ATECC608A datasheet(45/81 Pages) MICROCHIP

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Procedure to Verify a Message with a Stored Key

If so required, validate the public key before using the Verify command.

If so required, authorize the public key before use.

Write the 32-byte digest of the message to either the TempKey or Message Digest Buffer using the Nonce

command in Fixed mode.

Write the System Nonce to either the lower or upper 32 bytes of the Message Digest Buffer.

4.1.

If TempKey contains the message digest, then store the System Nonce in the lower 32 bytes of the

Message Digest Buffer.

4.2.

If the message digest is stored in the lower 32 bytes of the Message Digest Buffer, then store the

System Nonce in the upper 32 bytes of the Message Digest Buffer. The user needs to write both the

message digest and the System Nonce at one time using the Nonce command.

Issue the Verify command. Include the Mode, KeyID, which specifies the public key slot, the 64-byte

signature and the slot # of the internal public key.

The output will return:

6.1.

One byte success, fail or error code if MAC is not required.

6.2.

A 32-byte MAC, if specified by the mode or an error code, if the command fails.

Table 5-53. Command Parameters

Opcode

(1 Byte)

Mode

(1 Byte)

Public Key

(2 Bytes)

Data Field (64 Bytes)

Comment

Signature

(64 Bytes)

0x45

0x00

0x00, 0[Slot]

R value

S value

- Message stored in TempKey

0x20

0x00, 0[Slot]

R value

S value

- Message stored in Message Digest Buffer

0x80

0x00, 0[Slot]

R value

S value

- Message stored in TempKey

Validation MAC is returned

0xA0

0x00, 0[Slot]

R value

S value

- Message stored in Message Digest Buffer

Validation MAC is returned

Table 5-54. Output Response - Verify Stored

Name

Mode

Size

Response

0x00 or 0x20

1 byte

• 0x00 - If signature is verified

• 0x01 - If signature does not match

• Error code - If there is a failure due to some other reason

0x80 or 0xA0

32 bytes

1 byte

• Validation MAC - If signature is verified

• 0x01 - If signature does not match

• Error code - If there is a failure due to some other reason

Table 5-55. Validation MAC - Verify Stored

The validation MAC input locations vary based on where the message is stored.

Size

(Bytes)

Message in TempKey

Message in Message Digest Bufffer

Contents of the IO protection key

Message from TempKey

First 32 bytes message from the Digest Buffer

ATECC608A-TNGLoRaWAN

Device Commands

Complete Datasheet

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