npm package: @systemix/token
Description: A cryptographically secure token generator and signed-token module for API keys, session tokens, and auth. Zero dependencies, pure Node.js.
Author: Shahadath Hossen Sajib
Latest version: 1.4.0

# @systemix/token

[![npm](https://img.shields.io/npm/v/@systemix/token.svg)](https://www.npmjs.com/package/@systemix/token)

A cryptographically secure token generator and signed-token module for API keys, session tokens, CSRF tokens, and auth. Zero external dependencies, pure Node.js and browser built-ins.

---

## Table of Contents

- [Features](#features)
- [Installation](#installation)
- [Package Structure](#package-structure)
- [Token Generator](#token-generator)
- [Signed Tokens](#signed-tokens)
- [RSA Module](#rsa-module)
- [Common Module (Internals)](#common-module-internals)
- [Error Handling](#error-handling)
- [Usage Examples](#usage-examples)
- [Security Notes](#security-notes)
- [API Reference](#api-reference)

---

## Features

- **Secure**: Uses `crypto.getRandomValues()` for cryptographically strong randomness.
- **Multiple Charsets**: Hex, base64, base64url (URL-safe), and alphanumeric.
- **Signed Tokens**: HMAC (HS256/384/512) and RSA (RS256/384/512) with standard claims.
- **Subpath Exports**: Import only what you need (`/token`, `/signed`, `/rsa`, `/common`).
- **Zero Dependencies**: Built with Node.js/browser built-ins only.
- **TypeScript Ready**: Full type definitions included.

---

## Installation

```bash
pnpm add @systemix/token
```

```bash
npm install @systemix/token
```

---

## Package Structure

| Subpath                  | Contents                                           |
| :----------------------- | :------------------------------------------------- |
| `@systemix/token`        | Main entry — re-exports token, signed, rsa, common |
| `@systemix/token/token`  | Token generator, encoding utils, validation        |
| `@systemix/token/signed` | Signed token encode/decode/verify                  |
| `@systemix/token/rsa`    | RSA sign/verify (Node + browser, auto-detect)      |
| `@systemix/token/common` | Crypto, enums, types, errors, utils                |

---

## Token Generator

### `generateToken(props?)`

Generates cryptographically secure random tokens. Returns a single string or array of strings.

```typescript
import { generateToken } from '@systemix/token';

// Default: 32 bytes, hex encoding
const token = generateToken();
// → "a1b2c3d4e5f6789..."

// With options
const apiKey = generateToken({
  byteLength: 32,
  charset: 'hex',
});

const sessionToken = generateToken({
  byteLength: 24,
  charset: 'base64url', // URL-safe, no + or /
});

const batch = generateToken({
  byteLength: 16,
  charset: 'alphanumeric',
  count: 5,
});
// → ["Ab3xYz...", "Mn7pQr...", ...]
```

#### Props

| Property     | Type                                                 | Default | Description                                                        |
| :----------- | :--------------------------------------------------- | :------ | :----------------------------------------------------------------- |
| `byteLength` | `number`                                             | `32`    | Number of random bytes (1–1024). Output length depends on charset. |
| `charset`    | `'hex' \| 'base64' \| 'base64url' \| 'alphanumeric'` | `'hex'` | Encoding format.                                                   |
| `count`      | `number`                                             | `1`     | Number of tokens to generate (1–10). Returns `string[]` when > 1.  |

#### Charset behavior

| Charset        | Output length                 | Use case                         |
| :------------- | :---------------------------- | :------------------------------- |
| `hex`          | `byteLength × 2`              | API keys, opaque IDs             |
| `base64`       | ~`byteLength × 4/3`           | Compact tokens                   |
| `base64url`    | ~`byteLength × 4/3`, URL-safe | URLs, cookies                    |
| `alphanumeric` | `byteLength`                  | Human-readable, no special chars |

---

### `generateTokenPropValidation(props)`

Validates props before generation. Throws if invalid. Useful when building custom flows.

```typescript
import { generateTokenPropValidation } from '@systemix/token/token';

try {
  generateTokenPropValidation({ byteLength: 64, charset: 'hex' });
  // proceed with generation
} catch (e) {
  console.error(e.message);
}
```

---

### Encoding utilities

Use these when you need to encode raw bytes yourself:

```typescript
import {
  bytesToHex,
  bytesToBase64,
  bytesToBase64Url,
  bytesToAlphanumeric,
} from '@systemix/token/token';

const bytes = new Uint8Array([0x48, 0x65, 0x6c, 0x6c, 0x6f]);

bytesToHex(bytes); // → "48656c6c6f"
bytesToBase64(bytes); // → "SGVsbG8="
bytesToBase64Url(bytes); // → "SGVsbG8" (no padding)
bytesToAlphanumeric(bytes); // → "NkF2bB2" (A–Z, a–z, 0–9)
```

| Function                     | Input        | Output          |
| :--------------------------- | :----------- | :-------------- |
| `bytesToHex(bytes)`          | `Uint8Array` | Hex string      |
| `bytesToBase64(bytes)`       | `Uint8Array` | Base64 string   |
| `bytesToBase64Url(bytes)`    | `Uint8Array` | URL-safe base64 |
| `bytesToAlphanumeric(bytes)` | `Uint8Array` | A–Z, a–z, 0–9   |

---

### Token enums and types

```typescript
import { CHARSETS, TokenPropsEnum, type Charset } from '@systemix/token/token';
import type { GenerateTokenFunctionProps } from '@systemix/token/token';

// CHARSETS: ['hex', 'base64', 'base64url', 'alphanumeric']
// Charset: 'hex' | 'base64' | 'base64url' | 'alphanumeric'
// TokenPropsEnum: BYTE_LENGTH, CHARSET, COUNT
```

---

## Signed Tokens

Signed tokens are compact, URL-safe strings with a header, payload, and signature. Use for auth, sessions, or any signed claims. **HMAC and RSA work in both Node and browser** (Web Crypto API; RSA auto-detects environment).

### `encodeSigned(payload, secret, options?)`

Creates a signed token. Returns `Promise<string>`. Supports HMAC (shared secret) and RSA (PEM private key).

```typescript
import { encodeSigned } from '@systemix/token/signed';

// HMAC (shared secret) — works in browser and Node
const token = await encodeSigned(
  { userId: '123', role: 'admin' },
  'my-secret-key',
  {
    algorithm: 'HS256',
    expiresIn: 3600,
    issuer: 'my-app',
    audience: 'api',
    subject: 'user-123',
    tokenId: true, // auto-generate jti
  },
);

// RSA (PEM private key) — Node.js only
const tokenRsa = await encodeSigned({ userId: '123' }, privateKeyPem, {
  algorithm: 'RS256',
  expiresIn: 3600,
});
```

#### Encode options

| Option      | Type                 | Default   | Description                          |
| :---------- | :------------------- | :-------- | :----------------------------------- |
| `algorithm` | `SignedAlgorithm`    | `'HS256'` | Signing algorithm.                   |
| `typ`       | `string`             | `'ST'`    | Token type in header.                |
| `kid`       | `string`             | —         | Key ID for key rotation.             |
| `cty`       | `string`             | —         | Content type.                        |
| `expiresIn` | `number`             | —         | Expiration in seconds from now.      |
| `notBefore` | `number`             | —         | Not-before in seconds from now.      |
| `issuedAt`  | `number`             | `now`     | Issued-at timestamp.                 |
| `issuer`    | `string`             | —         | `iss` claim.                         |
| `subject`   | `string`             | —         | `sub` claim.                         |
| `audience`  | `string \| string[]` | —         | `aud` claim.                         |
| `tokenId`   | `string \| true`     | —         | `jti` claim. `true` = auto-generate. |

---

### `decodeSigned(token)`

Decodes a token **without** verifying the signature. Use when you need to inspect header/payload before deciding whether to verify.

```typescript
import { decodeSigned } from '@systemix/token/signed';

const { header, payload, signature } = decodeSigned<{ userId: string }>(token);

console.log(header.alg); // "HS256"
console.log(payload.userId); // "123"
```

Returns `DecodedToken<T>`:

```typescript
interface DecodedToken<T> {
  header: SignedHeader;
  payload: T;
  signature: string;
}
```

---

### `verifySigned(token, secret, options)`

Decodes and verifies a token. Validates signature and optional claims. **`algorithms` is required** to prevent algorithm confusion.

```typescript
import { verifySigned } from '@systemix/token/signed';

const payload = await verifySigned<{ userId: string }>(token, 'my-secret', {
  algorithms: ['HS256'],
  issuer: 'my-app',
  audience: 'api',
  subject: 'user-123',
  clockTolerance: 60, // 60s skew for exp/nbf
});
```

#### Verify options

| Option             | Type                 | Required | Description                                          |
| :----------------- | :------------------- | :------- | :--------------------------------------------------- |
| `algorithms`       | `SignedAlgorithm[]`  | **Yes**  | Allowed algorithms. Prevents algorithm-swap attacks. |
| `issuer`           | `string \| string[]` | No       | Expected `iss`.                                      |
| `audience`         | `string \| string[]` | No       | Expected `aud`.                                      |
| `subject`          | `string`             | No       | Expected `sub`.                                      |
| `clockTolerance`   | `number`             | No       | Seconds of skew for `exp`/`nbf`.                     |
| `ignoreExpiration` | `boolean`            | No       | Skip `exp` check.                                    |
| `ignoreNotBefore`  | `boolean`            | No       | Skip `nbf` check.                                    |

---

### Algorithms

| Algorithm           | Type             | Secret / key                                      |
| :------------------ | :--------------- | :------------------------------------------------ |
| HS256, HS384, HS512 | HMAC (symmetric) | Shared secret string                              |
| RS256, RS384, RS512 | RSA (asymmetric) | PEM private key (encode), PEM public key (verify) |

```typescript
import {
  HMAC_ALGORITHMS,
  RSA_ALGORITHMS,
  type SignedAlgorithm,
  type HmacAlgorithm,
  type RsaAlgorithm,
} from '@systemix/token/common';
```

---

### Standard claims

| Claim | Type                 | Description               |
| :---- | :------------------- | :------------------------ |
| `iss` | `string`             | Issuer                    |
| `sub` | `string`             | Subject                   |
| `aud` | `string \| string[]` | Audience                  |
| `exp` | `number`             | Expiration (Unix seconds) |
| `nbf` | `number`             | Not before (Unix seconds) |
| `iat` | `number`             | Issued at (Unix seconds)  |
| `jti` | `string`             | Token ID                  |

---

### Signed token types

```typescript
import type {
  SignedHeader,
  SignedPayload,
  EncodeSignedOptions,
  VerifySignedOptions,
  DecodedToken,
  StandardClaims,
} from '@systemix/token/signed';
```

---

## Shared Utilities

Low-level crypto primitives. Use when building custom token logic.

```typescript
import { getRandomBytes, getRandomInt } from '@systemix/token/common';

// Cryptographically secure random bytes
const bytes = getRandomBytes(32);

// Random integer in [0, max)
const n = getRandomInt(100);
```

| Function                 | Description                                    |
| :----------------------- | :--------------------------------------------- |
| `getRandomBytes(length)` | Returns `Uint8Array` of random bytes.          |
| `getRandomInt(max)`      | Returns random integer in `[0, max)`.          |
| `bytesEqual(a, b)`       | Constant-time byte comparison (timing-safe).   |
| `secureCompare(a, b)`    | Constant-time string comparison (timing-safe). |

---

## Common Module (Internals)

For advanced use: enums, types, errors, and encoding utils.

```typescript
import {
  // Enums
  CHARSETS,
  HMAC_ALGORITHMS,
  RSA_ALGORITHMS,
  TokenPropsEnum,
  ALG_TO_HASH,
  isHmac,
  isRsa,
  // Types
  type Charset,
  type SignedAlgorithm,
  type HmacAlgorithm,
  type RsaAlgorithm,
  type GenerateTokenFunctionProps,
  type SignedHeader,
  type SignedPayload,
  type StandardClaims,
  // Errors
  SignedTokenError,
  TokenExpiredError,
  NotBeforeError,
  InvalidSignatureError,
  InvalidTokenError,
  AudienceMismatchError,
  IssuerMismatchError,
  // Utils
  bytesToHex,
  bytesToBase64,
  bytesToBase64Url,
  bytesToAlphanumeric,
  base64UrlEncode,
  base64UrlDecode,
  base64UrlDecodeToUtf8,
} from '@systemix/token/common';
```

---

## Error Handling

### Token generator errors

`generateToken` and `generateTokenPropValidation` throw generic `Error` with messages such as:

- `Invalid byteLength. Must be a positive number.`
- `Invalid charset. Must be one of: hex, base64, base64url, alphanumeric.`
- `Invalid count. Count must be less than or equal to 10.`
- `Invalid prop(s): foo. Only the following options are allowed: byteLength, charset, count.`

### Signed token errors

All extend `SignedTokenError`:

| Error                   | When                                                    |
| :---------------------- | :------------------------------------------------------ |
| `InvalidTokenError`     | Malformed token, invalid encoding, missing alg          |
| `InvalidSignatureError` | Signature mismatch, wrong secret, algorithm not allowed |
| `TokenExpiredError`     | `exp` in the past                                       |
| `NotBeforeError`        | `nbf` in the future                                     |
| `AudienceMismatchError` | `aud` does not match                                    |
| `IssuerMismatchError`   | `iss` does not match                                    |

```typescript
import {
  verifySigned,
  TokenExpiredError,
  InvalidSignatureError,
} from '@systemix/token/signed';

try {
  const payload = await verifySigned(token, secret, { algorithms: ['HS256'] });
} catch (e) {
  if (e instanceof TokenExpiredError) {
    console.log('Expired at', e.expiredAt);
  } else if (e instanceof InvalidSignatureError) {
    console.log('Invalid signature');
  }
}
```

---

## Usage Examples

### API key generation

```typescript
import { generateToken } from '@systemix/token';

const apiKey = generateToken({
  byteLength: 32,
  charset: 'hex',
});
// Store hashed in DB, return plain once to user
```

### Session token with signed payload

```typescript
import { encodeSigned, verifySigned } from '@systemix/token/signed';

// On login
const sessionToken = await encodeSigned(
  { userId: user.id, email: user.email },
  process.env.SESSION_SECRET!,
  { expiresIn: 86400, issuer: 'my-app' },
);

// On request
const payload = await verifySigned(sessionToken, process.env.SESSION_SECRET!, {
  algorithms: ['HS256'],
  issuer: 'my-app',
});
```

### RSA for distributed verification

```typescript
import { encodeSigned, verifySigned } from '@systemix/token/signed';
import { readFileSync } from 'fs';

const privateKey = readFileSync('private.pem', 'utf8');
const publicKey = readFileSync('public.pem', 'utf8');

const token = await encodeSigned({ sub: 'user-1' }, privateKey, {
  algorithm: 'RS256',
  expiresIn: 3600,
});

// Any service with public key can verify
const payload = await verifySigned(token, publicKey, {
  algorithms: ['RS256'],
});
```

### Custom encoding pipeline

```typescript
import { getRandomBytes } from '@systemix/token/common';
import { bytesToBase64Url } from '@systemix/token/common';

const bytes = getRandomBytes(24);
const token = bytesToBase64Url(bytes);
```

---

## Security Notes

- **Algorithm whitelist**: Always pass `algorithms` to `verifySigned`. Never trust the token header.
- **Secret strength**: Use at least 256 bits (32 bytes) for HMAC secrets.
- **RSA keys**: Use 2048+ bit keys. Keep the private key secret.
- **Clock skew**: Use `clockTolerance` when servers may have time drift.
- **Sensitive data**: Signed tokens are signed, not encrypted. Do not put secrets in the payload.

---

## API Reference

### Main exports (`@systemix/token`)

Re-exports everything from `/token`, `/signed`, `/rsa`, and `/common`.

### Token (`@systemix/token/token`)

- `generateToken(props?)` → `string | string[]`
- `generateTokenPropValidation(props)` → `void`
- `bytesToHex`, `bytesToBase64`, `bytesToBase64Url`, `bytesToAlphanumeric`
- `CHARSETS`, `TokenPropsEnum`, `Charset`, `GenerateTokenFunctionProps`

### Signed (`@systemix/token/signed`)

- `encodeSigned(payload, secret, options?)` → `Promise<string>`
- `decodeSigned(token)` → `DecodedToken<T>`
- `verifySigned(token, secret, options)` → `Promise<T>`
- Types: `SignedHeader`, `SignedPayload`, `EncodeSignedOptions`, `VerifySignedOptions`, `DecodedToken`, `StandardClaims`
- Algorithms: `SignedAlgorithm`, `HmacAlgorithm`, `RsaAlgorithm`
- Errors: `SignedTokenError`, `TokenExpiredError`, `NotBeforeError`, `InvalidSignatureError`, `InvalidTokenError`, `AudienceMismatchError`, `IssuerMismatchError`

### RSA (`@systemix/token/rsa`)

Direct RSA sign/verify for custom formats. Auto-detects Node vs browser.

```typescript
import { signRsa, verifyRsa } from '@systemix/token/rsa';

const sig = await signRsa('data', privateKeyPem, 'RS256');
const valid = await verifyRsa('data', sig, publicKeyPem, 'RS256');
```

### Common (`@systemix/token/common`)

- `getRandomBytes(length)` → `Uint8Array`
- `getRandomInt(max)` → `number`
- `bytesEqual(a, b)` → `boolean` (constant-time)
- `secureCompare(a, b)` → `boolean` (constant-time)
- Enums: `CHARSETS`, `HMAC_ALGORITHMS`, `RSA_ALGORITHMS`, `TokenPropsEnum`, `HMAC_WEB_CRYPTO_HASH`, `RSA_NODE_HASH`, `isHmac`, `isRsa`
- Types: `Charset`, `SignedAlgorithm`, `HmacAlgorithm`, `RsaAlgorithm`, `GenerateTokenFunctionProps`, `SignedHeader`, `SignedPayload`, `StandardClaims`, etc.
- Errors: All signed token error classes
- Utils: `bytesToHex`, `bytesToBase64`, `bytesToBase64Url`, `bytesToAlphanumeric`, `base64UrlEncode`, `base64UrlDecode`, `base64UrlDecodeToUtf8`

---

## License

MIT © [shahadathhs](https://github.com/shahadathhs)