Typical/max AES CCM time

[Jonathan]

In nRF51 PS, I read typical/max time for AES ECB are respectively 8.5 and 17µs. What would be those values for the whole AES-CCM operation (ie including MIC computation), on nRF51 and nRF52?

I'm planning to use AES CCM with timeslot API, if I can have a guaranteed timing, then I may simply require a slot long enough to perform the encryption, otherwise, I'll have to implement slot extension and possibly aborting the operation to try again later.

[bjorn-spockeli]

Hi Jonathan,

we not have any public numbers for the time it takes to encrypt/decrypt + MIC calculation for n number of bytes. However, according to the AES-CCM peripheral description

All operations can complete within the packet RX or TX time.

This means that the worst case encrypt/decrypt + MIC calculation will be

Packet Size( overhead( address, header, preamble, CRC) + payload) / 1 Mbps

You can use this to calculate the length of the timeslot.

Best regards

Bjørn