SM4 Calculator

Encrypt and decrypt data using the SM4 (Chinese National Standard) symmetric block cipher algorithm.

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About This Tool

This SM4 online calculator provides a complete implementation of the SM4 encryption algorithm (also known as SMS4). SM4 is a 128-bit block cipher standardized by the Chinese government for commercial applications. The tool supports both encryption and decryption operations with ECB and CBC modes, along with PKCS7 padding. Simply enter your 128-bit key (32 hex characters), plaintext or ciphertext, select the operation mode, and get instant results. All calculations happen locally in your browser for maximum security.

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How to Use

Enter a 128-bit key in hexadecimal format (32 characters like '0123456789ABCDEFFEDCBA9876543210').
Enter the plaintext (for encryption) or ciphertext (for decryption) in hexadecimal format.
Select the operation: Encryption or Decryption.
Choose the mode: ECB (Electronic Codebook) or CBC (Cipher Block Chaining).
If using CBC mode, enter an initialization vector (IV) in hexadecimal format.
Click the 'Calculate' button to perform the SM4 operation.
View the results in the output section below.

Frequently Asked Questions

Find Quick Answers

What is SM4?

SM4 is a 128-bit block cipher encryption algorithm standardized by the Chinese State Cryptography Administration. It's used for commercial encryption in China and is similar to AES in security level.

What key format should I use?

The key must be exactly 128 bits, represented as 32 hexadecimal characters (0-9, A-F). For example: '0123456789ABCDEFFEDCBA9876543210'.

Does this tool support file encryption?

No, this is a text-based calculator for hexadecimal input/output. For file encryption, you would need specialized software that implements SM4.

Is my data secure?

Yes, all calculations are performed locally in your browser. No data is sent to any server, ensuring complete privacy.

What padding does the tool use?

The tool uses PKCS7 padding for data that isn't a multiple of 128 bits. This is automatically applied during encryption and removed during decryption.

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