# Symbiosis Relayer Node

## Introducing Relayer Node

A relayer node is a physical or virtual machine running the Symbiosis relayer software and registered in the Symbiosis PoS Staking Contracts. Only registered nodes are authorized to participate in the operations of the Symbiosis Relayers Network.

Relayer nodes are designed to coordinate with one another to execute cross-chain operations and to manage network activity in a decentralized manner.

{% hint style="info" %}
**Important:** Nodes running the relayer software but not registered or blocked in the PoS Staking Contracts are not considered part of the Relayers Network and cannot participate in relaying operations.
{% endhint %}

## Relayer Node Keys

Each relayer node operates with two types of cryptographic keys:

1. Relayer node's private key,
2. MPC key fragments.

### 1. Relayer Node’s Private Key

Every relayer node has its own unique private key, which is generated during the installation and setup of the relayer software. The corresponding address must be registered in the PoS Staking Contracts, and the key is used for:

* Authenticating the relayer node within the Relayers Network.
* Signing transactions related to epoch changes.

If the private key needs to be regenerated (e.g., due to loss or security issues), the associated address in the Symbiosis PoS Staking Contracts must be updated. Otherwise, the node will no longer be recognized by the network and cannot participate in relaying operations.

### 2. MPC Key Fragments

An MPC key (Multi-Party Computation key) is a cryptographic key that is generated and managed collectively by a group of relayer nodes. Instead of a single entity holding the full private key, each relayer node in the group holds only a fragment of the key. Together, the group can produce valid signatures without ever reconstructing the full key.

When a relayer node is selected as part of an MPC group for a given epoch, it generates and stores its fragment of the MPC private key. These fragments are used to:

* Sign cross-chain calldata during the epoch in which the MPC key is active.
* Update the MPC address stored in the Symbiosis Core Contracts when a new epoch begins — but only if the relayer node holds a key fragment corresponding to the current MPC address in the contracts.

For more information about the MPC key generation, see [Relayers Network: Architecture and Operations](/relayers-network/symbiosis-relayers-network-architecture-and-operations.md#epoch-change).

## Relayer Node Registration

To participate in the Symbiosis Relayers Network, relayer nodes must be registered in the Symbiosis PoS Staking Contracts.

This section outlines what is required for registration, which parameters can be updated later, and which are permanent.

**Roles Involved**

* A **Relayer Node Runner** is responsible for maintaining the relayer node: keeping it online, updating software, and managing infrastructure.
* A **Validator** provides the required **stake** by locking tokens in the **PoS Staking Contracts**. This stake supports the relayer node's operation and contributes to the network’s security.

**Note:** Typically, the Node Runner and Validator are the same entity, but this is not a strict requirement.

#### Information Required for Registration

Registration and staking occur in a **single transaction**. The following parameters must be provided:

* **Validator address**\
  The address from which the stake is provided. This address is permanent and cannot be changed after registration. To switch validator addresses, a new registration is required.
* **Stake Amount**\
  Tokens locked as collateral in the PoS Staking Contracts. The amount can be increased or decreased later, but must never fall below the minimum required threshold.
* **Relayer Node Address**\
  The address corresponding to the relayer node’s private key. If the private key is rotated, the address must be manually updated in the Staking Contracts for the node to remain active in the network.

{% hint style="info" %}
**Optional:** Validators registered in the PoS Staking Contracts can optionally register as Symbiotic Operators.\
This does not require additional staking but extends the validator’s role within the shared security layer provided by Symbiotic.
{% endhint %}

**Rewards**

Validators receive rewards based on the performance and contributions of the relayer nodes they support.

## Additional Information

<table data-card-size="large" data-view="cards"><thead><tr><th></th><th></th><th></th><th data-hidden data-card-target data-type="content-ref"></th></tr></thead><tbody><tr><td><strong>Economics and Security: Symbiosis PoS Staking &#x26; Symbiotic Staking</strong></td><td>Discover how Symbiosis PoS Staking and Symbiotic Staking secure the protocol, incentivize participants, and strengthen network resilience. Learn about the roles of <strong>Validators</strong>, <strong>Delegators</strong>, and <strong>Symbiotic Operators</strong>.<br></td><td><mark style="color:red;">Read more →</mark></td><td><a href="/pages/ktubJcEpVALdH2Wltww5">/pages/ktubJcEpVALdH2Wltww5</a></td></tr><tr><td><strong>Architecture and Operations: Symbiosis Relayers Network</strong></td><td>Explore the technical design of the Symbiosis Relayers Network, including its components, decentralized coordination mechanisms, and the execution of cross-chain operations. Understand how these elements work together to facilitate secure and efficient communication across blockchains.</td><td><mark style="color:red;">Read more →</mark></td><td><a href="/pages/zjHksOLesLBfIp156O6K">/pages/zjHksOLesLBfIp156O6K</a></td></tr></tbody></table>


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