FAQs
cancel
Turn on suggestions
Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.
Showing results for 
Search instead for 
Did you mean: 

Question on counter initial value for AES CTR on STM32WB

PADAM.1
Associate III

‎2020-12-26 12:10 PM

Hello

In chapter 22.4.9 of RM0434 Rev6 is stated:

Counter: a 32-bit big-endian integer that is incremented each time a block

processing is completed. The initial value of the counter must be set to 1.

Why can be the initial value of the counter not be set to 0 (as far as I know it is possible in standard)? Is this a bug?

Best regards

Paul

Labels:
0 Kudos
1 REPLY 1
Nicolas ANQUET
ST Employee

‎2021-01-25 12:01 AM

Hello Paul,

When initializing the AES for the first block what you are proposing makes sense. However, by doing as recommended in the RM0434, application can start AES-CTR computation at any block number (see principle of suspend-resume sequence).

Best regards,

Nicolas

0 Kudos
Top