NRF52811-QCAA-R datasheet(88/444 Pages) NORDIC

88 / 444 page

Peripherals

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

generating a key-stream.

RFU

EPL

MIC

CRC

READY

TXEN

END

key-stream

generation

KSGEN

encryption

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

CRYPT

ENDKSGEN

SHORTCUT

PPI

Figure 30: On-the-fly encryption of short packets (MODE.LENGTH = Default) using a PPI connection

6.4.6 Decrypting packets on-the-fly in radio receive mode

When the AES CCM is decrypting a packet on-the-fly at the same time as the RADIO is receiving it, the AES

CCM must read the encrypted packet from the same memory location as the RADIO is writing to.

The INPTR on page 95 pointer in the AES CCM must therefore point to the same memory location as

the PACKETPTR pointer in the RADIO, see Configuration of on-the-fly decryption on page 88.

AES CCM

RFU

EPL

L+4 RFU

Unencrypted packet

Encrypted packet

MIC

Scratch area

CCM data

structure

MODE = DECRYPTION

RADIO

RXEN

From remote

transmitter

H: Header (S0)

L: Length

RFU: reserved for future use (S1)

PL: unencrypted payload

EPL: encrypted payload

OUTPTR

INPTR

PACKETPTR

SCRATCHPTR

CNFPTR

Figure 31: Configuration of on-the-fly decryption

In order to match the RADIO’s timing, the KSGEN task must be triggered early enough to allow the key-

stream generation to complete before the decryption of the packet shall start.

For short packets (MODE.LENGTH = Default) the KSGEN task must be triggered no later than when the

START task in the RADIO is triggered. In addition, the CRYPT task must be triggered no earlier than when

the ADDRESS event is generated by the RADIO.

If the CRYPT task is triggered exactly at the same time as the ADDRESS event is generated by the RADIO,

the AES CCM will guarantee that the decryption is completed no later than when the END event in the

RADIO is generated.

This use-case is illustrated in On-the-fly decryption of short packets (MODE.LENGTH = Default) using a

PPI connection on page 89 using a PPI connection between the ADDRESS event in the RADIO and the

CRYPT task in the AES CCM. The KSGEN task is triggered from the READY event in the RADIO through a PPI

connection.

4454_140 v1.0

NRF52811-QCAA-R bảng dữ liệu(PDF) 88 Page - Nordic Semiconductor

NRF52811-QCAA-R bảng dữ liệu(HTML) 88 Page - Nordic Semiconductor

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

bảng dữ liệu tải về

Link URL