📖 Description

1. What is AES Encryption?

AES (Advanced Encryption Standard), also known as the Rijndael cipher, is a block cipher standard adopted by the U.S. federal government. It has become the most widely used symmetric encryption algorithm globally, employed to protect the transmission security of banking systems, government data, and various types of sensitive information.

Symmetric Encryption Property: AES is a symmetric encryption algorithm, meaning that encryption and decryption use the same "key".
High Security: AES supports key lengths of 128, 192, and 256 bits. For example, with a 256-bit key, the number of possible brute-force combinations is as high as $2^{256}$, making it virtually unbreakable with current computing power.

2. Core Parameter Configuration Guide

When using the AES tool, ensuring that the parameters are identical between the encrypting and decrypting parties is key to success.

Parameter Name	Options/Description	Recommendation
Cipher Mode (Mode)	CBC, ECB, CFB, OFB, CTR	Prefer CBC. ECB mode offers lower security and is not recommended for long texts.
Key	16/24/32 characters	Corresponds to 128/192/256-bit encryption.
Initialization Vector (IV)	16 characters	Required only in modes like CBC, CFB, OFB, etc., to increase encryption randomness.
Padding	PKCS7, ZeroPadding, NoPadding	Prefer PKCS7 (compatible with PKCS5), the most common standard currently.
Output Format	Base64, Hex	Since ciphertext is a binary stream, it is usually converted to a Base64 string for transmission.

3. In-depth Comparison of Common Cipher Modes

[Image comparing AES ECB and CBC modes with initialization vectors]

CBC (Cipher Block Chaining) Mode

This is the most commonly used mode. Each plaintext block is XORed with the previous ciphertext block before encryption. This mode requires an Initialization Vector (IV).

Advantages: High security; identical plaintext blocks produce different ciphertext blocks.
Disadvantages: The encryption process is serial, making it slightly slower than ECB.

ECB (Electronic Codebook) Mode

The simplest mode. Plaintext is divided into fixed-size blocks, and each block is encrypted independently.

Advantages: Fast speed, supports parallel computation.
Disadvantages: Identical plaintext blocks produce identical ciphertext blocks, making it vulnerable to pattern analysis attacks. Recommended only for encrypting very short, random data.

4. Frequently Asked Questions (FAQ)

Q: Why did decrypting data encrypted on this site with another tool fail?

A: Please check the following three points: 1. Are the modes consistent (e.g., both CBC)? 2. Are the padding methods consistent (e.g., both PKCS7)? 3. Are the encoding formats for the key and IV unified (UTF-8 vs Hex)?

Q: Which is better, AES-128 or AES-256?

A: AES-256 offers higher security but with slightly greater performance overhead. For the vast majority of civilian and commercial scenarios, AES-128 is sufficiently secure.

Q: What is the purpose of the Initialization Vector (IV)?

A: The IV ensures that even if the same plaintext is encrypted with the same key, the generated ciphertext is different each time. This effectively defends against replay attacks. In CBC mode, the IV must be 16 bytes (128 bits).

5. Why Choose This Site's AES Tool?

Fully Local Processing: Most online encryption/decryption sites send data to a backend server. This site uses pure frontend encryption technology; your key and plaintext never leave your browser, eliminating the risk of data leakage at its source.
Full Mode Support: Perfectly adapts to the encryption/decryption needs of various development environments (Java, C#, Python, Go, PHP).
Optimal Experience: Supports one-click copy, real-time conversion between Base64 and Hex, automatic reminders for 16-bit/32-bit key filling, reducing error rates.

For detailed AES knowledge, please refer to: AES In-depth Analysis: Structure, Mathematical Principles, and Security Comprehensive Analysis

AES Encryption and Decryption