SM4 Encryption and Decryption

📖 Description

1. Why Choose SM4 for Domestic Projects?

When advancing "Xinchuang" transformation and ensuring the security of core systems, SM4 holds an irreplaceable position:

• National Standard Compliance: It is a necessary condition for critical infrastructure in government affairs, finance, energy, etc., to pass "Dengbao" (Multi-Level Protection) assessments and "Miping" (Cryptographic Application Security Evaluation).
• Balanced Structure: It employs a 128-bit block length and a 128-bit key length. Its iteration rounds (32 rounds) and unique nonlinear transformation (S-box) design make it highly robust against differential and linear cryptanalysis.
• Superior Performance: The algorithm logic is concise, making it suitable for both high-volume data encryption on high-end servers and efficient operation on resource-constrained devices like smart cards and embedded systems.

2. Core Feature Analysis

This site's tool integrates all encryption modes of SM4, ensuring 100% compatibility with backend systems:

A. Supports Multiple Encryption Modes

• ECB (Electronic Codebook): Simple and direct, suitable for encrypting very short data (e.g., key distribution).
• CBC (Cipher Block Chaining): The most recommended mode. By introducing an IV (Initialization Vector), it ensures that the same plaintext produces different ciphertexts each time, defending against pattern analysis attacks.
• CTR (Counter Mode): Converts block encryption into stream encryption, suitable for high-performance streaming data processing.

B. Automatic Padding Handling

• Supports padding schemes like PKCS7Padding (default standard), automatically handling plaintext that is not a multiple of 16 bytes, ensuring error-free encryption and decryption.

C. Encoding and Formatting

• Input Mode: Supports UTF-8 text or Hex data.
• Output Format: Provides two ciphertext display formats: Base64 (convenient for transmission) and Hex (convenient for development and debugging).

D. Privacy Protection: Browser-Side Local Computation

• Local Processing: All SM4 computations are performed locally in your browser.
• Zero Upload Risk: Your original data and the 16-byte "key" are never uploaded to the server. Even for highly confidential projects, you can confidently perform rapid joint debugging within the webpage.

3. Brief Operation Guide

Encryption (Hide Data):

1. Input Plaintext: Enter text or Hex in the plaintext area.
2. Set Key: Enter a 16-byte (128-bit) key (e.g., 1234567812345678).
3. Select Mode: Choose CBC or ECB (CBC with a random IV is recommended).
4. Click Encrypt: Obtain the ciphertext and click "Copy" to save it.

Decryption (Recover Data):

1. Paste Ciphertext: Paste the ciphertext in Base64 or Hex format.
2. Input Key: Enter the same 16-byte key used for encryption.
3. Click Decrypt: Instantly recover the original plaintext information.

4. Common Parameter Reference Table

5. Why Choose This Site's SM4 Assistant?

• Cross-Platform Interoperability: Strictly adheres to the National Cryptography Administration standards. Calculation results are completely consistent with mainstream cryptographic libraries like GmSSL and BouncyCastle.
• Extremely Lightweight: Loads in seconds, no need to install cumbersome desktop software.
• Completely Free: No registration required, unlimited usage, tailored to programmers' habits for frequent joint debugging.

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