> For the complete documentation index, see [llms.txt](https://unirep.gitbook.io/unirep/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://unirep.gitbook.io/unirep/protocol/glossary/reputation.md).

# Reputation

Definition of reputation in UniRep

## Reputation

* The reputation in UniRep protocol includes
  * `posRep`: is the positive reputation given by the attester
  * `negRep`: is the negative reputation given by the attester
  * `graffiti`: is the message given by the attester
  * `signUp`: indicates if the attester authenticates the user
* The hash of the reputation is computed by the [Poseidon hash](https://www.poseidon-hash.info/) function.

```typescript
const hashReputation = hash(posRep, negRep, graffiti, signUp)
```

* The overall **reputation status** of a user is stored in the user's [User State Tree](/unirep/protocol/glossary/trees.md#user-state-tree)
  * where the index of the leaf is the attester ID
  * the leaf value is the accumulated `hashReputation` that the attester gives

## Attestation

* The attestation is almost the same as reputation, but it includes an `attesterId`
* The hash of attestation is computed by

```typescript
const hashAttestation = hash(attesterId, posRep, negRep, graffiti, signUp)
```

* The attestations to an epoch key would be chained together. A hashchain would be formed by the hashes of the attestations.

  * For example, **Hash chain** is computed by

  ```
  const hashChainResult = hash(hashAttestation_3, hash(hashAttestation_2, hash(hashAttestation_1, 0)))
  ```

  * So user **can not omit any attestation** because the [circuit](/unirep/protocol/circuits/user-state-transition-proof.md) requires each attestation in the hashchain to be processed. <mark style="color:red;">**->**</mark> <mark style="color:red;">**Non-repudiable**</mark>
  * if user omits an attestation, then the computed hashchain would not match the one in the Unirep contract

{% hint style="info" %}
See also

* [Trees](/unirep/protocol/glossary/trees.md)
* [Epoch Transition](/unirep/protocol/glossary/epoch-transition.md)
* [User State Transition](/unirep/protocol/glossary/user-state-transition.md)
* [User State Transition Proof](/unirep/protocol/circuits/user-state-transition-proof.md)
  {% endhint %}