AES Encryption & Decryption Online (128/256-bit)

Secure online Advanced Encryption Standard (AES) calculator supporting CBC, GCM, CTR modes with cryptographic key generation and authentication tags.

Deep-Dive Educational Guide

AES-256 Block Cipher: Galois Fields GF(2⁸), Substitution-Permutation Networks & Modern Modes

An exhaustive academic breakdown of the Advanced Encryption Standard (Rijndael): Substitution-Permutation Networks, finite field arithmetic in GF(2⁸), SubBytes S-Box inversion, ShiftRows and MixColumns diffusion, Key Expansion, block cipher modes (ECB, CBC, CTR, GCM), and runnable Python implementations.

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How to Use AES Encryption & Decryption Online (128/256-bit)

  1. Input Text or Hex Payload: Paste your plaintext message or hexadecimal ciphertext into the input panel.
  2. Select Key Size (128, 192, 256) & Mode: Choose AES-128, AES-192, or AES-256 and select an operational mode like GCM (authenticated) or CBC.
  3. Generate or Input Key & IV: Provide your secret key and Initialization Vector (IV/Nonce), or use the built-in cryptographically secure generator.

Frequently Asked Questions

What is AES (Advanced Encryption Standard)?

AES is a symmetric block cipher established by the U.S. NIST in 2001. It processes 128-bit blocks of data using cryptographic keys of 128, 192, or 256 bits and is the global standard for secure encryption.

What is the difference between AES-GCM and AES-CBC?

AES-CBC provides confidentiality but requires padding and a separate HMAC for integrity. AES-GCM provides Authenticated Encryption with Associated Data (AEAD), combining high-performance encryption and message authentication in one pass.

Why is an Initialization Vector (IV) required?

An IV ensures that identical plaintexts encrypted with the same key produce completely unique ciphertexts, preventing pattern leakage and replay attacks.