ATECC508A datasheet(70/109 Pages) MICROCHIP

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Excluding the digest generation operation described above, the slot indicated by this command must be

configured by means of KeyConfig.Private to contain an ECC private key, and SlotConfig.IsSecret must

be set to one, or else this command will fail. If the KeyConfig.KeyType does not indicate an ECC curve

supported by this device, then this command will also return an error. Prior to the Configuration zone

being locked, this command will always return an error.

Once the Data zone has been locked, the following additional restrictions are enforced:

•

Private Key Creation:

–

Bit 13 of the corresponding SlotConfig must be set to one.

–

If KeyConfig.ReqAuth is set to one, then a prior authorization using KeyConfig.AuthKey must

have been performed.

•

Public Key Generation:

–

KeyConfig.PubInfo must be set to one.

–

If KeyConfig.ReqAuth is set to one, then a prior authorization using KeyConfig.AuthKey must

have been performed.

The following applies to all private key creation operations regardless of whether or not the Data zone

has been locked:

•

This command writes only those bytes necessary to create a private key of the type specified. The

remaining bytes within the slot are unaffected by this command.

•

When creating and writing a random key into the Data zone, the GenKey command always returns

the public key regardless of the value of the PubInfo bit within the KeyConfig area.

•

If the corresponding SlotLocked bit is zero, then this command returns an error.

•

There is a small statistical probability that the generated key will be unacceptable, in which case

this command will return a single byte containing the ECC fault code (see Table 9-3). In this

circumstance the command should be re-run and will usually generate a key correctly in the

subsequent iteration.

Table 9-20. Input Parameters

Name

Size

Notes

Opcode

GenKey

0x40

Param1

Mode

See Table 9-22.

Param2

KeyID

Specifies the slot where a private ECC key is generated, the private key slot used to

generate a public key or a public key location used as part of a digest generation.

Data

OtherData

If KeyID points to a public key, then these bytes replace Param1 and Param2 in the

message calculation.

Table 9-21. Output Parameter

Name

Size

Notes

Response 1 or 64 Public Key X and Y coordinates. ECC fault code if generated private key was unacceptable.

ATECC508A

Security Commands

Datasheet Complete

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