ATSHA204A datasheet(13/93 Pages) MICROCHIP

13 / 93 page

Bit

Name

Description

IsSecret

0 =

The slot is not secret and allows clear read, clear write, no MAC check and no

Derivekey Command.

1 = The slot is secret. Reads and writes if allowed, must be encrypted.

EncryptRead

0 =

Clear reads are permitted.

1 =

Requires the slot to be Secret and encrypted read to access.

LimitedUse(1)

0 = No limit on the number of time the key can be used.

1 =

Limit on the number of time the key can be used based on the UseFlag (or

LastKeyUse) for the slot.

CheckOnly

0 = This slot can be used for all crypto commands.

1 =

This slot can only be used for CheckMac and GenDig followed by CheckMac

Commands.

3-0

ReadKey

Slot of the key to be used for encrypted reads.

If 0x0, then this slot can be used as the source slot for the CheckMac/Copy Command.

Note:

LimitedUse bit was previously named SingleUse.

Table 2-6. Write Configuration Bits — Derivekey Command

Bit 15 Bit 14 Bit 13 Bit 12 Source Key(1) Description

Target

DeriveKey command can be run without authorizing MAC (Roll).

Target

Authorizing MAC required for DeriveKey command (Roll).

Parent

DeriveKey command can be run without authorizing MAC

(Create).

Parent

Authorizing MAC required for DeriveKey command (Create).

—

Slots with this value in the WriteConfig field may not be used as the

target of the DeriveKey command.

Note:

The source key for the computation performed by the DeriveKey command can either be the key

directly specified in Param2 (the “Target”) or the key at SlotConfig<Param2>. WriteKey (the

“Parent”).

See Section Key Values for more details.

ATSHA204A

Device Organization

DS40002025A-page 13

ATSHA204A датащи(PDF) 13 Page - Microchip Technology

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