🔒AES Encryption
Encrypt and decrypt text using AES-256 symmetric encryption.
What Is AES Encryption?
AES (Advanced Encryption Standard) is a symmetric block cipher adopted by the U.S. National Institute of Standards and Technology (NIST) in 2001 after a five-year public competition. It replaced the older DES (Data Encryption Standard) and has become the most widely used encryption algorithm in the world. AES encrypts data in fixed 128-bit blocks using keys of 128, 192, or 256 bits.
The term "symmetric" means the same key is used for both encryption and decryption. This makes AES extremely fast compared to asymmetric algorithms like RSA, but it also means both parties must securely share the key beforehand.
How Does AES-256 Work?
AES-256 processes data through 14 rounds of transformation, each consisting of four steps:
- SubBytes: Each byte of the block is substituted using a fixed lookup table (S-box), providing non-linearity.
- ShiftRows: Rows of the 4×4 byte matrix are cyclically shifted to diffuse data across columns.
- MixColumns: Columns are mixed using matrix multiplication in a Galois field, further spreading each byte's influence.
- AddRoundKey: The block is XORed with a round-specific sub-key derived from the original 256-bit key.
The Key is the 256-bit secret used to encrypt and decrypt. The IV (Initialization Vector) is a random 128-bit value that ensures identical plaintexts produce different ciphertexts, preventing pattern analysis. A new IV should be generated for each encryption operation.
Common Use Cases
- File Encryption: Protecting sensitive files on disk (e.g., BitLocker, FileVault, VeraCrypt all use AES).
- HTTPS/TLS: AES is the most common cipher in TLS connections that secure web traffic.
- VPN Tunnels: IPsec and WireGuard VPNs use AES to encrypt network traffic.
- Database Encryption: Encrypting sensitive columns (credit cards, SSNs) at rest using AES.
- Messaging Apps: End-to-end encrypted messaging (Signal, WhatsApp) uses AES as part of their encryption protocol.
- API Security: Encrypting sensitive payloads in API requests and responses.
AES Modes of Operation
| Mode | Description | Best For |
|---|---|---|
| CBC | Cipher Block Chaining — each block is XORed with the previous ciphertext block | General-purpose encryption, file encryption |
| GCM | Galois/Counter Mode — provides both encryption and authentication | Network protocols (TLS, IPsec), authenticated encryption |
| CTR | Counter mode — turns the block cipher into a stream cipher | Streaming data, parallel processing |
| ECB | Electronic Codebook — each block encrypted independently (not recommended) | Avoid for most use cases — reveals patterns |
How to Use This Tool
- Paste your plaintext into the input field.
- Enter a secret key (or generate one).
- Select the AES mode (CBC, ECB, or GCM) and key size.
- Click Encrypt to get the ciphertext.
- To decrypt, paste the ciphertext and click Decrypt.
Why Use This Tool?
- Military-grade AES encryption runs entirely in your browser.
- Your data and keys never leave your device.
- Supports multiple AES modes and key sizes for any use case.
- Perfect for developers testing encryption flows or securing sensitive text.
Frequently Asked Questions
Is AES-256 secure?
Yes. AES-256 is considered unbreakable with current technology. A brute-force attack on a 256-bit key would require 2256 operations — more than the number of atoms in the observable universe. It is approved for top-secret classified information by the U.S. government.
What is the difference between AES-128 and AES-256?
The key length: AES-128 uses a 128-bit key (10 rounds) while AES-256 uses a 256-bit key (14 rounds). AES-256 provides a larger security margin but is slightly slower. Both are considered secure for current applications.
Should I use the same IV for multiple encryptions?
No. Reusing an IV with the same key compromises security, especially in CBC and GCM modes. Always generate a new random IV for each encryption operation and transmit it alongside the ciphertext (the IV is not secret).