Which key settings does SM4 decrypt require?

Supply the SM4 key and the IV needed by the selected mode. Set the key representation before checking its byte length.

Why does SM4 output differ from another tool?

Match Mode, including any NoPadding suffix. Select Input and Output explicitly because hexadecimal text and raw input represent different bytes.

How should I copy SM4 decrypt input and output?

Select the actual Input representation before running the operation. Choose Hex output when you need to preserve arbitrary bytes during copying. A readable result or a Complete label alone does not verify the message or its sender.

SM4 Decryption | Tool Factory

Tool workspace

Your input stays in this browser.

Needs input

You can run the tool again after any change.

Input

Options

Key format

Key

IV format

Mode

Input

Output

Your result appears here

Apply SM4 Decrypt with explicit key, format, and algorithm settings. Enter the data and key material, choose the parameters, then review the result.

This tool runs open-source code from CyberChef by GCHQ (Apache License 2.0). See open-source credits.

SM4 Decryption uses SM4 block decryption to process the supplied input. It recovers plaintext from the matching ciphertext and settings. The mode list includes CBC/NoPadding and ECB/NoPadding, rather than a separate Padding control.

It recovers plaintext from the matching ciphertext and settings. The mode list includes CBC/NoPadding and ECB/NoPadding, rather than a separate Padding control. Processing runs in the browser for this catalog category, so the result depends on the supplied bytes and settings. Processing runs in the browser.

This tool performs the selected algorithm locally; it does not provide application trust or key management.

Instructions

Provide text or data for this tool.
Copy the complete output of the paired encrypt operation, not its displayed plaintext. This applies to SM4 Decryption.
Match key, IV, mode, and padding before expecting abc. This applies to SM4 Decryption.

Example

Input: First encrypt ASCII abc with SM4, CBC, key 000102030405060708090a0b0c0d0e0f, and an all-zero 16-byte IV. Paste that Hex ciphertext here.

Settings: SM4 Decryption: Key length: 16 bytes. Non-ECB IV length: 16 bytes. CBC and ECB apply padding unless their /NoPadding variants are selected. Input: Hex; Output: Raw for the paired text fixture.

Result: It recovers plaintext from the matching ciphertext and settings. The mode list includes CBC/NoPadding and ECB/NoPadding, rather than a separate Padding control. Processing runs in the browser for this catalog category, so the result depends on the supplied bytes and settings.

Limits

SM4 Decryption: 16-byte blocks determine alignment requirements when padding is disabled.
SM4 Decryption: Readable plaintext does not prove that ciphertext is authentic.