If You Don’t Want AES and ChaCha20 … There’s SM4

While AES has been proven to be secure, it hasn’t stopped Google from promoting ChaCha20. While AES is highly secure, in some applications…

If You Don’t Want AES and ChaCha20 … There’s SM4

While AES has been proven to be secure, it hasn’t stopped Google from promoting ChaCha20. While AES is highly secure, in some applications it is perhaps too resource-intensive for some devices. ChaCha20 — a stream cipher — often has lesser processing requirements. So while AES and ChaCha20 are popular, in China, OSCCA (Organization of State Commercial Administration of China) has also authorized SM4 for public use [here]:

Figure 1

The method was invented by Shu-Wang in 2003 and focused on efficient Wi-Fi use. It was then published as SM4 in 2012 by OSCCA. Overall, SM4 uses a 128-bit key, a 128-bit cipher block, has 32 rounds, and uses an 8-bit S-box. Each round uses XOR, 32-bit circular shifts and S-Box operations:

Figure 2

In this case rki is the round key, and provides 32 bits of the encryption key each round. The S-box function takes an 8-bit value and then maps to an output 8-bit value:

Figure 3

In each round with the T box (see Figure 2), we use four of the S-boxes for each of the four eight-bit values.

The latest version of OpenSSL now implements SM4 [here]:

And we can implement with [here]:

Linux command: echo -n "Hello" | openssl enc -sm4 -pass pass:"qwerty" -e -base64 -S 241fa86763b85341
Windows command: echo | set /p =  "Hello" | openssl enc -sm4 -pass pass:"qwerty" -e -base64 -S 241fa86763b85341
Message: Hello
Mode: sm4
Password: qwerty
Salt: 241fa86763b85341
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