ATECC608A datasheet(31/81 Pages) MICROCHIP

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Note: 1 - [bb_bb] Indicates the 4-bit value that represents the slot being locked.

Table 5-11. Slot Lock Output

Name

Size

Description

Response 1 byte 0x00 if the command successfully locks the slot. An error code will output if the command fails.

5.1.4

Nonce Command

The Nonce command generates a nonce (number used once) for use by a subsequent command by combining a

random number (which can be generated internally or externally) with an input value from the system. The resulting

nonce is stored internally in three possible buffers: TempKey, Message Digest Buffer, and Alternate Key Buffer.

Instead of generating a nonce, a value may be passed to the device if so desired.

5.1.4.1

Nonce - Random

When the Nonce command is run in Random mode, it generates a new nonce based on the input values shown in

the tables below. If Param2 is 0x00 00, then a new random number is generated based on the internal RNG. If

Param2 is 0x80 00, a value stored in TempKey is used to generate a new nonce instead and the random number

generator is not run. TempKey must be valid prior to running the Nonce command in this case. Upon completion, the

TempKey.SourceFlag is set to Rand.

It is recommended that the 20 bytes of data sent to the device be generated from a random source to prevent replay

attacks.

Table 5-12. Random Nonce Input Parameters

Opcode

Mode

Param2

Data

Description

0x16

0x00 or 0x01

0x00 00

20 bytes

• 32 bytes written to TempKey

• Output is from the RNG

• SHA256 digest includes the random number

0x00 or 0x01

0x80 00

20 bytes

• 32 bytes written to TempKey

• Output is the SHA256 Hash value

• SHA256 digest includes the TempKey

Table 5-13. Random Nonce Output Response

Name

Input Param2

Size

Description

Response

0x00 00

32 bytes

Random number

0x80 00

32 bytes

New TempKey value

Notes:

TempKey.SourceFlag set to ‘0’ on successful completion of the command indicating the nonce value was

random source.

TempKey.Valid set to ‘1’ on success.

Table 5-14. Nonce SHA256 HASH Calculation

# of Bytes

Input Data Param2 = 0x00 00

Input Data Param2 = 0x80 00

RandOut from random number generator

TempKey value from previous command

NumIn from input stream

Opcode (always 0x16)

Mode (0x00 or 0x01)

ATECC608A-TNGLoRaWAN

Device Commands

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