Transaction Types

Armchain introduces Type 3 transactions for post-quantum cryptography. If you're using the Armchain Ethers SDK, this is handled automatically. The SDK creates and signs Type 3 transactions for you. This page is for developers who want to understand the format details or build custom tooling.

Transaction Type Summary

Type	Name	EIP	Signature	Supported
0	Legacy	Pre-EIP-2718	ECDSA	No
1	Access List	EIP-2930	ECDSA	No
2	EIP-1559	EIP-1559	ECDSA	No
3	PQC (Armchain)	-	ML-DSA44	Yes

Armchain only supports Type 3 transactions. ECDSA-signed transactions (Types 0, 1, 2) are rejected by the network.

Type 3 Transaction Format

Fields

Field	Type	Description
type	uint8	Always 0x03
chainId	uint64	Chain ID (55 devnet)
nonce	uint64	Sender account nonce
maxPriorityFeePerGas	uint256	Tip for the validator (EIP-1559)
maxFeePerGas	uint256	Maximum total gas price (EIP-1559)
gasLimit	uint64	Maximum gas for execution
to	address	Recipient (null for contract creation)
value	uint256	ARM amount in wei
data	bytes	Calldata or constructor bytecode
accessList	[]tuple	Storage access list (EIP-2930)
signatureBlob	bytes	ML-DSA44 signature + public key

Signature Blob

The signatureBlob field contains the concatenation of the ML-DSA44 signature and the public key:

signatureBlob (3,732 bytes)

ML-DSA44 does not support public key recovery, so both the signature and the public key are included in the blob.

RLP Encoding

Type 3 transactions use typed transaction envelopes (EIP-2718):

Serialized = 0x03 || RLP([
    chainId,
    nonce,
    maxPriorityFeePerGas,
    maxFeePerGas,
    gasLimit,
    to,
    value,
    data,
    accessList,
    signatureBlob
])

The signing payload (hash that is signed) is:

sigHash = Keccak256(0x03 || RLP([
    chainId,
    nonce,
    maxPriorityFeePerGas,
    maxFeePerGas,
    gasLimit,
    to,
    value,
    data,
    accessList
]))

The signature is computed over the sigHash, then the signatureBlob (signature + public key) is appended to the transaction fields.

Creating Type 3 Transactions

Using the Ethers SDK

import { ethers } from "@armchain-ethersv6/ethers";

const provider = new ethers.JsonRpcProvider("https://www.armchain.org/devnet");
const wallet = new ethers.Wallet(PRIVATE_KEY, provider);

// Simple transfer
const tx = await wallet.sendTransaction({
  to: "0xRecipientAddress",
  value: ethers.parseEther("1.0"),
  type: 3, // PQC transaction type
});

console.log("TX hash:", tx.hash);
const receipt = await tx.wait();
console.log("Confirmed in block:", receipt.blockNumber);

Manual Transaction Construction

import { ethers } from "@armchain-ethersv6/ethers";

const provider = new ethers.JsonRpcProvider("https://www.armchain.org/devnet");
const wallet = new ethers.Wallet(PRIVATE_KEY, provider);

// Build a transaction manually
const txRequest = {
  type: 3,
  chainId: 55,
  to: "0xRecipientAddress",
  value: ethers.parseEther("1.0"),
  nonce: await provider.getTransactionCount(wallet.address),
  maxFeePerGas: ethers.parseUnits("100", "gwei"),
  maxPriorityFeePerGas: ethers.parseUnits("1", "gwei"),
  gasLimit: 21000n,
};

// Sign (produces the signatureBlob internally)
const signedTx = await wallet.signTransaction(txRequest);

// Broadcast
const response = await provider.broadcastTransaction(signedTx);
console.log("TX hash:", response.hash);

Contract Deployment

const factory = new ethers.ContractFactory(abi, bytecode, wallet);
const contract = await factory.deploy(/* constructor args */, {
  type: 3,
});
await contract.waitForDeployment();
console.log("Deployed at:", await contract.getAddress());

Contract Interaction

const contract = new ethers.Contract(contractAddress, abi, wallet);

// Read (no transaction needed)
const value = await contract.someViewFunction();

// Write (creates a Type 3 transaction)
const tx = await contract.someFunction(arg1, arg2, {
  type: 3,
});
await tx.wait();

JSON-RPC Representation

When queried via JSON-RPC (eth_getTransactionByHash), Type 3 transactions include:

{
  "type": "0x3",
  "chainId": "0x37",
  "nonce": "0x0",
  "maxPriorityFeePerGas": "0x3b9aca00",
  "maxFeePerGas": "0x174876e800",
  "gas": "0x5208",
  "to": "0x...",
  "value": "0xde0b6b3a7640000",
  "input": "0x",
  "accessList": [],
  "signatureBlob": "0x...",
  "hash": "0x...",
  "blockHash": "0x...",
  "blockNumber": "0x1",
  "transactionIndex": "0x0"
}

Note: Type 3 transactions do NOT have v, r, s fields. They have a single signatureBlob field instead.

Size Comparison

Component	Type 2 (ECDSA)	Type 3 (ML-DSA44)
Transaction fields	~45 bytes	~45 bytes
Signature	65 bytes (v, r, s)	2,420 bytes (raw ML-DSA44)
Public key	0 bytes (recovered from signature)	1,312 bytes (appended to signature)
Signature blob total	65 bytes	3,732 bytes
Total (simple transfer)	~110 bytes	~3,930 bytes

The ~36x increase in transaction size is the cost of quantum resistance. Impact:

• Bandwidth: More data to propagate between nodes
• Storage: Larger blocks on disk
• Intrinsic gas: Higher data-related gas costs

However, it does NOT impact:

• Execution gas: EVM computation costs are identical
• Finality time: Still instant (Lachesis aBFT)
• Throughput: Block gas limits accommodate the larger transactions

Validation Rules

When a Type 3 transaction arrives at a node, the following checks are performed:

1. Type check: Transaction type must be 0x03
2. Chain ID check: Must match the node's chain ID
3. Signature blob size: Must be exactly 3,732 bytes (2,420 + 1,312)
4. ML-DSA44 verification: Verify the signature over the signing hash using the public key from the signature blob
5. Address derivation: The sender address (from) is derived from the public key: Keccak256(pubkey)[12:]
6. Nonce check: Must match the sender's current nonce
7. Balance check: Sender must have sufficient ARM for value + gas * maxFeePerGas
8. Gas limit check: Must be at least the intrinsic gas

If any check fails, the transaction is rejected and not propagated.

Further Reading

• ML-DSA44 Deep Dive: Algorithm details
• PQC Overview: Why post-quantum cryptography
• Ethers SDK: Working with transactions in code