ATSHA204 datasheet(7/65 Pages) ATMEL

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Atmel ATSHA204 [DATASHEET]

8740D

−CRYPTO−3/12

2.1.1.1 SlotConfig (Bytes 20 – 51)

The 16 SlotConfig elements are used to configure the access protections for each of the 16 slots within the ATSHA204. Each

configuration element consists of 16 bits, which control the usage and access for that particular slot/key. The SlotConfig field is

interpreted according to the following table when the data zone is locked. When the data zone is unlocked, these restrictions

do not apply — all slots may be freely written and none may be read.

Table 2-2.

SlotConfig Bits (per slot)

Bit #

Name

Description

 3

ReadKey

Use this keyID to encrypt data being read from this slot using the Read command. If zero,

then this slot can be the source for the CheckMac copy operation (see Section 3.3.6). See

the description for bit 6 in this table, the Read command description in Section 8.12, and

Table 2-3 for more details.

Note:

Do not use zero as a default. Do not set this field to zero unless the CheckMac

copy operation is explicitly desired, regardless of any other read/write restrictions.

CheckOnly

1 = The key stored in the slot can be used only for CheckMac command. It can also be

used for GenDig if the subsequent use of TempKey is CheckMac. The key cannot be

used by any other command, either directly as KeyID in the input parameter list or via

TempKey.

0 = The key stored in the slot can be used by all crypto commands.

SingleUse

1 = The key stored in the slot is “single use.” See Section 3.3 for more details.

Ignored for keys in slots 8-14.

0 = There are no usage limitations.

EncryptRead

1 = Reads from this slot will be encrypted using the procedure specified in the Read

command description (Section 8.12) using ReadKey (bits 0 – 3 in this table) to

generate the encryption key. No input MAC is required. If this bit is set, then IsSecret

must also be set (see also Table 2-3).

0 = Clear text reads may be permitted.

IsSecret

1 = The contents of this slot are secret: Clear text reads are prohibited, and both 4-byte

reads and writes are prohibited. This bit must be set if EncryptRead is one or if

WriteConfig has any value other than <Always> to ensure proper operation of the

device.

0 = The contents of this slot should not contain confidential data or keys.

See Table 2-3 for additional information.

 11

WriteKey

Use this key to validate and encrypt data written to this slot.

See Section 8.14 for additional information.

 15

WriteConfig

Controls the ability to modify the data in this slot.

See Table 2-4 and Section 8.14 for additional information.

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