AN3992

Firmware description

Doc ID 022369 Rev 3

9/22

3.2

AES encryption mode

In this mode, the AES accelerator performs the encryption of a 128-bit plain text using the

provided 128-bit key to compute the cipher text. In the example below, the plain text

“CR95HF and STM8L” is encrypted using the “Ultralow Power” key.

The cipher text, computed by the AES hardware accelerator, is:

●

in ASCII format:

♫σCΣm2DM5kìL″ß▀⌠

●

in hex format: 0E E5 43 E4 6D 32 44 4D 35 6B 8D 05 4C 22 DF F4

(according to “code page 437").

See http://en.wikipedia.org/wiki/Code_page_437

Figure 3.

AES hardware accelerator: encryption mode

MS19975V1

CR95HF and STM8L

AES hardware accelerator

Encryption mode

128-bit cipher text

128-bit plain text

♫σCΣm2DM5kìL"ß▀⌠

Encryption Key:

"ultra-low power.”