

**Example**

```json
{
  "ok": true,
  "hashedTrusteeShare": {
      "trustee1": "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824",
      "my_trustee-2": "486ea46224d1bb4fb680f34f7c9ad96a8f24ec88be73ea8e5a6c65260e9cb8a7",
  },
}
```

#### 401 Unauthorized

API key is missing or incorrect.

**Example**

```json
{
    "ok": false,
    "message": "Unauthorized",
}
```

#### 404 Not Found

The encryption does not exist.

**Example**

```json
{
    "ok": false,
    "message": "Encryption with token hash d033713dd14552c060c55746afdb989cfee8e624ae94a932d79fd25630f728a4 not found",
}
```

## Get encrypted validator share in an `Encryption` <a href="#op-get-encrypted-validator-share" id="op-get-encrypted-validator-share"></a>

`GET /encryptions/{token-hash}/encrypted-validator-shares/{validator-id}`

### Description

Retrieves an encrypted validator share from an `Encryption`. After receiving a new data request, a validator should use this endpoint to get its encrypted share from the corresponding `Encryption`, decrypt it with its decryption key, then post the result with [postValidatorResponse](#opPostValidatorResponse).

### Parameters

| Name         | In   | Type                                | Required | Description             |
| ------------ | ---- | ----------------------------------- | -------- | ----------------------- |
| token-hash   | path | [Sha256](#schema-sha256)            | true     | Hash value of the token |
| validator-id | path | [ValidatorId](#schema-validator-id) | true     | The validator's ID      |

**Example**

`GET /encryptions/d033713dd14552c060c55746afdb989cfee8e624ae94a932d79fd25630f728a4/encrypted-validator-shares/validator1`

### Responses

| Status | Meaning                                                         | Description                   | Schema                              |
| ------ | --------------------------------------------------------------- | ----------------------------- | ----------------------------------- |
| 200    | [OK](https://tools.ietf.org/html/rfc7231#section-6.3.1)         | Succeeded                     | Inline                              |
| 400    | Bad Request                                                     | Request is invalid            | [ApiResponse](#schema-api-response) |
| 401    | [Unauthorized](https://tools.ietf.org/html/rfc7235#section-3.1) | API key is missing or invalid | [ApiResponse](#schema-api-response) |
| 404    | Not Found                                                       | Encryption not found          | [ApiResponse](#schema-api-response) |

#### 200 OK

Successfully retrieved the encrypted validator share.

**Schema**

| Name                    | Type                     | Required | Description                   |
| ----------------------- | ------------------------ | -------- | ----------------------------- |
| ok                      | boolean                  | true     | none                          |
| encryptedValidatorShare | [Base64](#schema-base64) | true     | The encrypted validator share |

**Example**

```json
{
  "ok": true,
  "encryptedValidatorShare": "base64_encoded_data"
}
```

#### 400 Bad Request

Validator does not exist or does not reference this PAD instance.

**Example**

```json
{
    "ok": false,
    "message": "Validator with ID validator1 does not exist in the PAD instance",
}
```

#### 401 Unauthorized

API key is missing or incorrect.

**Example**

```json
{
    "ok": false,
    "message": "Unauthorized",
}
```

#### 404 Not Found

The encryption does not exist.

**Example**

```json
{
    "ok": false,
    "message": "Encryption with token hash d033713dd14552c060c55746afdb989cfee8e624ae94a932d79fd25630f728a4 not found",
}
```

## Post validator response <a href="#op-post-validator-response" id="op-post-validator-response"></a>

`POST /data-requests/{token}/validator-responses`

### Description

Posts a validator response to the ledger.

After retrieving and finish decrypting its share, the validator needs to post the result back to the ledger so that eventually, the decryptor can decrypt a secret. The validator shares combining also reveals the identity of the decryptor.

### Parameters

| Name  | In   | Type                                                         | Required | Description                                                                            |
| ----- | ---- | ------------------------------------------------------------ | -------- | -------------------------------------------------------------------------------------- |
| token | path | [Token](#schema-token)                                       | true     | ID of the data request                                                                 |
| -     | body | [SignedValidatorResponse](#schema-signed-validator-response) | true     | The decrypted share, along with a digital signature of the validator and some metadata |

**Example**

`POST /data-requests/e3b0c44298fc1c149afbf4c8996fb924/validator-responses`

```json
{
  "validatorResponse": "{\"padName\":\"my-pad-1.0\",\"token\":\"e3b0c44298fc1c149afbf4c8996fb924\",\"validatorShare\":\"0110\",\"type\":\"validator_response\",\"validatorId\":\"validator1\"}",
  "signature": {
    "signerMetadata": {
      "id": "validator1",
      "fullName": "Validator-1",
      "role": "Validator"
    },
    "payload": "MEQCIDbFV8FH8ZTbM0wrKPHSk0lrkiIFsP3/GcU4htiGc6XOAiBOqJZgbeUKxPXgIOZGek6ryoJ+jhmwbcJh0+mSHsSiTQ=="
  }
}
```

### Responses

| Status | Meaning                                                         | Description                                        | Schema                              |
| ------ | --------------------------------------------------------------- | -------------------------------------------------- | ----------------------------------- |
| 200    | [OK](https://tools.ietf.org/html/rfc7231#section-6.3.1)         | Succeeded                                          | [ApiResponse](#schema-api-response) |
| 400    | Bad Request                                                     | Data request and trustee response are inconsistent | [ApiResponse](#schema-api-response) |
| 401    | [Unauthorized](https://tools.ietf.org/html/rfc7235#section-3.1) | API key is missing or invalid                      | [ApiResponse](#schema-api-response) |
| 403    | Forbidden                                                       | Trustee is not in the instance                     | [ApiResponse](#schema-api-response) |
| 404    | Not found                                                       | Data request not found                             | [ApiResponse](#schema-api-response) |
| 409    | Conflict                                                        | Response has been made before                      | [ApiResponse](#schema-api-response) |

#### 200 OK

Validator response is successfully post.

**Example**

```json
{
    "ok": true,
    "message": "Successfully posted validator response",
}
```

#### 400 Bad request

Request is invalid. Make sure that :

* `padName` in `ValidatorResponse` is consistent with the PAD instance to which the API key is pointing
* `token` in path and `ValidatorResponse` are consistent
* `validatorId` in `ValidatorResponse` and `signature` are consistent
* `role` is `Validator` in `signature`
* signature in `signature` is consistent with the payload `ValidatorResponse`

**Example 1**

```json
{
    "ok": false,
    "message": "Inconsistent validator ID",
}
```

**example 2**

```json
{
    "ok": false,
    "message": "Inconsistent PAD instance name",
}
```

**example 3**

```json
{
    "ok": false,
    "message": "Invalid signature",
}
```

#### 401 Unauthorized

Api key is missing or invalid.

**Example**

```json
{
    "ok": false,
    "message": "Unauthorized",
}
```

#### 403 Forbidden

The validator is not part of the instance. Recall that the list of validators is determined by the *Operator* at instance creation time.

**Example**

```json
{
    "ok": false,
    "message": "Not a validator of the instance",
}
```

#### 404 Not Found

The server cannot find a data request pointed by the token in the path parameter.

**Example**

```json
{
    "ok": false,
    "message": "Data request not found",
}
```

#### 409 Conflict

A response from the same validator has been made for the same data request before.

**Example**

```json
{
    "ok": false,
    "message": "Validator response has been made for this request",
}
```

## Schemas

### ApiResponse <a href="#schema-api-response" id="schema-api-response"></a>

**Example**

```json
{
  "ok": true,
  "message": "string"
}
```

#### Schema

| Name    | Type    | Required | Description                      |
| ------- | ------- | -------- | -------------------------------- |
| ok      | boolean | true     | The request is successful or not |
| message | string  | true     | none                             |

### BlockNumber <a href="#schema-block-number" id="schema-block-number"></a>

ID of a block. It is an incremental index starting from 0. For example, if a ledger has height 10, then it has blocks 0, 1, ..., 9. The next block has block number 10.

#### Schema

| Type    | Restrictions |
| ------- | ------------ |
| integer | Non-negative |

### Block <a href="#schema-block" id="schema-block"></a>

Blocks are put sequentially as a blockchain to form a ledger. It consists of the header (which contains the chaining information) and optionally the data (from which data requests and trustee and validator responses can be extracted).

**Example 1**

```json
{
    "header": {
        "number": "1",
        "previousHash": "0ede53fd38d632f3a7d849f8ba8f70c851d772b53cecbc9d858fe7c8af03a858",
        "dataHash": "ee967360a911deb8f6bd77cbb49b334e1837c006c9b6cb2d59d8acd41964a6ac",
    },
}
```

**Example 2**

```json
{
    "header": {
        "number": "2",
        "previousHash": "78aecc3976f7b2151ce0574278f816b8e5983e18229fde7b6e7c3ebdf5147baf",
        "dataHash": "3ec339eae416289f4ddd7dc2b69e8edf12ac013089207732ad6156e02dc21fb5",
    },
    "data": {
        "data": ["datum1==", "datum2=="],
    },
}
```

#### Schema

| Name   | Type                                | Required | Description |
| ------ | ----------------------------------- | -------- | ----------- |
| header | [BlockHeader](#schema-block-header) | true     | none        |
| data   | [BlockData](#schema-block-data)     | false    | none        |

### BlockHeader <a href="#schema-block-header" id="schema-block-header"></a>

Block header contains metadata of a block. They are sufficient to prove the blocks form a chain without the need of block data, because the `previousHash` field in the schema refers to the hash of the previous block header, instead of the entire previous block. Thus, if the block data is irrelevant (for example not containing any data request when one is asking for them), it can be skipped.

If the block number is 0, the `number` and `previousHash` fields are empty. `dataHash` is computed with the same block's data. Refer to code samples on how to compute hash of a block header.

**Example 1**

```json
{
    "dataHash": "b24fd1a8c0c37f388f67ce6583710e3b1e5cfa79e652f764e92ee412299ac6c5",
}
```

**Example 2**

```json
{
    "number": "1",
    "previousHash": "0ede53fd38d632f3a7d849f8ba8f70c851d772b53cecbc9d858fe7c8af03a858",
    "dataHash": "ee967360a911deb8f6bd77cbb49b334e1837c006c9b6cb2d59d8acd41964a6ac",
}
```

#### Schema

| Name         | Type                                | Required | Description                         |
| ------------ | ----------------------------------- | -------- | ----------------------------------- |
| number       | [BlockNumber](#schema-block-number) | false    | Block number of the current block   |
| previousHash | [Sha256](#schema-sha256)            | false    | Hash of the previous block's header |
| dataHash     | [Sha256](#schema-sha256)            | true     | Hash of this block's data           |

### BlockData <a href="#schema-block-data" id="schema-block-data"></a>

Block data contains "transactions". In PAD, these are the data requests and trustee and validator responses. See code samples to see how block data are decoded.

**Example**

```json
{
    "data": ["datum1==", "datum2=="],
}
```

#### Schema

| Name | Type                            | Required | Description |
| ---- | ------------------------------- | -------- | ----------- |
| data | array<[Base64](#schema-base64)> | true     | none        |

### Base64

A base64-encoded binary data.

**Example**

```json
"aGVsbG8gd29ybGQ="
```

#### Schema

| Type   | Restrictions |
| ------ | ------------ |
| string | none         |

### Sha256

A Sha256 hash value as a hexidecimal string.

**Example**

```json
"d033713dd14552c060c55746afdb989cfee8e624ae94a932d79fd25630f728a4"
```

#### Schema

| Type   | Restrictions        |
| ------ | ------------------- |
| string | `/[0-9a-fA-F]{64}/` |

### TrusteeId <a href="#schema-trustee-id" id="schema-trustee-id"></a>

ID of a trustee. It contains only alphanumerical characters, underscores (\_) and dashes (-). It has length inclusively between 3 and 30.

**Example**

```
trustee1
```

#### Schema

| Type   | Restrictions          |
| ------ | --------------------- |
| string | `[a-zA-Z0-9-_]{3,30}` |

### ValidatorId <a href="#schema-validator-id" id="schema-validator-id"></a>

ID of a validator. It contains only alphanumerical characters, underscores (\_) and dashes (-). It has length inclusively between 3 and 30.

**Example**

```
validator1
```

#### Schema

| Type   | Restrictions          |
| ------ | --------------------- |
| string | `[a-zA-Z0-9-_]{3,30}` |

### Token <a href="#schema-token" id="schema-token"></a>

A 128-bit random string kept secret between the encryptor and decryptor after encryption stage and before data request stage. It identifies a data request. Its hash value identifies an `encryption`. The decryptor posts it on the ledger at data request stage.

**Example**

```
"0fe5ff17c6ee6efa8ca385587b1e1ac2"
```

#### Schema

| Type   | Restrictions        |
| ------ | ------------------- |
| string | `/[0-9a-fA-Z]{32}/` |

### PadName <a href="#schema-pad-name" id="schema-pad-name"></a>

ID of a PAD instance. Its length must be inclusively between 4 and 30. It should contains only lowercase letters, digits, periods (`.`) or dashes (`-`). It must start with a lowercase letter.

It is seldom used as a request parameter because the API key in the request already identifies a PAD instance.

**Example**

```json
"my-pad-1.0"
```

#### Schema

| Type   | Restrictions              |
| ------ | ------------------------- |
| string | `/[a-z][a-z0-9.-]{3,29}/` |

### ValidatorResponse <a href="#schema-validator-response" id="schema-validator-response"></a>

A validator response to a data request. It contains the decrypted validator share for the decryptor to perform a full decryption on a secret. It also consists of metadata for identifying the corresponding data request.

**Example**

```json
{
    "padName": "my-pad-1.0",
    "token": "e3b0c44298fc1c149afbf4c8996fb924",
    "validatorShare": "0110",
    "type": "validator_response",
    "validatorId": "validator1",
}
```

#### Schema

| Name           | Type                                | Required | Restrictions | Description                                   |
| -------------- | ----------------------------------- | -------- | ------------ | --------------------------------------------- |
| padName        | [PadName](#schema-pad-name)         | true     | none         | The instance where the data request is posted |
| token          | [Token](#schema-token)              | true     | none         | The ID of the data request                    |
| validatorShare | [Base64](#schema-base64)            | true     | none         | The decrypted validator share                 |
| type           | enum                                | true     | none         | Type of response                              |
| validatorId    | [ValidatorId](#schema-validator-id) | true     | none         | ID of the responding validator                |

#### Enumerated Values

| Property | Value                  |
| -------- | ---------------------- |
| type     | `"validator_response"` |

### SignedValidatorResponse <a href="#schema-signed-validator-response" id="schema-signed-validator-response"></a>

A validator response attached with a digital signature for everyone to validate the response's integrity.

Note that the validator response is represented as a string (instead of an object). This ensures that there is a unified way to verify the signature.

**Example**

```json
{
  "validatorResponse": "{\"padName\":\"my-pad-1.0\",\"token\":\"e3b0c44298fc1c149afbf4c8996fb924\",\"validatorShare\":\"0110\",\"type\":\"validator_response\",\"validatorId\":\"validator1\"}",
  "signature": {
    "signerMetadata": {
      "id": "validator1",
      "fullName": "Validator-1",
      "role": "Validator"
    },
    "payload": "MEQCIDbFV8FH8ZTbM0wrKPHSk0lrkiIFsP3/GcU4htiGc6XOAiBOqJZgbeUKxPXgIOZGek6ryoJ+jhmwbcJh0+mSHsSiTQ=="
  }
}
```

### Schema

| Name              | Type                                                    | Required | Description |
| ----------------- | ------------------------------------------------------- | -------- | ----------- |
| validatorResponse | string<[ValidatorResponse](#schema-validator-response)> | true     | none        |
| signature         | [Signature](#schema-signature)                          | true     | none        |

### Participant <a href="#schema-participant" id="schema-participant"></a>

Metadata of a participant in PAD. It can currently be used to describe a trustee or a validator.

**Example**

```json
{
  "id": "validator1",
  "fullName": "Validator-1",
  "role": "Validator"
}
```

#### Schema

| Name     | Type                                                                   | Required | Description                                              |
| -------- | ---------------------------------------------------------------------- | -------- | -------------------------------------------------------- |
| id       | [TrusteeId](#schema-trustee-id) or [ValidatorId](#schema-validator-id) | true     | `/[0-9a-zA-Z-_]{3,30}/`                                  |
| fullName | string                                                                 | true     | `/Trustee-[0-9a-zA-Z_]+/` or `/Validator-[0-9a-zA-Z_]+/` |
| role     | enum                                                                   | true     | none                                                     |

#### Enumerated Values

| Property | Value     |
| -------- | --------- |
| role     | Trustee   |
| role     | Validator |
| role     | Server    |

### Signature <a href="#schema-signature" id="schema-signature"></a>

A digital signature. It consists of the metadata of the signer, including its ID, and the signature payload encoded in base64.

**Schema**

```json
{
  "signerMetadata": {
    "id": "string",
    "fullName": "string",
    "role": "Trustee",
  },
  "payload": "MEQCIDbFV8FH8ZTbM0wrKPHSk0lrkiIFsP3/GcU4htiGc6XOAiBOqJZgbeUKxPXgIOZGek6ryoJ+jhmwbcJh0+mSHsSiTQ==",
}
```

#### Schema

| Name           | Type                              | Required | Description |
| -------------- | --------------------------------- | -------- | ----------- |
| signerMetadata | [Participant](#schemaparticipant) | false    | none        |
| payload        | [Base64](#schema-base64)          | false    | none        |