rn-pdf-decrypt

React Native compatible PDF decryption with AES-256 and RC4 support. Fork of @pdfsmaller/pdf-decrypt that replaces Web Crypto API with @noble/hashes + @noble/ciphers for Hermes compatibility.

Why this fork?

The original @pdfsmaller/pdf-decrypt uses crypto.subtle (Web Crypto API), which is not available in React Native's Hermes engine. This fork swaps in pure JS crypto from the audited @noble libraries, making it work in React Native, Hermes, browsers, Node.js 18+, and Deno.

Additionally, this fork adds support for AES-256 V=5/R=5 (Adobe's pre-ISO extension used by Acrobat X/XI), which the upstream package does not support.

Features

• AES-256 decryption (V=5, R=5/6) — PDF 2.0 standard + Adobe extension
• RC4 40/128-bit decryption (V=1-2, R=2-3) — legacy support
• User + Owner passwords — accepts either password to decrypt
• React Native / Hermes compatible — no Web Crypto API dependency
• Pure JS crypto — @noble/hashes + @noble/ciphers (audited, zero-dep)
• Lightweight — ~18KB total (crypto + decryption logic)
• TypeScript types included

Installation

npm install rn-pdf-decrypt pdf-lib

Quick Start

import { decryptPDF } from 'rn-pdf-decrypt';
import fs from 'fs';

const pdfBytes = fs.readFileSync('encrypted.pdf');
const decrypted = await decryptPDF(new Uint8Array(pdfBytes), 'my-password');
fs.writeFileSync('decrypted.pdf', decrypted);

API

decryptPDF(pdfBytes, password)

Decrypt a password-protected PDF. Supports both AES-256 and RC4 encryption — the algorithm is detected automatically.

| Parameter | Type | Description | |-----------|------|-------------| | pdfBytes | Uint8Array | The encrypted PDF file as bytes | | password | string | The user or owner password |

Returns: Promise<Uint8Array> — The decrypted PDF bytes

Throws:

• "This PDF is not encrypted" — if the PDF has no encryption dictionary
• "Incorrect password" — if neither user nor owner password matches
• "Unsupported encryption" — if the encryption version is not supported

isEncrypted(pdfBytes)

Check if a PDF is encrypted without attempting to decrypt it.

| Parameter | Type | Description | |-----------|------|-------------| | pdfBytes | Uint8Array | The PDF file as bytes |

Returns: Promise<{ encrypted: boolean, algorithm?: 'AES-256' | 'RC4', version?: number, revision?: number, keyLength?: number }>

Examples

Decrypt with Auto-Detection

import { decryptPDF, isEncrypted } from 'rn-pdf-decrypt';

// Check encryption type first
const info = await isEncrypted(pdfBytes);
if (info.encrypted) {
  console.log(`Encrypted with ${info.algorithm}`);
  const decrypted = await decryptPDF(pdfBytes, password);
}

React Native Usage

import { decryptPDF } from 'rn-pdf-decrypt';
import RNFS from 'react-native-fs';

const base64 = await RNFS.readFile(filePath, 'base64');
const pdfBytes = Uint8Array.from(atob(base64), c => c.charCodeAt(0));

const decrypted = await decryptPDF(pdfBytes, 'my-password');

Supported Encryption

| Algorithm | PDF Version | Key Length | Status | |-----------|-------------|-----------|--------| | AES-256 (V=5, R=6) | 2.0 (ISO 32000-2) | 256-bit | Supported | | AES-256 (V=5, R=5) | Adobe Extension Level 3 | 256-bit | Supported | | RC4 (V=2, R=3) | 1.4+ (ISO 32000-1) | 128-bit | Supported | | RC4 (V=1, R=2) | 1.1+ | 40-bit | Supported | | AES-128 (V=4, R=4) | 1.6+ | 128-bit | Not yet supported |

Differences from upstream

| | @pdfsmaller/pdf-decrypt | rn-pdf-decrypt | |---|---|---| | Crypto backend | Web Crypto API (crypto.subtle) | @noble/hashes + @noble/ciphers | | React Native | No (Hermes lacks Web Crypto) | Yes | | AES-256 V=5/R=5 | No | Yes | | Dependencies | Zero (peer: pdf-lib) | @noble/hashes, @noble/ciphers (peer: pdf-lib) |

License

MIT

Based on @pdfsmaller/pdf-decrypt by PDFSmaller.com.