# FAQ

Quick answers to the most common questions about Armchain. If your question isn't here, check the [Glossary](/resources/glossary.md) for terminology or visit the community Discord.

## General

### What is Armchain?

Armchain is a Layer 1 blockchain combining **EVM compatibility** with **post-quantum cryptography**. It uses Lachesis aBFT consensus for instant finality and ML-DSA44 (FIPS 204) for quantum-resistant signing.

### How is Armchain different from Ethereum?

| Feature          | Ethereum                | Armchain                    |
| ---------------- | ----------------------- | --------------------------- |
| Consensus        | Proof of Stake (Gasper) | Lachesis aBFT (DAG-based)   |
| Finality         | \~12 minutes            | **Instant**                 |
| Cryptography     | ECDSA (secp256k1)       | **ML-DSA44** (post-quantum) |
| Transaction Type | 0, 1, 2                 | **3** (PQC only)            |
| EVM              | Yes                     | Yes (London)                |

### Is Armchain EVM compatible?

Yes. Standard Solidity and Vyper contracts deploy on Armchain without modification. All EVM opcodes, precompiles, and ABI encoding work identically.

### What is the native token?

**ARM** is used for gas fees, validator staking, and governance.

***

## Post-Quantum Cryptography

### Why does Armchain use post-quantum cryptography?

Current blockchains use ECDSA, which can be broken by a sufficiently powerful quantum computer using Shor's algorithm. Armchain uses ML-DSA44 (a NIST-standardized post-quantum algorithm) to ensure that transactions and keys remain secure even in a post-quantum world.

### What is ML-DSA44?

ML-DSA44 (Module-Lattice Digital Signature Algorithm, Level 2) is a digital signature scheme standardized by NIST in FIPS 204. It provides \~128-bit security against both classical and quantum computers.

### Are quantum computers a real threat today?

Not yet for breaking cryptography. However, the **"harvest now, decrypt later"** attack is a current concern: adversaries store signed data today for later decryption when quantum computers become available. Armchain provides protection from day one.

### Why are transactions larger on Armchain?

ML-DSA44 signatures are inherently larger than ECDSA (3,732 bytes vs 65 bytes). The public key must also be included in every transaction (1,312 bytes) because ML-DSA44 does not support public key recovery. This results in \~3,930-byte simple transfers vs \~110 bytes with ECDSA.

### Can I use my Ethereum private key on Armchain?

No. ECDSA private keys are incompatible with Armchain. Generate ML-DSA44 keys using the Armchain Wallet or `@armchain-ethersv6/ethers`.

***

## Development

### Can I use Hardhat with Armchain?

Yes. Install `@armchain-ethersv6/ethers` and configure Hardhat with Armchain's RPC URL and chain ID. See [Quickstart](/get-started/quickstart.md).

### Can I use Foundry with Armchain?

Foundry can be used for compilation and read-only interactions (`cast call`). Deployment and write transactions require ML-DSA44 signing, which Foundry does not natively support. Use Hardhat or the Ethers SDK instead. See [Smart Contracts Overview](/developers/overview.md).

### What Solidity version should I use?

Armchain supports Solidity `^0.8.x`. Recommended: `0.8.24` or later.

### How do I verify contracts on the explorer?

Use the Armchain Explorer's contract verification tool. Submit source code, compiler version, and constructor arguments. See [Explorer](/tools/explorer.md).

### What is the gas limit for blocks?

The maximum block gas is **20,500,000**. Minimum gas price is **1 Gwei**.

***

## Wallet

### How do I create a wallet?

Install the Armchain Wallet browser extension, or create a wallet programmatically:

```javascript
import { ethers } from "@armchain-ethersv6/ethers";
const wallet = ethers.Wallet.createRandom();
console.log(wallet.address);
```

### What derivation path does Armchain use?

```
m/44'/65536'/account'/0/address'
```

All indices are hardened. Coin type is `65536`.

### How do I back up my wallet?

Write down your **12-word recovery phrase** and store it offline in a secure location. This phrase recovers all derived accounts.

***

## Node Operations

### How do I run a validator?

Build the `opera` binary, generate ML-DSA44 validator keys, stake ARM, and register. See [Running a Validator](https://github.com/khizarbakhtiar1/dev-docs/blob/main/node-operators/running-a-validator.md).

### What ports need to be open?

| Port  | Protocol | Purpose                                  |
| ----- | -------- | ---------------------------------------- |
| 5050  | TCP/UDP  | P2P networking                           |
| 18545 | TCP      | HTTP JSON-RPC (optional, for API access) |
| 18546 | TCP      | WebSocket JSON-RPC (optional)            |

### How do I set up a local development network?

Use fakenet mode:

```bash
armnode --fakenet 1/1
```

See [Fakenet Guide](/node-operators/fakenet.md).

***

## Troubleshooting

### My transaction is failing with "transaction type not supported"

Ensure you're using `type: 3` in all transactions. Armchain only supports Type 3 (PQC) transactions.

### My transaction is failing with "invalid signature"

Ensure you're using ML-DSA44 keys (not ECDSA). Generate new keys with `ethers.Wallet.createRandom()` from `@armchain-ethersv6/ethers`.

### I can't connect to the node

* Check that the node is running and fully synced
* Verify the RPC URL and port (default: 18545 for HTTP)
* Ensure the RPC endpoint is enabled (`--http --http.addr 0.0.0.0 --http.port 18545`)
* Check firewall rules

### My dApp doesn't detect the Armchain Wallet

* Ensure the extension is installed and enabled
* Refresh the page
* Check that your code listens for `window.ethereum`

### The explorer shows "pending" for my transaction

Armchain has instant finality; transactions confirm in seconds. If a transaction stays pending:

* Verify the gas price is at least 1 Gwei
* Check that the nonce is correct
* Ensure the sender has sufficient ARM balance


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