AES Encryption & Decryption Tool
The Advanced Encryption Standard (AES) is a symmetric-key block cipher adopted by the U.S. government and used worldwide to protect sensitive data. This tool lets you encrypt and decrypt text using AES with multiple key sizes and operation modes — all in your browser, with no data ever sent to a server.
What is AES Encryption?
The Advanced Encryption Standard (AES) is a symmetric-key block cipher adopted by the U.S. National Institute of Standards and Technology (NIST) in 2001. It replaced the aging Digital Encryption Standard (DES) and has become the most widely used encryption algorithm in the world.
AES is a variant of the Rijndael cipher, named after its creators Vincent Rijmen and Joan Daemen. It uses a substitution-permutation network that processes data in fixed-size blocks and repeatedly substitutes and rearranges it to generate ciphertext.
How AES Works
AES operates on fixed 128-bit blocks (16 bytes) of data regardless of the key size. The key size determines the number of encryption rounds:
- AES-128: 10 rounds
- AES-192: 12 rounds
- AES-256: 14 rounds
AES is a symmetric-key algorithm, meaning the same key is used for both encryption and decryption. This makes it fast and efficient for encrypting large amounts of data.
Modes of Operation
AES encrypts data in blocks, but different modes of operation determine how blocks are chained together. Each mode has different security properties and use cases:
| Mode | Description | IV Required | Padding | Use Case |
|---|---|---|---|---|
| ECB | Each block encrypted independently. Identical plaintext blocks produce identical ciphertext. | No | Yes | Not recommended — insecure for most use cases |
| CBC | Each block is XORed with the previous ciphertext block before encryption. | Yes (16 bytes) | Yes | General-purpose encryption (TLS, file encryption) |
| CTR | Converts block cipher into a stream cipher using a counter. No padding required. | Yes (nonce) | No | High-speed encryption, random access |
| CFB | Cipher feedback mode — converts block cipher to stream cipher. | Yes (16 bytes) | No | Streaming data, real-time encryption |
| OFB | Output feedback mode — similar to CFB but with different feedback path. | Yes (16 bytes) | No | Streaming data, error-resistant |
Why Use This Tool?
- Complete Privacy: All encryption happens locally in your browser — no data is ever transmitted.
- Multiple Key Sizes: Support for AES-128, AES-192, and AES-256.
- Multiple Modes: ECB, CBC, CTR, CFB, and OFB modes of operation.
- Custom IV & Salt: Option to provide your own initialization vector and salt.
- Educational: Learn how AES encryption works in practice.
- Free & Open: Completely free to use with no registration required.
Key Security Considerations
- Never use ECB — it's insecure for most applications because identical plaintext blocks produce identical ciphertext.
- Use a unique IV for each encryption operation with the same key. This prevents patterns from emerging in the ciphertext.
- Choose a strong key — AES-256 offers the strongest security.
- Keep your key secret — anyone with the key can decrypt your data.
- Use authenticated encryption (like GCM) in production to ensure both confidentiality and integrity.
❓ AES Encryption Tool FAQ
What is AES encryption?
AES (Advanced Encryption Standard) is a symmetric-key block cipher adopted by the U.S. government in 2001. It is the most widely used encryption standard in the world, securing everything from web traffic to classified government data.
What is the difference between AES-128, AES-192, and AES-256?
The number refers to the key size in bits. AES-128 uses a 128-bit key and 10 rounds, AES-192 uses a 192-bit key and 12 rounds, and AES-256 uses a 256-bit key and 14 rounds. AES-256 offers the strongest security.
What is the difference between ECB, CBC, CTR, CFB, and OFB?
These are modes of operation that determine how blocks are processed. ECB encrypts each block independently (insecure). CBC chains blocks together using an IV. CTR, CFB, and OFB convert the block cipher into a stream cipher, eliminating the need for padding.
What is an Initialization Vector (IV)?
An IV is a random value used to ensure that identical plaintexts encrypt to different ciphertexts. It's required for CBC, CFB, and OFB modes. The IV does not need to be secret but must be unique for each encryption with the same key.
Is my data safe when using this tool?
Yes! All encryption and decryption operations are performed entirely in your browser using CryptoJS. Your data never leaves your device — no information is sent to any server.
What is the recommended AES mode for general use?
CBC (Cipher Block Chaining) is the most widely recommended mode for general-purpose encryption. It provides good security when used with a random IV and proper padding. GCM (Galois/Counter Mode) is recommended for authenticated encryption in production systems.
Why shouldn't I use ECB mode?
ECB mode encrypts each block independently, meaning identical plaintext blocks produce identical ciphertext blocks. This reveals patterns in the data and is insecure for most applications. Only use ECB for single-block encryption or test vectors.
How do I decrypt a message encrypted with this tool?
Select "Decrypt" as the operation, enter the ciphertext in the input field, and provide the same key, key size, mode, and IV that were used for encryption. The tool will recover the original plaintext.
What is the difference between symmetric and asymmetric encryption?
Symmetric encryption (like AES) uses the same key for both encryption and decryption. Asymmetric encryption uses a public key for encryption and a private key for decryption. AES is much faster than asymmetric encryption and is used for bulk data encryption.
Is AES still considered secure in 2026?
Yes, AES remains highly secure. Even AES-128 is considered secure against conventional computers — it would take the world's fastest supercomputer trillions of years to brute force it. AES-256 provides an additional margin of security against future quantum threats.