NRF52811-QCAA-R datasheet(89/444 Pages) NORDIC

89 / 444 page

Peripherals

For long packets (MODE.LENGTH = Extended) the key-stream generation will need to be started even

earlier, for example at the time when the RXEN task in the RADIO is triggered.

Important: Refer to Timing specification on page 97 for information about the time needed for

generating a key-stream.

RFU

EPL

MIC

CRC

ADDRESS

RXEN

END

key-stream

generation

KSGEN

decryption

CRYPT

PPI

ENDKSGEN

ENDCRYPT

READY

START

SHORTCUT

RADIO

AES CCM

RU: Ramp-up of RADIO

P: Preamble

A: Address

H: Header (S0)

L: Length

RFU: reserved for future use (S1)

EPL: encrypted payload

: RADIO receiving noise

READY

PPI

Figure 32: On-the-fly decryption of short packets (MODE.LENGTH = Default) using a PPI connection

6.4.7 CCM data structure

The CCM data structure is located in Data RAM at the memory location specified by the CNFPTR pointer

Property

Address offset

Description

KEY

16 byte AES key

PKTCTR

Octet0 (LSO) of packet counter

Octet1 of packet counter

Octet2 of packet counter

Octet3 of packet counter

Bit 6 – Bit 0: Octet4 (7 most significant bits of packet counter, with Bit 6 being the most

significant bit) Bit7: Ignored

Ignored

Bit 0: Direction bit Bit 7 – Bit 1: Zero padded

8 byte initialization vector (IV) Octet0 (LSO) of IV, Octet1 of IV, … , Octet7 (MSO) of IV

Table 25: CCM data structure overview

The NONCE vector (as specified by the Bluetooth Core Specification) will be generated by hardware based

on the information specified in the CCM data structure from CCM data structure overview on page 89 .

Property

Address offset

Description

HEADER

Packet Header

LENGTH

Number of bytes in unencrypted payload

RFU

Reserved Future Use

PAYLOAD

Unencrypted payload

Table 26: Data structure for unencrypted packet

4454_140 v1.0

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