> For the complete documentation index, see [llms.txt](https://docs.hypertensor.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.hypertensor.org/subnet-template/authorizers.md).

# Authorizers

In decentralized networks, **secure communication between nodes is essential**. While nodes can freely call each other's RPC methods, it’s often critical to ensure that these communications are **authenticated** — meaning every message is cryptographically signed and verified.

Authorizers are in-between peer communications and are a powerful tool for security. Custom logic can be built to authenticate who, when, what, or why a node is requesting to responding to communication.

Authentication helps prevent a wide range of attacks and ensures that each message truly comes from a trusted peer.

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### **Why Authentication Matters**

#### Without authentication, any node in the network could:

* Impersonate another node
* Falsify data or responses
* Launch large-scale spam or Sybil attacks
* Eavesdrop on or manipulate communication between other nodes

#### By requiring messages to be signed and verified, subnets can:

* Establish **trust** between nodes
* Prevent **man-in-the-middle (MITM)** attacks
* Prevent **Sybil** attacks
* Enforce **staking, reputation, or voting systems**

### **Note**

If a subnet uses a specific authorizer or authorizers for communication, any new nodes that come in **must use the same authorizers**; otherwise, **they will be unable to connect**.

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### **Common Attack Vectors**

#### **🔐 Man-in-the-Middle (MITM) Attack**

A MITM attack occurs when an attacker intercepts or relays messages between two nodes without their knowledge. The attacker can read, alter, or inject messages — pretending to be the sender or receiver.

Authentication with digital signatures ensures that only the legitimate sender could have created the message, making MITM attacks ineffective.

#### **🔐**Sybil Attack

A Sybil attack is a type of security threat where an attacker creates multiple fake identities (also called "Sybils") to infiltrate a network and gain undue influence. This is done by having a single entity (like a computer or user account) control multiple fake identities, making it appear as if there are many distinct, legitimate users.