NRF51822-CFAB-R datasheet(34/130 Pages) NORDIC

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nRF51822 Product Specification v3.3

4.5

AES CCM Mode Encryption (CCM)

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.

Note: The CCM terminology "Message Authentication Code (MAC)" is called the "Message Integrity

Check (MIC)" in Bluetooth terminology and this document and the nRF51 Series Reference

Manual are consistent with Bluetooth terminology.

The CCM block generates an encrypted keystream, applies it to the 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, as described in the nRF51 Series Reference Manual. 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 the NIST Special Publication 800-38C. The Bluetooth Core Specification v4.0 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.

4.6

Accelerated Address Resolver (AAR)

Accelerated Address Resolver is a cryptographic support function to implement the "Resolvable Private

Address Resolution Procedure" described in the Bluetooth Core Specification v4.1. "Resolvable Private

Address Generation" should be achieved using ECB and is not supported by AAR. The procedure allows two

devices that share a secret key to generate and resolve a hash based on their device address.

The AAR block enables real-time address resolution on incoming packets when configured according to the

description in the nRF51 Series Reference Manual. This allows real-time packet filtering (whitelisting) using a

list of known shared secrets (Identity Resolving Keys (IRK) in Bluetooth).

The following table outlines the properties of the AAR.

Table 14 AAR properties

4.7

Random Number Generator (RNG)

The Random Number Generator (RNG) generates true non-deterministic random numbers derived from

thermal noise that are suitable for cryptographic purposes. The RNG does not require a seed value.

4.8

Watchdog Timer (WDT)

A countdown watchdog timer using the low-frequency clock source (LFCLK) offers configurable and robust

protection against application lock-up. The watchdog can be paused during long CPU sleep periods for low

power applications and when the debugger has halted the CPU.

Instance

Number of IRKs supported for simultaneous resolution

AAR

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