AES Encryption/Decryption Tool
Professional AES symmetric encryption with 6 modes and 5 padding options
Encryption Configuration
What is AES Encryption?
AES (Advanced Encryption Standard) is the most widely used symmetric encryption algorithm globally, approved by the NSA for protecting TOP SECRET information. AES evolved from the Rijndael cipher designed by Belgian cryptographers Joan Daemen and Vincent Rijmen, and was officially published by NIST in 2001 as a replacement for the aging DES algorithm. AES uses block encryption with a fixed block size of 128 bits (16 bytes) and supports three key lengths: 128, 192, and 256 bits, corresponding to AES-128, AES-192, and AES-256 security levels. Longer keys provide higher security but slightly slower performance. As a symmetric encryption algorithm, AES uses the same key for both encryption and decryption, making it far more efficient than asymmetric encryption. AES has extensive applications: in network security, TLS/SSL protocols use AES to protect web browsing and email transmission; in storage security, tools like BitLocker and FileVault use AES to encrypt user data; in database security, many systems support AES column-level encryption; in IoT, AES is widely used for secure device-to-device communication. This tool supports all 6 AES encryption modes (ECB, CBC, CFB, OFB, CTR, GCM) and 5 padding schemes to meet various encryption needs.
How to Use
Basic Operations
- Select encryption mode (GCM recommended for encryption + integrity verification)
- Select padding scheme (GCM/CFB/OFB/CTR modes use no padding automatically)
- Select key length (256-bit for highest security, 128-bit for best performance)
- Enter key or click 'Generate Random Key' to create one automatically
- For modes requiring IV, enter or generate an initialization vector
- Enter plaintext (for encryption) or ciphertext (for decryption) in the left panel
- Results appear automatically in the right panel
- Click 'Copy' to copy results, or 'Swap' to exchange input and output
Encryption Modes
Padding Schemes
Usage Tips
- Keys should be generated using cryptographically secure random numbers, avoid guessable strings
- Use a different random IV for each encryption, never reuse IVs
- GCM mode recommends 12-byte (96-bit) IVs for optimal performance and security
- CTR and GCM modes support parallel processing for faster encryption of large data
- Keys and IVs can be entered in hexadecimal, text, or Base64 format
- Hex key lengths: 128-bit = 32 chars, 192-bit = 48 chars, 256-bit = 64 chars
Examples
Basic Encryption
Encrypt Chinese text using CBC mode
Plaintext: Hello, World!
Key: 0123456789abcdef0123456789abcdef
IV: fedcba9876543210fedcba9876543210
Mode: CBC / PKCS#7 / 128-bit
Ciphertext (hex): 7a8b9c0d1e2f...GCM Authenticated Encryption
Use recommended GCM mode for encryption + integrity protection
Plaintext: Sensitive data
Key: Randomly generated 256-bit key
IV: Randomly generated 12 bytes
Mode: GCM / No padding / 256-bit
Ciphertext: IV automatically prependedFile Content Encryption
Encrypt configuration files or sensitive data
Paste file content into input
Select AES-256-CBC mode
Generate and save key + IV
Encrypted output can be safely stored or transmittedFAQ
Q: Which encryption mode should I choose?
A: GCM mode is recommended. It provides both encryption and data integrity verification through GHASH authentication tags, preventing ciphertext tampering. GCM is the default cipher in TLS 1.3 and is widely considered the most secure AES mode. If integrity verification is not needed, CBC is a classic choice. CTR is suitable for high-performance parallel encryption scenarios. Avoid ECB as it's insecure and leaks data patterns.
Q: Why is ECB mode insecure?
A: ECB mode produces identical ciphertext blocks for identical plaintext blocks, meaning encrypted data retains the original data's patterns. The most famous example is an image encrypted with ECB mode - while pixel values are encrypted, the overall image outline remains clearly visible. Additionally, ECB mode is vulnerable to replay attacks and block substitution attacks. In practice, always use more secure modes like CBC or GCM.
Q: How do I choose key length?
A: AES-256 provides the highest security, approved by the NSA for TOP SECRET information protection, suitable for high-security scenarios. AES-192 offers medium security for confidential information. AES-128 is sufficiently secure for general applications with slightly faster performance. In the quantum computing era, AES-256 is considered resistant to Grover's algorithm and is recommended as the preferred choice.
Q: What is IV and why is it needed?
A: IV (Initialization Vector) is an additional input parameter that ensures the same plaintext produces completely different ciphertexts in different encryption processes. Without IV, identical plaintexts would always produce identical ciphertexts, allowing attackers to infer plaintext information by observing ciphertext patterns. Except for ECB, all other modes require IV. CBC, CFB, and OFB modes need 16-byte IVs, while GCM recommends 12-byte (96-bit) IVs. IVs don't need to be kept secret, but each encryption must use a different random IV.
Q: How to safely store and transmit keys?
A: Keys are the core of encryption systems and must be strictly protected. For storage: use professional Key Management Systems (KMS) or Hardware Security Modules (HSM), avoid hardcoding keys in code or storing them in plaintext configuration files. For transmission: always use secure channels (like TLS/SSL), never transmit keys through email, chat tools, or other insecure channels. Key rotation is also an important security practice - regularly changing keys reduces the risk of key compromise.
Q: Why is encrypted data longer than the original?
A: Ciphertext is longer than plaintext mainly for three reasons: 1) Padding: block encryption modes require data to be padded to multiples of 16 bytes, even one byte short adds a full block; 2) IV: modes like CBC and GCM typically prepend the IV to the ciphertext, adding 12-16 bytes; 3) Encoding: output formats (hexadecimal or Base64) increase data size - hex encoding doubles the size, Base64 adds about 33%.
Q: Is this tool's encryption secure?
A: This tool uses the aes-js library to execute standard AES algorithms in the browser, and the algorithm implementation is secure. However, note that: 1) Browser environments are less secure than dedicated encryption devices; 2) Keys may be exposed through browser extensions or console; 3) This tool is suitable for learning, testing, and general use - production environments should use professional encryption services. All data processing happens locally in your browser and is not uploaded to any server.
Q: How does GCM mode differ from other modes?
A: GCM (Galois/Counter Mode) is an authenticated encryption mode, differing from others in: 1) GCM provides both encryption and data integrity verification (authentication), while others only provide encryption; 2) GCM uses 12-byte IVs, others typically use 16 bytes; 3) GCM appends an authentication tag to ciphertext during encryption and verifies it during decryption to ensure data hasn't been tampered with; 4) GCM supports parallel processing with better performance than CBC. This tool's GCM implementation automatically prepends the IV to ciphertext and extracts it during decryption.
Q: When is padding needed?
A: Block encryption modes (ECB, CBC) require data length to be multiples of 16 bytes, hence padding is needed. Stream modes (CFB, OFB, CTR, GCM) convert block ciphers to stream ciphers and don't need padding. When selecting stream modes, this tool automatically sets no padding. Padding choice: PKCS#7 is the most common and unambiguous; ISO 7816-4 and ANSI X.923 are mainly for specific industry standards; zero padding is simple but may cause ambiguity.
Q: How to verify encryption results are correct?
A: The best way to verify encryption results is to decrypt using the same key and IV to see if you can recover the original plaintext. Steps: 1) Record the key, IV, mode, and padding used during encryption; 2) Paste ciphertext into input, switch to decrypt mode; 3) Use the exact same key, IV, mode, and padding; 4) If decryption result matches the original plaintext, encryption is correct. GCM mode provides additional integrity verification - if ciphertext is tampered with, decryption will fail.