# Consensus

## FP - Finalization Proof

Signature by some quorum member (validator) that told:

> I agree to vote for block <mark style="color:red;">**B**</mark> with index <mark style="color:green;">**I**</mark> and hash <mark style="color:purple;">**H**</mark> created by shard leader <mark style="color:orange;">**L**</mark>. The previous block hash was <mark style="color:blue;">**P**</mark>

On a more technical level - the validator that is part of the current quorum when receiving a block proposal from the shard leader generates a signature:

```javascript
import {crypto} from 'web1337';

let prevBlockHash = "b5d6a3736a146fe921e40be95b8e41a0f953a20aedb740769440be4b53795ff7";

let blockID = "0:9GQ46rqY238rk2neSwgidap9ww5zbAN4dyqyC7j5ZnBK:1618";

let blockHash = "36514c7acfd77950b23baced61f70bd7126f5dac4bc7f2eb110f364123901c42";

// Epoch Full ID = epoch.hash+"#"+epoch.index
// Just concat hash + # + index
let epochFullID = "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef#0";

let dataThatShouldBeSigned = prevBlockHash+blockID+blockHash+epochFullID;


// Imagine that validator holds it locally
let quorumValidatorPrivateKey = "MC4CAQAwBQYDK2VwBCIEILdhTMVYFz2GP8+uKUA+1FnZTEdN8eHFzbb8400cpEU9";


let finalizationProof = await crypto.ed25519.signEd25519(dataThatShouldBeSigned,quorumValidatorPrivateKey);
```

After quorum member generate this signature - it can be handled(by someone - since it proof is public) and aggregated to get the **AFP - aggregated finalization proof**

## AFP - Aggregated Finalization Proof

Aggregation of 2/3N of FPs gives us AFP. This is how it looks like:

```json
{
    "prevBlockHash": "b5d6a3736a146fe921e40be95b8e41a0f953a20aedb740769440be4b53795ff7",
    "blockID": "0:9GQ46rqY238rk2neSwgidap9ww5zbAN4dyqyC7j5ZnBK:1618",
    "blockHash": "36514c7acfd77950b23baced61f70bd7126f5dac4bc7f2eb110f364123901c42",
    "proofs": {
        "9GQ46rqY238rk2neSwgidap9ww5zbAN4dyqyC7j5ZnBK": "0pOSDm2Zr615gDociLowbGD3IU3eXZKqXOpGchHx8pQEBFThgKzRE2Qt+jTw4ikKJruVCMlDHjwaFOJuufJSAA==",
        "6XvZpuCDjdvSuot3eLr24C1wqzcf2w4QqeDh9BnDKsNE": "msSzIiJ9R7x+U+aLUYWyJVF2ylB8qQmel0U7XHPSRXlRZtc+AJVGctXiDZ89K54xpWL+E9TqDmj9H2Cqvz+MAg=="
    }
}
```

In our explorer you can check the AFP on the block page - look at the link next to the status

<figure><img src="https://3015034387-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FNKK8Y1uEALYsObbKnPLt%2Fuploads%2FNkLGxCSCdjxC1SO2BYyl%2Fimage.png?alt=media&#x26;token=86f99208-a385-4b3b-a87a-62b3d28ddd4c" alt=""><figcaption></figcaption></figure>

Clicking on the link will show you the raw version of AFP:

<figure><img src="https://3015034387-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FNKK8Y1uEALYsObbKnPLt%2Fuploads%2FBMEPJcvb1r2koTfegC1K%2Fimage.png?alt=media&#x26;token=cbf3f2e5-2264-49f1-aca5-cf485cba0062" alt=""><figcaption></figcaption></figure>

Probably the most interesting field here is `proofs` - these are just the FP's from the validators that are part of the quorum of the epoch when the block was generated.

You can verify it yourself using this code:

```javascript
import {crypto} from 'web1337';

let prevBlockHash = "b5d6a3736a146fe921e40be95b8e41a0f953a20aedb740769440be4b53795ff7";

let blockID = "0:9GQ46rqY238rk2neSwgidap9ww5zbAN4dyqyC7j5ZnBK:1618";

let blockHash = "36514c7acfd77950b23baced61f70bd7126f5dac4bc7f2eb110f364123901c42";

// Epoch Full ID = epoch.hash+"#"+epoch.index
// Just concat hash + # + index
let epochFullID = "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef#0";

let dataThatShouldBeSigned = prevBlockHash+blockID+blockHash+epochFullID;

// Let verify FP for quorum member 9GQ46rqY238rk2neSwgidap9ww5zbAN4dyqyC7j5ZnBK

let quorumMember = "9GQ46rqY238rk2neSwgidap9ww5zbAN4dyqyC7j5ZnBK";
let fpProof = "0pOSDm2Zr615gDociLowbGD3IU3eXZKqXOpGchHx8pQEBFThgKzRE2Qt+jTw4ikKJruVCMlDHjwaFOJuufJSAA==";


let isFinalizationProofOk = await crypto.ed25519.verifyEd25519(dataThatShouldBeSigned,fpProof, quorumMember);

// In case 2/3N+1 of quorum created valid FPs - then this AFP is valid
```

Sometimes, another case is also possible:

<figure><img src="https://3015034387-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FNKK8Y1uEALYsObbKnPLt%2Fuploads%2FT8c3UOc91oHZ0rif4Yw4%2Fimage.png?alt=media&#x26;token=96ea7213-5e26-4c66-ac80-a9d73b30b0ea" alt=""><figcaption></figcaption></figure>

{% hint style="info" %}
If you see something like this in the explorer, it means that the network has finished the epoch on this block. This block is also valid and was included in the state, but indirectly - via the process of voting for ending of epoch. Such AFP is impossible to verify and it used just as a stub for user interface of explorer
{% endhint %}

## LRP - Leader Rotation Proof

Signature by some quorum member (validator) that told:

> I agree to finish FPs generation for shard leader <mark style="color:orange;">**L**</mark> on index <mark style="color:red;">**I**</mark> and hash <mark style="color:purple;">**H**</mark>. The hash of first block by this leader is <mark style="color:green;">**F**</mark>

## ALRP - Aggregated Leader Rotation Proof

Aggregation of 2/3N of LRPs gives us ALRP. This is how it looks like:

```json
{
    "firstBlockHash": "a2d375da65094d65d25cc449abd10dfcea6c1b011cd0ce190379ca09b82b842b",
    "skipIndex": 131,
    "skipHash": "fb963df17e1b7f437636e4c5c94b32d43b86049393bafdf01299a304511c59eb",
    "proofs": {
        "9GQ46rqY238rk2neSwgidap9ww5zbAN4dyqyC7j5ZnBK": "W4Otr1LGk5KVYYBp+10hi3n2l+iVyNc+BgLYh3Yi4JEGiBG+MlozqSk4RjWu638ccAkeaebk6IhgmNKu8R9zAw=="
    }
}
```

## EFP - Epoch Finalization Proof

Signature by some quorum member (validator) that told:

> I agree to finish epoch <mark style="color:red;">**X**</mark> on shard <mark style="color:purple;">**Y**</mark>. The last shard leader had index <mark style="color:green;">**Q**</mark> in leaders sequence. His last block has height **W** and hash <mark style="color:yellow;">**H**</mark>. His first block has hash <mark style="color:orange;">**F**</mark>

## AEFP - Aggregated Epoch Finalization Proof

Aggregation of 2/3N of EFPs gives us AEFP. This is how it looks like:

```json
{
  
    "lastLeader": 2,
    "lastIndex": 31,
    "lastHash": "ab963df17e1b7f437636e4c5c94b32d43b86049393bafdf01299a304511c59eb",
    "hashOfFirstBlockByLastLeader": "b2d375da65094d65d25cc449abd10dfcea6c1b011cd0ce190379ca09b82b842b",
    "proofs": {
        "9GQ46rqY238rk2neSwgidap9ww5zbAN4dyqyC7j5ZnBK": "W4Otr1LGk5KVYYBp+10hi3n2l+iVyNc+BgLYh3Yi4JEGiBG+MlozqSk4RjWu638ccAkeaebk6IhgmNKu8R9zAw=="
    }
}
```