hash

Overview

The hash node generates cryptographic hashes and HMAC signatures from message payloads. Essential for data integrity verification, webhook signature validation, password hashing, deduplication by content fingerprint, and secure API authentication.

Properties

Algorithms

MD5:  32 hex characters
SHA1: 40 hex characters

Best for: deduplication,
file integrity checks

SHA256: 64 hex characters
SHA512: 128 hex characters

Best for: data integrity,
secure fingerprinting

Requires a secret key.
Uses SHA256 internally.

Best for: webhook validation,
API authentication

Example: SHA256 Data Integrity Verification

Hash sensor payloads to detect tampering or corruption in transit.

// Hash node configuration
{
  "algorithm": "SHA256",
  "encoding": "hex",
  "property": "payload",
  "output": "payload.hash"
}

// Input message:
{
  "payload": "temperature=24.5&humidity=62&sensor=BME280"
}

// Output message:
{
  "payload": {
    "data": "temperature=24.5&humidity=62&sensor=BME280",
    "hash": "a3f2b8c1e9d04567..."
  }
}

// Receiver can re-hash and compare to verify data integrity

Example: HMAC Webhook Signature Validation

Validate incoming webhook signatures from services like GitHub or Stripe.

// Hash node configuration
{
  "algorithm": "HMAC",
  "encoding": "hex",
  "key": "whsec_your_webhook_secret_key",
  "property": "payload"
}

// Flow: http-in → hash → switch → process
//
// 1. HTTP request arrives with:
//    Header: X-Signature: sha256=a1b2c3d4e5...
//    Body: {"event": "sensor.alert", "data": {...}}
//
// 2. Hash node computes HMAC of body
//    Result: "a1b2c3d4e5..."
//
// 3. Switch node compares:
//    msg.payload === msg.req.headers["x-signature"]
//    Match → process (trusted)
//    No match → reject (tampered)

Example: Content Deduplication

Use MD5 fingerprints to detect and drop duplicate messages.

// Hash node configuration
{
  "algorithm": "MD5",
  "encoding": "hex",
  "property": "payload",
  "output": "fingerprint"
}

// Flow: mqtt-in → hash → function (dedup) → process
//
// Function node checks against seen hashes:
var seen = flow.get("seen_hashes") || {};
if (seen[msg.fingerprint]) {
    return null;  // Drop duplicate
}
seen[msg.fingerprint] = Date.now();
flow.set("seen_hashes", seen);
return msg;

Common Use Cases