Question on counter initial value for AES CTR on STM32WB

1 reply
915 views

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

This topic has been closed for replies.

Nicolas ANQUET

ST Employee

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

Sign up

Click below to sign in

Login to the community

Click below to sign in