# 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 ```javascript 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 ```javascript 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 ```javascript 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 ```javascript 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: ```json { "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](/pqc/mldsa44.md): Algorithm details * [PQC Overview](/pqc/overview.md): Why post-quantum cryptography * [Ethers SDK](/developers/overview-1.md): Working with transactions in code --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. 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