Javascript

Using Javascript/node.js to sign and verify a transaction
Signing a transaction
This example would show how to sign a simple transaction
const secp256k1 = require('secp256k1');
const { bech32 } = require('bech32');
const createHash = require('create-hash');
const jsonStringify = require('fast-json-stable-stringify');
const bip39 = require('bip39');
const bip32 = require('bip32');
​
// the code of `seedToPrivateKey` is derived from @lunie/cosmos-key
// https://github.com/luniehq/cosmos-keys/blob/2586e7af82fc52c2c2603383e850a1969539f4f1/src/cosmos-keys.ts
function seedToPrivateKey(mnemonic, hdPath = `m/44'/118'/0'/0/0`) {
  const seed = bip39.mnemonicToSeedSync(mnemonic)
  const masterKey = bip32.fromSeed(seed)
  const { privateKey } = masterKey.derivePath(hdPath)
  return privateKey
}
​
function createSigner(privateKey) {
  console.log(`private key: ${privateKey.toString('hex')}`);
  const publicKeyArr = secp256k1.publicKeyCreate(privateKey, true);
  const publicKey = Buffer.from(publicKeyArr);
  console.log(`public key: ${publicKey.toString('base64')}`);
  const sha256 = createHash('sha256');
  const ripemd = createHash('ripemd160');
  sha256.update(publicKey);
  ripemd.update(sha256.digest());
  const rawAddr = ripemd.digest();
  const cosmosAddress = bech32.encode('cosmos', bech32.toWords(rawAddr));
  console.log(`address: ${cosmosAddress}`);
  const sign = (msg) => {
    const msgSha256 = createHash('sha256');
    msgSha256.update(msg);
    const msgHash = msgSha256.digest();
    const { signature: signatureArr } = secp256k1.ecdsaSign(msgHash, privateKey);
    const signature = Buffer.from(signatureArr)
    console.log(`signature: ${signature.toString('base64')}`);
    return { signature, publicKey };
  }
  return { cosmosAddress, sign };
}
​
const privKey = Buffer.from('0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef', 'hex');
// may also derive private key from seed words:
// const seed = "novel novel novel novel novel novel novel novel novel novel novel novel novel novel novel novel novel novel novel novel novel novel novel novel";
// const privKey = seedToPrivateKey(seed);
const signer = createSigner(privKey);
const signBytes = jsonStringify({
  "fee": {
    "amount": [
      {
        "denom": "nanolike",
        "amount": "100000000"
      }
    ],
    "gas": "100000"
  },
  "msgs": [
    {
      "type": "cosmos-sdk/MsgSend",
      "value": {
        "from_address": "cosmos1mnyn7x24xj6vraxeeq56dfkxa009tvhgknhm04",
        "to_address": "cosmos1ca0zlqxjqv5gek5qxm602umtkmu88564hpyws4",
        "amount": [
          {
            "denom": "nanolike",
            "amount": "123456789"
          }
        ]
      }
    }
  ],
  "chain_id": "likechain-testnet-taipei-1",
  "account_number": "21",
  "sequence": "0",
  "memo": "",
});
signer.sign(signBytes);
​
// private key: 0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef
// public key: A0ZGrlBHMWtCMNAIbIrOxofwCxzZ0dxjT2yzWKwKmo//
// address: cosmos1mnyn7x24xj6vraxeeq56dfkxa009tvhgknhm04
// signature: iBIA5d+tZ99hlcjdzvpm8/eHtK31kblp1lCHWb4CSzEQUm/Wns/emogUn6VsSQVt2eYPpLjnfNXas5PMgWzdnw==
Broadcasting a signed transaction
Then we can format our transaction for calling the chain RPC API POST /txs, to broadcast our signed transaction.
{
    "mode": "sync",
    "tx": {
        "msg": [
            {
                "type": "cosmos-sdk/MsgSend",
                "value": {
                "from_address": "cosmos1mnyn7x24xj6vraxeeq56dfkxa009tvhgknhm04",
                "to_address": "cosmos1ca0zlqxjqv5gek5qxm602umtkmu88564hpyws4",
                    "amount": [
                        {
                            "denom": "nanolike",
                            "amount": "123456789"
                        }
                    ]
                }
            }
        ],
        "fee": {
            "amount": [
                {
                    "denom": "nanolike",
                    "amount": "100000000"
                }
            ],
            "gas": "100000"
        },
        "memo": "",
        "signatures": [
            {
                "signature": "iBIA5d+tZ99hlcjdzvpm8/eHtK31kblp1lCHWb4CSzEQUm/Wns/emogUn6VsSQVt2eYPpLjnfNXas5PMgWzdnw==",
                "pub_key": {
                    "type": "tendermint/PubKeySecp256k1",
                    "value": "A0ZGrlBHMWtCMNAIbIrOxofwCxzZ0dxjT2yzWKwKmo//"
                }
            }
        ]
    }
}
For details of the POST /txs and other chain RPC API, please refer to the LikeCoin chain RPC API section.
Verifying a signed transaction
For verifying a transaction, we would need to know the public key of the signature.
const secp256k1 = require('secp256k1');
const createHash = require('create-hash');
​
const signature = Buffer.from('iBIA5d+tZ99hlcjdzvpm8/eHtK31kblp1lCHWb4CSzEQUm/Wns/emogUn6VsSQVt2eYPpLjnfNXas5PMgWzdnw==', 'base64');
const publicKey = Buffer.from('A0ZGrlBHMWtCMNAIbIrOxofwCxzZ0dxjT2yzWKwKmo//', 'base64');
const msg = '{"account_number":"21","chain_id":"likechain-testnet-taipei-1","fee":{"amount":[{"amount":"100000000","denom":"nanolike"}],"gas":"100000"},"memo":"","msgs":[{"type":"cosmos-sdk/MsgSend","value":{"amount":[{"amount":"123456789","denom":"nanolike"}],"from_address":"cosmos1mnyn7x24xj6vraxeeq56dfkxa009tvhgknhm04","to_address":"cosmos1ca0zlqxjqv5gek5qxm602umtkmu88564hpyws4"}}],"sequence":"0"}'
const msgSha256 = createHash('sha256');
msgSha256.update(msg);
const msgHash = msgSha256.digest();
console.log(secp256k1.ecdsaVerify(signature, msgHash, publicKey));
​
// true
​
Sample
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Last updated 1 month ago