# Working with Online Transaction

The Online Transaction class extends the standard ITransaction interface implementation by adding functionality that requires chain API access. This provides enhanced verification capabilities and enables several important online transaction features that aren't available in offline transactions (such as created from TaPoS data, or directly using Protobuf or JSON objects).

# Overview

The Online Transaction class:

Inherits from the base ITransaction class
Adds online-specific functionality for chain verification
Enables security checks for operations to prevent accidental key leaks
Verifies account existence and authority requirements

# On-Chain Verification

One of the most powerful features of Online Transaction is the ability to perform on-chain verification:

Test it yourself: src/typescript/transaction/working-with-transaction/online-transaction/on-chain-verification.ts

import { createHiveChain } from '@hiveio/wax';

// Initialize hive chain interface
const chain = await createHiveChain();

// Initialize an online transaction object
const tx = await chain.createTransaction();

// Declare example operation
const operation = {
  vote_operation: {
    voter: "gtg",
    author: "gtg",
    permlink: "hello-world",
    weight: 2200
  }
};

// Push operation into the transction
tx.pushOperation(operation);

// Perform on-chain verification before broadcasting
try {
  await tx.performOnChainVerification();
  console.log('Transaction passed on-chain verification!');

  // Now safe to broadcast
  // await chain.broadcast(tx);
} catch (error) {
  console.error('Verification failed:', error.message);
}

TBA

This verification process includes:

Scanning for potential private key leaks in memos and comments
Ensuring referenced accounts exist on the blockchain
Validating authority changes in account operations

This verification process is automatically performed only on online transactions before broadcasting them. This way, you won't have to manually perform on-chain verification every time before broadcasting.

# On-Chain Operation Validation

The Online Transaction uses an internal on-chain operation validator class that performs various security checks:

Private Key Leak Prevention: Scans operation content (like memos and comments) for accidental inclusion of private keys
Account Existence Verification: Ensures referenced accounts exist on the blockchain
Authority Modification Safety: Checks for potentially dangerous authority changes

Example of what this prevents:

Test it yourself: src/typescript/transaction/working-with-transaction/online-transaction/on-chain-operation-validation.ts

import { createHiveChain } from '@hiveio/wax';

// Initialize hive chain interface
const chain = await createHiveChain();

// Initialize an online transaction object
const tx = await chain.createTransaction();

// Declare example operation
const operation = {
  transfer_operation: {
    from: "gtg",
    to: "friend",
    amount: chain.hiveCoins(5),
    // Would be caught:
    memo: 'Here is my private key: '
        + '5KQwrPbwdL6PhXujxW37FSSQZ1JiwsST4cqQzDeyXtP79zkvFD3'
  }
};

// Push operation into the transction
tx.pushOperation(operation);

// Perform on-chain verification before broadcasting
try {
  // The verification would fail before broadcasting

  // Throws error: "Potential private key leak detected!":
  await tx.performOnChainVerification();

  console.log('Verification successful!');
} catch (error) {
  console.error('Verification failed:', error.message);
}

TBA

# Authority Verification Trace

For debugging or advanced use cases, you can generate a detailed trace of authority verification:

Test it yourself: src/typescript/transaction/working-with-transaction/online-transaction/authority-verification-trace.ts

import { createHiveChain } from '@hiveio/wax';

// Initialize hive chain interface
const chain = await createHiveChain();

// Initialize a transaction object with already existing data
// (txid: 88e992c6094a6c6813f970b77abc4a6fee4a8a27)
const parsedTransaction = chain.createTransactionFromJson({
  "expiration": "2025-09-03T15:43:06",
  "extensions": [],
  "operations": [
    {
      "type": "custom_json_operation",
      "value": {
        "id": "notify",
        "json": "[\"setLastRead\",{\"date\":\"2025-09-03T15:31:07\"}]",
        "required_auths": [],
        "required_posting_auths": [
          "sandormb"
        ]
      }
    }
  ],
  "signatures": [
    "202cf9ea0754d1927a7875fdaf3aa6d743d7ffe4ccdc64059b9d6cb8e7"
    + "5ea1e5421e5d28d7205e6c820f8307c36e97b45da2bed6fa5795b3cf675020b77facdaee"
  ],
  "ref_block_num": 17420,
  "ref_block_prefix": 1854844897
});

const useLegacySerialization = false;

// Create an online transaction to perform online authority verification
const tx = await chain.createTransaction();
// Provide an external transaction for analysis
const trace = await tx.generateAuthorityVerificationTrace(
  useLegacySerialization,
  parsedTransaction
);

// Display the final trace
console.log(trace);

{
  "collectedData": [
    {
      "finalAuthorityPath": {
        "processedEntry": "sandormb",
        "processedRole": "posting",
        "threshold": 1,
        "weight": 1,
        "recursionDepth": 0,
        "processingStatus": {
          "entryAccepted": true,
          "isOpenAuthority": false
        },
        "visitedEntries": [
          {
            "processedEntry": "STM5M43EiFVh7eobDsPWeGGDQqUZohxgoBmR25hoz5GHMhNhKDknm",
            "processedRole": "posting",
            "threshold": 1,
            "weight": 1,
            "recursionDepth": 0,
            "processingStatus": {
              "entryAccepted": true,
              "isOpenAuthority": false
            },
            "visitedEntries": []
          }
        ]
      },
      "matchingSignatures": [
        {
          "signature": "202cf9ea0754d1927a7875fdaf3aa6d743d7ffe4ccdc64059b9d6cb8e75ea1e5421e5d28d7205e6c820f8307c36e97b45da2bed6fa5795b3cf675020b77facdaee",
          "signatureKey": "STM5M43EiFVh7eobDsPWeGGDQqUZohxgoBmR25hoz5GHMhNhKDknm"
        }
      ]
    }
  ],
  "rootEntries": [
    {
      "processedEntry": "sandormb",
      "processedRole": "posting",
      "threshold": 1,
      "weight": 1,
      "recursionDepth": 0,
      "processingStatus": {
        "entryAccepted": true,
        "isOpenAuthority": false
      },
      "visitedEntries": [
        {
          "processedEntry": "STM5M43EiFVh7eobDsPWeGGDQqUZohxgoBmR25hoz5GHMhNhKDknm",
          "processedRole": "posting",
          "threshold": 1,
          "weight": 1,
          "recursionDepth": 0,
          "processingStatus": {
            "entryAccepted": true,
            "isOpenAuthority": false
          },
          "visitedEntries": []
        }
      ]
    }
  ],
  "rootEntry": {
    "processedEntry": "sandormb",
    "processedRole": "posting",
    "threshold": 1,
    "weight": 1,
    "recursionDepth": 0,
    "processingStatus": {
      "entryAccepted": true,
      "isOpenAuthority": false
    },
    "visitedEntries": [
      {
        "processedEntry": "STM5M43EiFVh7eobDsPWeGGDQqUZohxgoBmR25hoz5GHMhNhKDknm",
        "processedRole": "posting",
        "threshold": 1,
        "weight": 1,
        "recursionDepth": 0,
        "processingStatus": {
          "entryAccepted": true,
          "isOpenAuthority": false
        },
        "visitedEntries": []
      }
    ]
  },
  "finalAuthorityPath": [
    {
      "processedEntry": "sandormb",
      "processedRole": "posting",
      "threshold": 1,
      "weight": 1,
      "recursionDepth": 0,
      "processingStatus": {
        "entryAccepted": true,
        "isOpenAuthority": false
      },
      "visitedEntries": [
        {
          "processedEntry": "STM5M43EiFVh7eobDsPWeGGDQqUZohxgoBmR25hoz5GHMhNhKDknm",
          "processedRole": "posting",
          "threshold": 1,
          "weight": 1,
          "recursionDepth": 0,
          "processingStatus": {
            "entryAccepted": true,
            "isOpenAuthority": false
          },
          "visitedEntries": []
        }
      ]
    }
  ],
  "verificationStatus": {
    "entryAccepted": true,
    "isOpenAuthority": false
  }
}

TBA

The trace can help understand:

Which signatures were used
Which authorities were satisfied
What authorities are still missing
The full verification path through nested authorities

By utilizing these features, we were able to create the Transaction Inspector app: