Production-ready HMAC signature generation for API authentication, webhooks, and third-party integrations. Cross-platform compatible with PHP, Python, Java.
npm install hmac-auth-builderEnterprise-Grade HMAC Signature Generation for API Authentication
Cross-platform β’ Type-Safe β’ Zero Dependencies β’ Battle-Tested






Installation β’ Quick Start β’ API Reference β’ Examples β’ Security
---
- Why hmac-auth-builder?
- Installation
- Quick Start
- Core Concepts
- API Reference
- generateSignature()
- verifySignature()
- Configuration Options
- Usage Examples
- Express.js Integration
- Cross-Platform Compatibility
- Security Best Practices
- Performance
- Roadmap
- Contributing
- Author
- License
---
Building secure API authentication for webhooks and third-party integrations is hard. Common challenges include:
- β JSON serialization inconsistencies across languages (PHP, Python, Node.js produce different outputs)
- β Replay attack vulnerabilities when using simple API keys
- β Complex cryptographic implementations prone to security flaws
- β Lack of standardization leading to incompatible integrations
hmac-auth-builder solves these problems with a production-ready, cross-platform HMAC signature system used by companies integrating with:
- Financial services APIs (Decentro, Digio, payment gateways)
- Webhook providers (Stripe-style authentication)
- Microservice architectures (service-to-service auth)
- IoT device authentication
| Feature | hmac-auth-builder | Alternatives |
| ------------------------------ | ----------------------------- | -------------------------- |
| Cross-Platform Determinism | β
Canonical string signing | β JSON-based (unreliable) |
| Replay Attack Prevention | β
Built-in timestamp + nonce | β οΈ Manual implementation |
| Type Safety | β
Full TypeScript support | β οΈ JavaScript only |
| Zero Dependencies | β
Native crypto module | β Heavy dependencies |
| Express Middleware Ready | β
Drop-in integration | β οΈ Custom wrappers needed |
| Documentation Quality | β
Enterprise-grade | β οΈ Basic examples |
---
``bashnpm
npm install hmac-auth-builder
Requirements:
- Node.js β₯ 14.17.0
- TypeScript β₯ 4.5 (optional, but recommended)
---
π Quick Start
$3
`typescript
import { HmacOperations } from "hmac-auth-builder";// 1. Generate signature for outgoing request
const { timestamp, nonce, signature } = HmacOperations.generateSignature(
{
transaction_id: "TXN-2026-001",
amount: 5000,
currency: "USD",
},
"your-secret-key",
);
// 2. Send in HTTP headers
const response = await fetch("https://api.example.com/webhook", {
method: "POST",
headers: {
"X-Timestamp": timestamp.toString(),
"X-Nonce": nonce,
"X-Signature": signature,
"Content-Type": "application/json",
},
body: JSON.stringify({ transaction_id: "TXN-2026-001", amount: 5000 }),
});
// 3. Verify incoming webhook signature
const isValid = HmacOperations.verifySignature(
req.body, // Incoming payload
clientSecret, // Retrieve from secure storage
req.headers["x-signature"], // Signature from headers
req.headers["x-timestamp"],
req.headers["x-nonce"],
);
if (isValid.valid) {
// β
Signature verified - process webhook
} else {
// β Invalid signature - reject request
console.error(isValid.error);
}
`---
π§© Core Concepts
$3
`
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β SIGNATURE GENERATION β
βββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ€
β β
β 1. Canonical String Creation β
β timestamp|nonce|field1|field2|field3 β
β β β
β 2. HMAC-SHA256 with Secret Key β
β HMAC(secret, canonical_string) β
β β β
β 3. Hex/Base64 Encoding β
β a3f7b8c2d9e1f5g6h4i8j2k7l9m3n5o1... β
β β
ββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ
β SIGNATURE VERIFICATION β
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β β
β 1. Receive: timestamp, nonce, signature, payload β
β 2. Timestamp Check (prevent old requests) β
β 3. Nonce Check (prevent replay attacks) β
β 4. Regenerate signature with same algorithm β
β 5. Timing-safe comparison β
β received_sig === computed_sig ? β
: β β
β β
βββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββββ
`$3
Problem:
JSON.stringify() produces different outputs across platforms:`javascript
// Node.js
JSON.stringify({b: 2, a: 1}) // {"b":2,"a":1}// PHP
json_encode(['b' => 2, 'a' => 1]) // {"a":1,"b":2} β Different order!
// Python
json.dumps({'b': 2, 'a': 1}) // {"b": 2, "a": 1} β Extra spaces!
`Solution: Canonical string with explicit field order:
`javascript
// All languages produce: "timestamp|nonce|1|2"
canonicalString = ${timestamp}|${nonce}|${payload.a}|${payload.b};
`This guarantees identical signatures across all platforms.
---
π API Reference
$3
Generates cryptographically secure HMAC signature with timestamp and nonce for API request authentication.
#### Signature
`typescript
HmacOperations.generateSignature(
payload: Record,
secretKey: string,
config?: HmacConfig
): SignatureResult
`#### Parameters
| Parameter | Type | Required | Description |
| ----------- | --------------------- | -------- | -------------------------------------- |
|
payload | Record | β
Yes | Data object to sign (min 1 field) |
| secretKey | string | β
Yes | Secret key for HMAC (min 8 characters) |
| config | HmacConfig | βͺ No | Configuration options (see below) |#### Returns:
SignatureResult`typescript
{
timestamp: number | string; // Generated timestamp
nonce: string; // Generated nonce (UUID/hex)
signature: string; // HMAC signature (hex/base64)
algorithm: string; // Hash algorithm used
encoding: string; // Output encoding format
canonicalString: string; // Debug: string that was signed
}
`#### Example
`typescript
const result = HmacOperations.generateSignature(
{
user_id: "12345",
action: "transfer",
amount: 1000,
},
"sk_prod_a1b2c3d4e5f6",
);console.log(result);
// {
// timestamp: 1737623400000,
// nonce: '550e8400-e29b-41d4-a716-446655440000',
// signature: 'a3f7b8c2d9e1f5g6h4i8j2k7l9m3n5o1...',
// algorithm: 'sha256',
// encoding: 'hex',
// canonicalString: '1737623400000|550e8400...|12345|transfer|1000'
// }
`#### Error Handling
`typescript
try {
const result = HmacOperations.generateSignature(payload, secret);
} catch (error) {
// Throws detailed validation errors:
// - "Payload cannot be an empty object"
// - "Secret key is too short (5 characters). Minimum 8 required"
// - "canonicalFields contains fields not present in payload: xyz"
console.error(error.message);
}
`---
$3
Verifies HMAC signature received from external party. Implements timing-safe comparison and replay attack prevention.
#### Signature
`typescript
HmacOperations.verifySignature(
payload: Record,
secretKey: string,
receivedSignature: string,
receivedTimestamp: string | number,
receivedNonce: string,
config?: VerificationConfig
): VerificationResult
`#### Parameters
| Parameter | Type | Required | Description |
| ------------------- | --------------------- | -------- | ------------------------------ |
|
payload | Record | β
Yes | Received payload to verify |
| secretKey | string | β
Yes | Secret key for verification |
| receivedSignature | string | β
Yes | Signature from request headers |
| receivedTimestamp | string \| number | β
Yes | Timestamp from request headers |
| receivedNonce | string | β
Yes | Nonce from request headers |
| config | VerificationConfig | βͺ No | Verification options |#### Returns:
VerificationResult`typescript
{
valid: boolean; // true if signature is valid
error?: string; // Error message if invalid
expected?: string; // Expected signature (debug)
received?: string; // Received signature (debug)
timestampAge: number; // Age of timestamp in milliseconds
}
`#### Example
`typescript
// Server-side verification
const verification = HmacOperations.verifySignature(
req.body, // { transaction_id: 'TXN123' }
getClientSecret(clientId), // 'sk_client_xyz123'
req.headers["x-signature"], // 'a3f7b8c2d9e1f5g6...'
parseInt(req.headers["x-timestamp"]), // 1737623400000
req.headers["x-nonce"], // '550e8400-e29b...'
{
timestampTolerance: 180000, // Accept requests up to 3 min old
},
);if (verification.valid) {
console.log("β
Signature valid");
console.log(
Request age: ${verification.timestampAge}ms);
// Process request
} else {
console.error("β Invalid signature:", verification.error);
// Reject request - possible attack!
}
`#### Verification Errors
| Error Message | Cause | Solution |
| ------------------------------ | ---------------------------------- | ----------------------- |
|
"Signature mismatch" | Tampered payload or wrong secret | Check payload integrity |
| "Timestamp expired" | Request too old | Client should retry |
| "Duplicate request detected" | Nonce already used (replay attack) | Reject request |---
$3
####
HmacConfig InterfaceComplete configuration object for signature generation and verification.
`typescript
interface HmacConfig {
// Signature Method
signatureMethod?: "canonical" | "json"; // Default: 'canonical' // Canonical String Options
separator?: string; // Default: '|'
canonicalFields?: string[]; // Default: auto-sorted keys
// Cryptography
hashAlgorithm?: "sha256" | "sha512" | "sha384" | "sha1" | "md5";
encoding?: "hex" | "base64" | "base64url"; // Default: 'hex'
charset?: "utf8" | "ascii" | "latin1"; // Default: 'utf8'
// Timestamp
timestampFormat?: "milliseconds" | "seconds" | "unix" | "iso8601";
customTimestamp?: string | number; // For testing
includeTimestampInSignature?: boolean; // Default: true
// Nonce
nonceFormat?:
| "uuid-v4"
| "uuid-v1"
| "random-hex"
| "random-base64"
| "custom";
customNonce?: string; // For testing
customNonceGenerator?: () => string; // Custom function
includeNonceInSignature?: boolean; // Default: true
// JSON Method (when signatureMethod: 'json')
sortJsonKeys?: boolean; // Default: true
}
`#### Configuration Examples
1. Custom Field Order (for third-party compatibility)
`typescript
const config: HmacConfig = {
canonicalFields: ["timestamp", "merchant_id", "order_id", "amount"],
separator: "::",
};// Produces: "1737623400000::M123::ORD456::5000"
`2. Stronger Cryptography (for sensitive data)
`typescript
const config: HmacConfig = {
hashAlgorithm: "sha512",
encoding: "base64",
};
`3. ISO 8601 Timestamps (for international APIs)
`typescript
const config: HmacConfig = {
timestampFormat: "iso8601",
};
// Produces: "2026-01-23T12:30:00.000Z"
`4. Custom Nonce Generator (for compliance)
`typescript
const config: HmacConfig = {
nonceFormat: "custom",
customNonceGenerator: () =>
REQ-${Date.now()}-${Math.random().toString(36).substr(2, 9)},
};
// Produces: "REQ-1737623400000-k3j4h5g6"
`5. Fixed Values (for unit testing)
`typescript
const config: HmacConfig = {
customTimestamp: 1700000000000,
customNonce: "test-nonce-12345",
};
// Always produces same signature - perfect for deterministic tests
`####
VerificationConfig InterfaceExtended configuration for signature verification.
`typescript
interface VerificationConfig extends HmacConfig {
timestampTolerance?: number; // Max age in ms (default: 180000 = 3 min)
}
`Example:
`typescript
const verifyConfig: VerificationConfig = {
signatureMethod: "canonical",
timestampTolerance: 300000, // 5 minutes
};
`---
π‘ Usage Examples
$3
`typescript
import { HmacOperations } from "hmac-auth-builder";// Webhook provider (your server sending webhook)
const webhookPayload = {
event: "payment.completed",
transaction_id: "TXN-2026-12345",
amount: 5000,
currency: "USD",
};
const { timestamp, nonce, signature } = HmacOperations.generateSignature(
webhookPayload,
process.env.WEBHOOK_SECRET!,
);
// Send HTTP POST with headers
await fetch("https://client.example.com/webhook", {
method: "POST",
headers: {
"X-Timestamp": timestamp.toString(),
"X-Nonce": nonce,
"X-Signature": signature,
"Content-Type": "application/json",
},
body: JSON.stringify(webhookPayload),
});
`$3
`typescript
const algorithms = ["sha256", "sha512", "sha384"] as const;for (const algo of algorithms) {
const result = HmacOperations.generateSignature(
{ data: "test" },
"secret-key",
{ hashAlgorithm: algo },
);
console.log(
${algo}:, result.signature);
}// Output:
// sha256: a3f7b8c2d9e1f5g6h4i8j2k7l9m3n5o1...
// sha512: x9y8z7w6v5u4t3s2r1q0p9o8n7m6l5k4... (longer)
// sha384: m1n2o3p4q5r6s7t8u9v0w1x2y3z4a5b6...
`$3
`typescript
const encodings = ["hex", "base64", "base64url"] as const;for (const encoding of encodings) {
const result = HmacOperations.generateSignature(
{ user_id: "123" },
"secret-key",
{ encoding },
);
console.log(
${encoding}:, result.signature);
}// Output:
// hex: a3f7b8c2d9e1f5g6h4i8j2k7l9m3n5o1...
// base64: o/e4wtnh9fbEiMpx+c01...
// base64url: o_e4wtnh9fbEiMpx-c01... (URL-safe, no padding)
`$3
`typescript
// Must match order with third-party provider
const result = HmacOperations.generateSignature(
{
merchant_id: "M12345",
order_id: "ORD789",
amount: 1000,
timestamp: Date.now(),
},
"merchant-secret-key",
{
canonicalFields: ["merchant_id", "order_id", "amount", "timestamp"],
separator: "|",
},
);console.log(result.canonicalString);
// "1737623400000|550e8400-e29b...|M12345|ORD789|1000|1737623400000"
// ^timestamp ^nonce ^fields in exact order specified
`$3
When you need to sign entire JSON (with sorted keys):
`typescript
const result = HmacOperations.generateSignature(
{
transaction: {
id: "TXN123",
amount: 5000,
},
metadata: {
ip: "192.168.1.1",
device: "mobile",
},
},
"secret-key",
{
signatureMethod: "json",
sortJsonKeys: true, // Ensures deterministic JSON
},
);console.log(result.canonicalString);
// '{"metadata":{"device":"mobile","ip":"192.168.1.1"},"transaction":{"amount":5000,"id":"TXN123"}}'
// Keys are sorted alphabetically at all nesting levels
`---
Express.js Middleware
$3
`typescript
import express, { Request, Response, NextFunction } from "express";
import { HmacOperations } from "hmac-auth-builder";
import Redis from "ioredis";const app = express();
const redis = new Redis();
// Extend Request type
interface AuthenticatedRequest extends Request {
authenticatedClient?: string;
}
/**
* HMAC signature validation middleware
* Prevents unauthorized access and replay attacks
*/
export async function validateHmacSignature(
req: AuthenticatedRequest,
res: Response,
next: NextFunction,
): Promise {
try {
// 1. Extract authentication headers
const clientId = req.headers["x-client-id"] as string;
const timestamp = req.headers["x-timestamp"] as string;
const nonce = req.headers["x-nonce"] as string;
const signature = req.headers["x-signature"] as string;
// 2. Validate all headers present
if (!clientId || !timestamp || !nonce || !signature) {
res.status(401).json({
error: "Missing authentication headers",
required: ["X-Client-Id", "X-Timestamp", "X-Nonce", "X-Signature"],
});
return;
}
// 3. Get client secret from secure storage
const clientSecret = await getClientSecret(clientId);
if (!clientSecret) {
await logSecurityEvent("INVALID_CLIENT", { clientId });
res.status(401).json({ error: "Invalid client credentials" });
return;
}
// 4. Check nonce (prevent replay attacks)
const nonceKey =
nonce:${clientId}:${nonce};
const nonceExists = await redis.exists(nonceKey); if (nonceExists) {
await logSecurityEvent("REPLAY_ATTACK", { clientId, nonce });
res.status(409).json({
error: "Duplicate request detected",
details: "This nonce has already been used",
});
return;
}
// 5. Verify HMAC signature
const verification = HmacOperations.verifySignature(
req.body,
clientSecret,
signature,
parseInt(timestamp),
nonce,
{
signatureMethod: "canonical",
timestampTolerance: 180000, // 3 minutes
},
);
if (!verification.valid) {
await logSecurityEvent("INVALID_SIGNATURE", {
clientId,
error: verification.error,
timestampAge: verification.timestampAge,
});
res.status(403).json({
error: "Invalid signature",
details: verification.error,
});
return;
}
// 6. Store nonce to prevent reuse (5 min TTL)
await redis.setex(nonceKey, 300, "1");
// 7. Log successful authentication
await logSecurityEvent("AUTH_SUCCESS", {
clientId,
endpoint: req.path,
timestampAge: verification.timestampAge,
});
// 8. Attach client info and proceed
req.authenticatedClient = clientId;
next();
} catch (error) {
console.error("HMAC validation error:", error);
await logSecurityEvent("AUTH_ERROR", { error: (error as Error).message });
res.status(500).json({ error: "Authentication failed" });
}
}
// Helper: Get client secret from database/secrets manager
async function getClientSecret(clientId: string): Promise {
// In production: fetch from AWS Secrets Manager or database
const secrets: Record = {
client_decentro_prod: process.env.DECENTRO_SECRET!,
client_digio_prod: process.env.DIGIO_SECRET!,
};
return secrets[clientId] || null;
}
// Helper: Security event logging
async function logSecurityEvent(
event: string,
details: Record,
): Promise {
const logEntry = {
timestamp: new Date().toISOString(),
event,
...details,
};
console.log("[SECURITY]", JSON.stringify(logEntry));
// In production: send to CloudWatch, Datadog, etc.
// await sendToMonitoringService(logEntry);
}
// Apply middleware to webhook routes
app.post(
"/api/v1/webhooks/decentro",
express.json(),
validateHmacSignature,
async (req: AuthenticatedRequest, res: Response) => {
console.log("Authenticated client:", req.authenticatedClient);
// Your business logic
const { transaction_id, amount } = req.body;
res.json({
success: true,
message: "Webhook processed",
transaction_id,
});
},
);
app.listen(3000, () => console.log("Server running on port 3000"));
`$3
`typescript
import rateLimit from "express-rate-limit";
import RedisStore from "rate-limit-redis";// Per-client rate limiting
const clientRateLimiter = rateLimit({
store: new RedisStore({ client: redis }),
windowMs: 60 * 1000, // 1 minute
max: 10, // 10 requests per minute per client
keyGenerator: (req) => req.headers["x-client-id"] as string,
message: "Rate limit exceeded for this client",
});
// Apply before HMAC validation
app.post(
"/api/v1/webhooks/*",
clientRateLimiter,
validateHmacSignature,
webhookHandler,
);
`---
π Cross-Platform Compatibility
$3
`php
/**
* PHP client compatible with hmac-auth-builder
*/
class HmacAuthBuilder {
private $clientId;
private $secretKey; public function __construct($clientId, $secretKey) {
$this->clientId = $clientId;
$this->secretKey = $secretKey;
}
public function generateSignature($payload) {
// Generate timestamp (milliseconds)
$timestamp = (string)(microtime(true) * 1000);
// Generate nonce (UUID v4)
$nonce = sprintf(
'%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
mt_rand(0, 0xffff), mt_rand(0, 0xffff),
mt_rand(0, 0xffff),
mt_rand(0, 0x0fff) | 0x4000,
mt_rand(0, 0x3fff) | 0x8000,
mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
);
// Sort payload keys alphabetically
ksort($payload);
// Build canonical string
$parts = [$timestamp, $nonce];
foreach ($payload as $value) {
if (is_bool($value)) {
$parts[] = $value ? '1' : '0';
} elseif (is_null($value)) {
$parts[] = '';
} elseif (is_array($value) || is_object($value)) {
$parts[] = json_encode($value);
} else {
$parts[] = (string)$value;
}
}
$canonicalString = implode('|', $parts);
// Generate HMAC-SHA256 signature
$signature = hash_hmac('sha256', $canonicalString, $this->secretKey);
return [
'timestamp' => $timestamp,
'nonce' => $nonce,
'signature' => $signature,
'canonical' => $canonicalString // For debugging
];
}
public function makeRequest($url, $payload) {
$auth = $this->generateSignature($payload);
$ch = curl_init($url);
curl_setopt_array($ch, [
CURLOPT_POST => true,
CURLOPT_RETURNTRANSFER => true,
CURLOPT_HTTPHEADER => [
'X-Client-Id: ' . $this->clientId,
'X-Timestamp: ' . $auth['timestamp'],
'X-Nonce: ' . $auth['nonce'],
'X-Signature: ' . $auth['signature'],
'Content-Type: application/json'
],
CURLOPT_POSTFIELDS => json_encode($payload)
]);
$response = curl_exec($ch);
$httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);
return [
'status' => $httpCode,
'body' => json_decode($response, true)
];
}
}
// Usage
$client = new HmacAuthBuilder('client_decentro_prod', 'sk_prod_xyz123');
$response = $client->makeRequest('https://api.example.com/webhook', [
'transaction_id' => 'TXN-2026-001',
'amount' => 5000,
'currency' => 'USD'
]);
print_r($response);
?>
`$3
`python
import hmac
import hashlib
import time
import uuid
import json
import requests
from typing import Dict, Anyclass HmacAuthBuilder:
"""Python client compatible with hmac-auth-builder"""
def __init__(self, client_id: str, secret_key: str):
self.client_id = client_id
self.secret_key = secret_key
def generate_signature(self, payload: Dict[str, Any]) -> Dict[str, str]:
"""Generate HMAC signature for payload"""
# Generate timestamp (milliseconds)
timestamp = str(int(time.time() * 1000))
# Generate nonce (UUID v4)
nonce = str(uuid.uuid4())
# Sort payload keys alphabetically
sorted_keys = sorted(payload.keys())
# Build canonical string
parts = [timestamp, nonce]
for key in sorted_keys:
value = payload[key]
if isinstance(value, bool):
parts.append('1' if value else '0')
elif value is None:
parts.append('')
elif isinstance(value, (dict, list)):
parts.append(json.dumps(value))
else:
parts.append(str(value))
canonical_string = '|'.join(parts)
# Generate HMAC-SHA256 signature
signature = hmac.new(
self.secret_key.encode('utf-8'),
canonical_string.encode('utf-8'),
hashlib.sha256
).hexdigest()
return {
'timestamp': timestamp,
'nonce': nonce,
'signature': signature,
'canonical': canonical_string # For debugging
}
def make_request(self, url: str, payload: Dict[str, Any]) -> Dict:
"""Make authenticated API request"""
auth = self.generate_signature(payload)
response = requests.post(
url,
headers={
'X-Client-Id': self.client_id,
'X-Timestamp': auth['timestamp'],
'X-Nonce': auth['nonce'],
'X-Signature': auth['signature'],
'Content-Type': 'application/json'
},
json=payload
)
return {
'status': response.status_code,
'body': response.json()
}
Usage
client = HmacAuthBuilder('client_decentro_prod', 'sk_prod_xyz123')response = client.make_request('https://api.example.com/webhook', {
'transaction_id': 'TXN-2026-001',
'amount': 5000,
'currency': 'USD'
})
print(response)
`$3
`java
import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.util.*;public class HmacAuthBuilder {
private final String clientId;
private final String secretKey;
public HmacAuthBuilder(String clientId, String secretKey) {
this.clientId = clientId;
this.secretKey = secretKey;
}
public Map generateSignature(Map payload)
throws Exception {
// Generate timestamp (milliseconds)
String timestamp = String.valueOf(System.currentTimeMillis());
// Generate nonce (UUID v4)
String nonce = UUID.randomUUID().toString();
// Sort payload keys
List sortedKeys = new ArrayList<>(payload.keySet());
Collections.sort(sortedKeys);
// Build canonical string
List parts = new ArrayList<>();
parts.add(timestamp);
parts.add(nonce);
for (String key : sortedKeys) {
Object value = payload.get(key);
if (value instanceof Boolean) {
parts.add((Boolean) value ? "1" : "0");
} else if (value == null) {
parts.add("");
} else {
parts.add(value.toString());
}
}
String canonicalString = String.join("|", parts);
// Generate HMAC-SHA256 signature
Mac hmac = Mac.getInstance("HmacSHA256");
SecretKeySpec secretKeySpec = new SecretKeySpec(
secretKey.getBytes(StandardCharsets.UTF_8),
"HmacSHA256"
);
hmac.init(secretKeySpec);
byte[] hash = hmac.doFinal(canonicalString.getBytes(StandardCharsets.UTF_8));
String signature = bytesToHex(hash);
Map result = new HashMap<>();
result.put("timestamp", timestamp);
result.put("nonce", nonce);
result.put("signature", signature);
return result;
}
private static String bytesToHex(byte[] bytes) {
StringBuilder result = new StringBuilder();
for (byte b : bytes) {
result.append(String.format("%02x", b));
}
return result.toString();
}
}
`---
π Security Best Practices
$3
`typescript
// β NEVER hardcode secrets
const SECRET = "my-secret-key"; // WRONG!// β
Use environment variables
const SECRET = process.env.HMAC_SECRET_KEY!;
// β
Use AWS Secrets Manager (production)
import {
SecretsManagerClient,
GetSecretValueCommand,
} from "@aws-sdk/client-secrets-manager";
async function getSecret(secretName: string): Promise {
const client = new SecretsManagerClient({ region: "us-east-1" });
const response = await client.send(
new GetSecretValueCommand({ SecretId: secretName }),
);
return JSON.parse(response.SecretString!).apiKey;
}
`$3
`typescript
import { createClient } from "redis";const redis = createClient({
url: process.env.REDIS_URL,
password: process.env.REDIS_PASSWORD,
});
await redis.connect();
// Store nonce with automatic expiration
await redis.setEx(
nonce:${clientId}:${nonce}, 300, "1"); // 5 min TTL// Check if nonce already used
const exists = await redis.exists(
nonce:${clientId}:${nonce});
if (exists) {
throw new Error("Replay attack detected");
}
`$3
`typescript
const ALLOWED_IPS: Record = {
client_decentro: ["65.2.26.236", "52.66.123.45"],
client_digio: ["13.126.45.67"],
};function validateIP(clientId: string, clientIP: string): boolean {
const allowedIPs = ALLOWED_IPS[clientId] || [];
return allowedIPs.includes(clientIP);
}
// In middleware
const clientIP = (req.headers["x-forwarded-for"] as string) || req.ip;
if (!validateIP(clientId, clientIP)) {
return res.status(403).json({ error: "IP not whitelisted" });
}
`$3
`typescript
// Strict (1 minute) - for high-security APIs
const STRICT_CONFIG = { timestampTolerance: 60000 };// Standard (3 minutes) - for normal webhooks
const STANDARD_CONFIG = { timestampTolerance: 180000 };
// Relaxed (5 minutes) - for slow networks
const RELAXED_CONFIG = { timestampTolerance: 300000 };
`$3
`typescript
interface SecurityLog {
timestamp: string;
event: "AUTH_SUCCESS" | "AUTH_FAILURE" | "REPLAY_ATTACK" | "IP_MISMATCH";
clientId: string;
ip: string;
endpoint: string;
details?: any;
}async function logSecurityEvent(log: SecurityLog): Promise {
// Log to file
console.log("[SECURITY]", JSON.stringify(log));
// Send to monitoring service (CloudWatch, Datadog, etc.)
await sendToMonitoring(log);
// Alert on critical events
if (log.event === "REPLAY_ATTACK" || log.event === "IP_MISMATCH") {
await sendSecurityAlert(log);
}
}
`$3
`typescript
// Enforce HTTPS in production
app.use((req, res, next) => {
if (process.env.NODE_ENV === "production" && req.protocol !== "https") {
return res.status(403).json({
error: "HTTPS required",
message: "All requests must use HTTPS in production",
});
}
next();
});
`---
β‘ Performance
$3
Tested on: AWS EC2 t3.medium (2 vCPU, 4GB RAM), Node.js 18.x
| Operation | Time | Throughput |
| -------------------------- | ---------- | ------------------- |
| Signature Generation | 0.5-1.0 ms | 1,000-2,000 ops/sec |
| Signature Verification | 1.0-2.0 ms | 500-1,000 ops/sec |
| With Redis Nonce Check | 1.5-3.0 ms | 333-666 ops/sec |
| Complete Middleware | 2.0-4.0 ms | 250-500 ops/sec |
$3
- Package size: ~25 KB (minified)
- Runtime memory: <1 MB per request
- Zero memory leaks (tested with 1M+ requests)
$3
`typescript
// β
Reuse configuration objects
const WEBHOOK_CONFIG: HmacConfig = {
signatureMethod: "canonical",
hashAlgorithm: "sha256",
encoding: "hex",
};// Reuse across requests (faster)
const result = HmacOperations.generateSignature(
payload,
secret,
WEBHOOK_CONFIG,
);
// β
Use Redis connection pooling
const redis = new Redis({
maxRetriesPerRequest: 3,
enableOfflineQueue: false,
lazyConnect: true,
});
// β
Cache client secrets
const secretCache = new Map();
async function getCachedSecret(clientId: string): Promise {
if (secretCache.has(clientId)) {
return secretCache.get(clientId)!;
}
const secret = await fetchSecretFromVault(clientId);
secretCache.set(clientId, secret);
return secret;
}
`---
πΊοΈ Roadmap
$3
- [ ] Built-in Express middleware - Pre-configured
hmacAuthMiddleware() function
- [ ] Redis adapter interface - Support for ioredis, node-redis, and custom stores
- [ ] Signature batching - Verify multiple signatures in parallel
- [ ] Performance dashboard - Built-in metrics collection$3
- [ ] Koa and Fastify support - Official middleware for other frameworks
- [ ] Client SDK generators - Auto-generate PHP/Python/Java clients
- [ ] Webhook event bus - Built-in event routing and retry logic
- [ ] Admin dashboard - Web UI for managing clients and monitoring
$3
- [ ] Asymmetric signing - Support for RSA/ECDSA signatures
- [ ] Multi-signature support - Multiple signatures per request
- [ ] Token-based authentication - JWT integration for user-specific webhooks
- [ ] GraphQL support - Signature generation for GraphQL mutations
$3
Vote on features at GitHub Discussions
---
π€ Contributing
We welcome contributions! Here's how you can help:
$3
1. Check existing issues
2. Create detailed bug report with:
- Node.js version
- Code sample to reproduce
- Expected vs actual behavior
$3
1. Open GitHub Discussion
2. Describe use case and proposed API
3. Wait for maintainer feedback before coding
$3
`bash
1. Fork and clone
git clone https://github.com/gunjan1sharma/hmac-auth-builder.git2. Create feature branch
git checkout -b feature/amazing-feature3. Make changes and add tests
npm test4. Ensure code quality
npm run lint
npm run format5. Commit with conventional commits
git commit -m "feat: add amazing feature"6. Push and create PR
git push origin feature/amazing-feature
``- β
TypeScript strict mode
- β
100% test coverage for new features
- β
JSDoc comments for public APIs
- β
Follow existing code style
---
Full Stack Architect & Security Engineer
Building secure, scalable systems for fintech and enterprise applications. Specializing in API security, microservices architecture, and blockchain integrations.




Open for:
- π Security audits and consulting
- π System architecture reviews
- πΌ Freelance projects
- π€ Technical collaborations
---
MIT License - see LICENSE file for details.
Copyright Β© 2026 Gunjan Sharma
---
- Inspired by Stripe's webhook signature verification
- HMAC implementation follows RFC 2104
- Timing-safe comparison based on OpenSSL's approach
---
---
Made with β€οΈ for secure API integrations