ethereumjs-tx-sign

Description:

The goal of this project is to provide a light-weight minimal library to sign (and verify) raw Ethereum transactions.

Installation:

npm install --save '@warren-bank/ethereumjs-tx-sign'

---

Background:

ethereumjs-tx is the de-facto library used to sign raw transactions.

Clean installation of the ethereumjs-tx module results in a node_modules directory that is:

• 10.4 MB
• 24.9 MB on disk (ext4)

Clean installation of this module results in a node_modules directory that is:

• 333.5 KB
• 640.0 KB on disk (ext4)

---

API:

{rawData, msgHash, DER, signature, rawTx} = sign(txData, privateKey)

• params:
  • txData
    • type: Object
    • keys can include: "nonce","gasPrice","gasLimit","to","value","data","chainId"
    • values:
      • type: String
      • format: hex-encoded (with '0x' prefix)
      • more generally: any value that can be converted to a Buffer: rlp.toBuffer(value)
      • exceptions:
        • "chainId":
          • type: native Number
          • notes:
            • EIP 155
            • value is used to modify msgHash
            • value is stored in rawData in the field corresponding to "v"
              (ie: the signature recovery shares its field with the chainId); consequently,
              value is stored in rawTx
  • privateKey
    • type: String
    • format: hex-encoded (with or without '0x' prefix)
• returns:
  • rawData
    • type: Array of Buffers
    • length: 9
    • values (and order) correspond to the data fields: "nonce","gasPrice","gasLimit","to","value","data","v","r","s"
  • msgHash
    • description: sha3 hash of RLP encoded Array containing the first 6 elements of rawData
      • note:
        • if chainId > 0: Array is extended to 9 elements
          • 7th: Buffer containing chainId
          • 8th and 9th: zero-length Buffers
    • type: String
    • format: hex-encoded (without '0x' prefix)
  • DER
    • description: DER encoded signature
    • type: Array of Number
    • format: each Number is an Integer in the range [0..255] and represents a single Byte
  • signature
    • Buffer
    • length: 64 Bytes
    • contents: rawData.r (32 Bytes) + rawData.s (32 Bytes)
  • rawTx
    • description: RLP encoded rawData
    • type: String
    • format: hex-encoded (without '0x' prefix)

Example:

const {sign} = require('@warren-bank/ethereumjs-tx-sign')

const txData = {
  nonce:    '0x00',
  gasPrice: '0x6fc23ac00',
  gasLimit: '0x2710',
//to:       '0x00',
  value:    '0x00',
  data:     '0x7f7465737432000000000000000000000000000000000000000000000000000000600057',
  chainId:  1
}

const privateKey = 'e922354a3e5902b5ac474f3ff08a79cff43533826b8f451ae2190b65a9d26158'

const {rawTx} = sign(txData, privateKey)

const Web3 = require('web3')
const web3 = new Web3()
web3.setProvider(new web3.providers.HttpProvider('http://localhost:8545'))

web3.eth.sendRawTransaction(rawTx, function(err, hash) {
  if (err)
    console.log('error:', err.message)
  if ((!err) && hash)
    console.log('transaction hash:', hash)
})

More Complete Example:

• script
• output

---

verify(msgHash, signature, publicKey)

• params:
  • msgHash
    • type: String
    • format: hex-encoded (without '0x' prefix)
  • signature
    • type:
      • Buffer: length of 64 Bytes
      • Object: {r, s}
        • r: Buffer w/ length of 32 Bytes
        • s: Buffer w/ length of 32 Bytes
      • (DER encoded) Array of Number
      • (DER encoded) String: hex-encoded (without '0x' prefix):
        let DER_string = require('elliptic').utils.encode(DER, 'hex')
  • publicKey
    • type: String
    • format: hex-encoded (with or without '0x' prefix)
• returns:
  • Boolean
    • indicates whether the signature can be verified for the msgHash using the publicKey
      • true indicates that the signature was originally created using the (unavailable) privateKey that is paired to the (available) publicKey
      • false indicates that it was not

Example:

// continuation of the previous example:

const {verify} = require('@warren-bank/ethereumjs-tx-sign')

{
  let {msgHash, signature} = sign(txData, privateKey)

  let publicKey = '0493ff3bd23838a02f24adcb23aa90bf2de8becbd1abe688e0f6a3202bee2cc4c2ecf7cd2608cda0817d6223f81bed074f166b8b55de54d603817699b4c70feaac'

  let result = verify(msgHash, signature, publicKey)
}

More Complete Example:

• script
• output

---

{txData, signature, msgHash, publicKey, address} = unsign(rawTx)

• params:
  • rawTx
    • type:
      • String: hex-encoded (with or without '0x' prefix)
      • Buffer
• returns:
  • txData
    • type: Object
    • keys: "nonce","gasPrice","gasLimit","to","value","data","chainId"
    • values:
      • type: String
      • format: hex-encoded (with '0x' prefix)
      • exceptions:
        • "chainId":
          • type: native Number
  • signature
    • type: Object
    • keys: "r","s"
    • values:
      • type: String
      • format: hex-encoded (without '0x' prefix)
  • msgHash
    • type: String
    • format: hex-encoded (without '0x' prefix)
  • publicKey
    • type: String
    • format: hex-encoded (without '0x' prefix)
  • address
    • description: "from" address … seen by network as the sender of this signed transaction
    • type: String
    • format: hex-encoded (without '0x' prefix)

Example:

// continuation of the previous example:

const {unsign} = require('@warren-bank/ethereumjs-tx-sign')

{
  let {txData, msgHash, signature, publicKey} = unsign(rawTx)

  let result = verify(msgHash, signature, publicKey)
}

More Complete Example:

• script
• output

Related:

• ethereumjs-tx-unsign
  • exports a variation of the function: unsign()
  • it is a minimal library to retrieve txData and (optionally) signature from rawTx
  • it doesn't include any external dependencies and (consequently) lacks the ability to calculate publicKey and address from signature

---

Bonus (Internal Library) APIs:

{privateKey, publicKey, address} = genKeyPair()

• returns:
  • privateKey
    • type: String
    • format: hex-encoded (without '0x' prefix)
  • publicKey
    • type: String
    • format: hex-encoded (without '0x' prefix)
  • address
    • type: String
    • format: hex-encoded (without '0x' prefix)

Example:

const {genKeyPair} = require('@warren-bank/ethereumjs-tx-sign/lib/keypairs')

const {privateKey, publicKey, address} = genKeyPair()

console.log({privateKey, publicKey, address})

Output:

{
  privateKey: 'e922354a3e5902b5ac474f3ff08a79cff43533826b8f451ae2190b65a9d26158',
  publicKey:  '0493ff3bd23838a02f24adcb23aa90bf2de8becbd1abe688e0f6a3202bee2cc4c2ecf7cd2608cda0817d6223f81bed074f166b8b55de54d603817699b4c70feaac',
  address:    'f95abdf6ede4c3703e0e9453771fbee8592d31e9'
}

More Complete Example:

• script
• output

---

publicKey = privateToPublic(privateKey, compressed)

• params:
  • privateKey
    • type:
      • String: hex-encoded (with or without '0x' prefix)
      • Buffer
  • compressed
    • description
    • type: Boolean
    • default: false
• returns:
  • publicKey
    • type: String
    • format: hex-encoded (without '0x' prefix)

Example:

// continuation of the previous example:

const {privateToPublic} = require('@warren-bank/ethereumjs-tx-sign/lib/keypairs')

{
  let pubKey = privateToPublic(privateKey)

  assert(pubKey === publicKey)
}

---

address = publicToAddress(publicKey)

• params:
  • publicKey
    • type:
      • String: hex-encoded (with or without '0x' prefix)
      • Buffer
• returns:
  • address
    • type: String
    • format: hex-encoded (without '0x' prefix)

Example:

// continuation of the previous example:

const {publicToAddress} = require('@warren-bank/ethereumjs-tx-sign/lib/keypairs')

{
  let addr = publicToAddress(publicKey)

  assert(addr === address)
}

---

hash = sha3(value, bits)

• params:
  • value
    • any value that can be converted to a Buffer: rlp.toBuffer(value)
  • bits
    • type: Number
    • supported values include: 224, 256, 384, 512
    • default: 256
• returns:
  • hash
    • type: String
    • format: hex-encoded (without '0x' prefix)

Example:

const {sha3} = require('@warren-bank/ethereumjs-tx-sign/lib/keccak')

{
  let hash = sha3('hello world')
}

---

Browser Bundle:

<script src="./browser-build/dist/js/bundle.js"></script>
<script>
{
  let Buffer = window.Buffer

  let BN = window.BN

  let {sign, verify, unsign} = window.ethereumjs_tx_sign

  let {privateToPublic, publicToAddress, genKeyPair} = window.ethereumjs_tx_sign.keypairs

  let {encode, isHexPrefixed, stripHexPrefix, stripZeros, intToHex, padToEven, intToBuffer, toBuffer, bufferToHex, bufferToInt} = window.ethereumjs_tx_sign.rlp

  let {createKeccakHash, sha3} = window.ethereumjs_tx_sign.keccak
}
</script>

Hosted Tests:

• examples in README
• keypairs

---

Credits (mostly) Belong To:

• ethereumjs-tx
• ethereumjs-util
• secp256k1-node
• rlp
• keccak

Special Thanks To:

• elliptic
  • is a dependency of this module
  • is the work-horse that makes all of this possible