NRF52811-QCAA-R7 datasheet(85/444 Pages) NORDIC

85 / 444 page

Peripherals

Bit number

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

Reset 0x00000001

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1

Access

Field

Value ID

Value

Description

RW DISABLEINDEBUG

Disable the protection mechanism for NVM regions while in

debug mode. This register will only disable the protection

mechanism if the device is in debug mode.

Disabled

Disabled in debug

Enabled

Enabled in debug

6.4 CCM — AES CCM mode encryption

Cipher block chaining - message authentication code (CCM) mode is an authenticated encryption

algorithm designed to provide both authentication and confidentiality during data transfer. CCM combines

counter mode encryption and CBC-MAC authentication. The CCM terminology "Message authentication

code (MAC)" is called the "Message integrity check (MIC)" in Bluetooth terminology and also in this

document.

The CCM block generates an encrypted keystream that is applied to input data using the XOR operation

and generates the 4 byte MIC field in one operation. The CCM and radio can be configured to work

synchronously. The CCM will encrypt in time for transmission and decrypt after receiving bytes into

memory from the radio. All operations can complete within the packet RX or TX time. CCM on this device

is implemented according to Bluetooth requirements and the algorithm as defined in IETF RFC3610,

and depends on the AES-128 block cipher. A description of the CCM algorithm can also be found in NIST

Special Publication 800-38C. The Bluetooth specification describes the configuration of counter mode

blocks and encryption blocks to implement compliant encryption for BLE.

The CCM block uses EasyDMA to load key, counter mode blocks (including the nonce required), and to

read/write plain text and cipher text.

The AES CCM supports three operations: key-stream generation, packet encryption, and packet

decryption. All these operations are done in compliance with the Bluetooth specification.13

key-stream

generation

KSGEN

encryption / decryption

CRYPT

ENDKSGEN

ENDCRYPT

SHORTCUT

Figure 26: Key-stream generation followed by encryption or decryption. The shortcut is optional.

6.4.1 Key-steam generation

A new key-stream needs to be generated before a new packet encryption or packet decryption operation

can be started.

A key-stream is generated by triggering the KSGEN task and an ENDKSGEN event will be generated when

the key-stream has been generated.

Key-stream generation, packet encryption, and packet decryption operations utilize the configuration

specified in the data structure pointed to by CNFPTR on page 95. It is necessary to configure this

pointer and its underlying data structure, and the MODE on page 94 register before the KSGEN task is

triggered.

13 Bluetooth AES CCM 128 bit block encryption, see Bluetooth Core specification Version 4.0.

4454_140 v1.0

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