ATECC608A datasheet(41/81 Pages) MICROCHIP

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5.2.2

GenKey Command

The GenKey command is used to generate ECC private keys, ECC public keys from private keys or generate a

public key digest. This command is only applicable for those slots designated to be ECC private or public keys.

Running this command on a non-ECC slot will result in an error.

5.2.2.1

Private Key - Stored in TempKey

The GenKey command can be used to generate an ephemeral ECC private key and place it in SRAM where there is

no limit on writing to a memory location. This key cannot be read out but may be used by the ECDH command.

Table 5-42. Command Parameters

Opcode

(1 Byte)

Mode

(1 Byte)

KeyID

(2 Bytes)

OtherData

(3 Bytes)

Comment

0x40

0x04

0xFF FF

0x00 00 00

• Private key stored in TempKey

• Public key generated and output on the bus

Table 5-43. Output Response GenKey Stored in TempKey

Name

Size

Response

1 byte

If an ECC Fault code has been generated due to a command error

64 bytes

Public keys X and Y coordinate the command’s success

5.2.2.2

Public Key Generation

If the slot has been so configured, the ECC public key can be regenerated from a stored ECC private key and output

on the bus. In addition, if so desired, a public key digest can also be generated and stored in TempKey at the same

time.

For the ATECC608A-TNGLoRaWAN, the public key can be generated from the stored private key in Slot 1. Optional

digest generation is also allowed.

Table 5-44. Input Parameters - Public Key Generation

Opcode

(1 Byte)

Mode

(1 Byte)

KeyID

(2 Bytes)

OtherData

(0 Bytes)

Description

0x40

0x00

0x00 0[Slot]

—

Public key generated and output on the bus

0x40

0x08

0x00 0[Slot]

—

• Public key generated and output on the bus

• Public key digest generated and stored in TempKey

Table 5-45. Output Response - Public Key Generation

Name

Size

Response

1 byte

ECC Fault code if command fails

64 bytes

Public keys X and Y coordinate the command’s success

Public Key Digest Generation

A SHA256 Hash is performed over 128 bytes to generate a digest from the public key.

ATECC608A-TNGLoRaWAN

Device Commands

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