ToolMight LogoToolMight

AES Encryption & Decryption

Encrypt and decrypt text data using AES-128, AES-192, and AES-256 (CBC/GCM modes) locally in your browser. Web Crypto API zero-trust security tool.

Loading Tool...

Encrypt and decrypt sensitive text messages, credentials, and payload strings using industry-standard AES-256 (GCM or CBC modes). Powered by the browser-native Web Cryptography API with PBKDF2 key derivation and zero server tracking.

Learn About This Tool

Advanced Encryption Standard (AES-256) Specifications & Cryptography

The Advanced Encryption Standard (AES) is a symmetric block cipher algorithm established by the U.S. National Institute of Standards and Technology (NIST) in 2001. AES-256 utilizes a 256-bit key length and 14 transformation rounds, making it mathematically immune to brute-force attacks with current and foreseeable computing hardware. Symmetric encryption means the exact same secret passphrase is required for both encryption and decryption operations.
// Encrypted Cipher Bundle Structure:
// [Derived Salt (16 bytes)][Initialization Vector (12/16 bytes)][Ciphertext Payload]

// Output Base64 Format Example:
U2FsdGVkX1948293ad9871a2bc4e5f6...
  • 256-bit key length with 14 substitution-permutation round transformations
  • PBKDF2 key derivation using 100,000 iterations of SHA-256 for passphrase hardening
  • Cryptographically secure pseudo-random Initialization Vector (IV) generation
  • Output bundle formats encoded in Base64 or Hexadecimal strings

Comparing Cipher Modes: AES-256-GCM vs AES-256-CBC

Selecting the appropriate block cipher mode is critical for application security. AES-GCM (Galois/Counter Mode) is an Authenticated Encryption with Associated Data (AEAD) mode that guarantees both confidentiality and data integrity. If an attacker tampers with a single bit of GCM ciphertext, decryption fails immediately. AES-CBC (Cipher Block Chaining) is a legacy mode providing confidentiality only, requiring PKCS#7 padding.
  • AES-GCM mode: Provides AEAD message integrity verification to prevent bit-flipping attacks
  • AES-CBC mode: Standard block chaining mode requiring initialization vector (IV) prepending
  • Unique IV generation per request prevents identical plaintexts from producing matching ciphertexts
  • Automatic PBKDF2 salt derivation protects against precomputed rainbow table attacks

Browser-Native Web Cryptography API (`window.crypto.subtle`)

Unlike legacy web utilities that rely on third-party JavaScript libraries, this tool executes using the browser's hardware-accelerated Web Cryptography API (window.crypto.subtle). For cryptographic hashing checks like SHA-256 or MD5 without secret keys, try our Hash Generator. To inspect Base64 structures, check our Base64 Encoder / Decoder.
  • Hardware-accelerated native browser cryptography execution
  • Secret passphrases never cross HTTP network connections
  • Derived key data stays strictly inside non-exportable browser memory
  • Handles payload encryption client-side with zero network latency

Security Best Practices for Key Management & Storage

AES-256 encryption is mathematically uncrackable when strong passphrases are used. However, system security relies on proper key distribution and storage. Passphrases should contain at least 16 random characters (combining uppercase, lowercase, numbers, and symbols). Never hardcode passphrases directly into frontend code repositories.
  • Use strong passphrases generated by cryptographically secure generators
  • Store encryption keys in environment variables or secure key vaults
  • Always verify GCM authentication tags when consuming incoming payloads
  • Rotate encryption keys periodically in production systems

How to Use AES Encryption & Decryption

1

Select Mode & Enter Secret Passphrase

Choose `Encrypt` or `Decrypt` mode, select your preferred cipher algorithm (GCM or CBC), and type your secret passphrase in the key field.

2

Input Payload Text

In Encrypt mode, paste your plaintext message. In Decrypt mode, paste the Base64 or Hex ciphertext bundle string.

3

Execute & Copy Result

Click `Process Payload` to execute the Web Cryptography cipher. Click `Copy` to grab the encrypted ciphertext or decrypted message.

Common questions

Is AES-256 encryption secure?

Yes. AES-256 is the cryptographic standard mandated by NIST and approved globally for securing sensitive government, military, and financial communications.

What is an Initialization Vector (IV)?

An IV is a cryptographically random data block that seeds the cipher. It ensures that encrypting the same text twice with the same passphrase produces entirely different ciphertexts.

How does the tool bundle the salt and IV?

To allow seamless decryption later, the output string combines the randomly generated Salt (16 bytes), IV (12 or 16 bytes), and Ciphertext into a unified Base64 or Hex string.

Why does decryption fail when using the correct passphrase?

Ensure that the Algorithm Mode (GCM vs CBC) and Format (Base64 vs Hex) match the exact settings selected during encryption. Any mismatch causes decryption to fail.

What is PBKDF2 key derivation?

PBKDF2 (Password-Based Key Derivation Function 2) applies 100,000 iterations of SHA-256 to stretch your text passphrase into a secure 256-bit binary encryption key.

Are my passphrases or data sent to external servers?

No. All cryptographic operations run 100% locally in your browser using the native Web Cryptography API (`window.crypto.subtle`).

What is the difference between AES-128, AES-192, and AES-256?

AES-256 uses a 256-bit key length with 14 rounds, providing maximum computational resistance against quantum and brute-force attacks compared to 128-bit or 192-bit keys.

Why is GCM mode preferred over CBC mode?

AES-GCM provides Authenticated Encryption (AEAD). It verifies that the payload has not been modified or tampered with, whereas CBC only provides confidentiality and is susceptible to padding oracle attacks if unauthenticated.

Can I recover encrypted data if I lose my passphrase?

No. AES-256 is a mathematically secure standard with no backdoors. If the secret passphrase is lost, the encrypted data cannot be recovered.

Is there a limit to the size of the text I can encrypt?

The Web Cryptography API handles text files and payloads up to 50MB smoothly inside browser memory.

What is the difference between Base64 and Hexadecimal output encoding?

Base64 uses 64 characters to represent binary data in a shorter string format, while Hexadecimal uses 16 characters (0-9, a-f) resulting in slightly longer strings. Both represent identical binary cipher data.

Can I use AES-256 to encrypt JSON API payloads?

Yes! You can stringify any JSON object and encrypt it with AES-256 to securely transmit sensitive payloads over untrusted networks.

Is this tool compatible with Node.js crypto module?

Yes. The PBKDF2 salt, IV, and AES parameters match Node.js `crypto.createCipheriv()` standards.

Are there keyboard shortcuts?

Press `Ctrl+L` (or `Cmd+L` on Mac) to reset all fields instantly.

Related tools

RSA Key Generator

New

Build secure RSA public and private key pairs.

Password Generator

New

Create strong random passwords and check strength.

JWT Creator & Signer

Generate and sign custom JWT tokens securely in the browser.

UUID Generator

Popular

Generate secure bulk v1, v4, and v7 UUIDs.

Deep Dives & Guides

Master this tool with our expert tutorials and best practices.

2 min readArticle

In-Browser Cryptography: Implementing AES-GCM Encryption with Web Crypto API

Learn how to use native W3C Web Cryptography APIs (crypto.subtle) in JavaScript to encrypt sensitive data client-side with AES-256-GCM, PBKDF2 key derivation, and RSA-OAEP.

Read Full Guide