DiffCheck

AES 暗号化/復号オンライン

ブラウザ上でAES-128/192/256-GCMによるテキストの暗号化・復号を行います。データはデバイス外に送信されません。

鍵長:

すべての処理はWeb Crypto APIを使用してブラウザ上で完結します。データはサーバーに送信されません。

出力形式：16バイトsalt + 12バイトIV + 暗号文、Base64エンコード。PBKDF2 SHA-256、10万回反復。

What Is the AES Encrypt & Decrypt Tool?

This AES encryption tool lets you encrypt and decrypt text directly in your browser using the Web Crypto API — no server, no data leaks. It supports AES-128, AES-192, and AES-256 in GCM mode (authenticated encryption), which is the recommended standard for secure symmetric encryption.

The key is derived from your password using PBKDF2 with 100,000 iterations and SHA-256, and a random 16-byte salt is generated for each encryption. The 12-byte GCM IV is also randomly generated. Both are stored in the ciphertext output so decryption only needs the same password.

How to Use the AES Encryption Tool

  1. Select Encrypt or Decrypt mode.
  2. Choose your key size: AES-128, AES-192, or AES-256 (256-bit recommended).
  3. Enter your password — this is used to derive the encryption key.
  4. Paste or type the text to encrypt (or the Base64 ciphertext to decrypt).
  5. Click Encrypt (or Decrypt). The result appears instantly.
  6. Use the Swap to Decrypt button to flip the output back into the input for quick round-trip testing.

Features

  • Runs 100% in the browser — no network requests, no data logging
  • AES-GCM authenticated encryption (detects tampering)
  • Key sizes: AES-128, AES-192, AES-256
  • Password-based key derivation via PBKDF2 (SHA-256, 100k iterations)
  • Random salt and IV per encryption for cryptographic uniqueness
  • Base64-encoded output — safe to paste anywhere
  • One-click copy and swap-to-decrypt shortcut

FAQ

Is my data safe when using this AES tool?

Yes. All encryption and decryption runs entirely in your browser using the Web Crypto API. No text or password is ever sent to any server. You can use this tool offline after the page loads.

What is AES-GCM and why is it used here?

AES-GCM (Galois/Counter Mode) is an authenticated encryption mode that provides both confidentiality and data integrity. Unlike AES-CBC, GCM detects if the ciphertext has been tampered with, making it the recommended choice for modern applications.

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

The number refers to the key length in bits. AES-256 provides the highest security margin and is recommended for sensitive data. AES-128 is still considered secure for most use cases. All three use the same algorithm — only the key size differs.

Can I decrypt the output on another system?

The output format is: 16-byte PBKDF2 salt + 12-byte GCM IV + ciphertext, Base64-encoded. Any system that supports PBKDF2 (SHA-256, 100,000 iterations) and AES-GCM can decrypt it with the same password and key size.