Doc ID024209 Rev 2

27/30

AN4240

How to generate the M1-M5 parameters

– CID = counter value (28 bit)

•

M5 = CMAC,K4(M4)

(128 bit size)

– A CMAC is performed over using key K4 over M4

Note:

If a key has it is Write Protect (WP) attribute set, the key cannot ever be updated or erased.

See Table 3. Key Attributes. Write Protection should only be used when the user is

absolutely certain that the key is never changed or erased. Setting Write Protection on any

single key means that the part cannot be reset to its factory state using the DEBUG

CHALLENGE/AUTHORIZATION sequence.

In order to generate M1-M5 parameters some precompiled executable files have been

used.

The following sources were downloaded from www.hoozi.com and modified. Original author

is Niyaz PK.

AES_ENC_CBC_CMD.c

AES_ENC_ECB_CMD.c

AES_MP_KDF_CMD.c

The following sources was based on an original program by Junhyuk Son and Jicheol Lee:

AES_CMAC_CMD.c

A.2

Cryptographic keys used

For the demo code, a set of pre-calculated keys and values are used which are shown in

Table 5. These values found in some of the header files provided with the examples. To use

user-defined keys, the user needs to use offline scripts to calculate the necessary values.

Table 5. Examples of Keys used for the project

Slot name

Key ID

[hex]

Address offset

[hex]

Key flags

[bin]

128-bit key word 0 word 1word 2 word 3

BOOT_MAC

_

KEY

0x2

0x060

00011

12340000 00000000 00000000 00005678

KEY_1

0x4

0x0A0

00001

2FF8B03C 5C540546 5A9C94BD 2D863279

KEY_2

0x5

0x0C0

00001

85852FF8 E7860C89 B3AB9D63 B8D6288F

KEY_3

0x6

0x0E0

01001

A36FF144 FB6D5E2C DA0D2894 DA0D2894

KEY_4

0x7

0x100

00101

86078C1A BCDCC6B6 C52C851D

E5652BF5

KEY_5

0x8

0x120

00011

043A1A50 DB3954D2 22FEB37F 1F678FCA

KEY_6

0x9

0x140

00001

4B957750 4B957750 6F75C3E0 5C8DCD59

KEY_7

0xA

0x160

00011

2B7E1516 28AED2A6 ABF71588 09CF4F3C

KEY_8

0xB

0x180

00111

10AF4B5B 024195B9 1730D7F5 94C87E19

KEY_9

0xC

0x1A0

00001

93346F4C 6A8ABCCD 37D52249 291F4138

KEY_10

0xD

0x1C0

01011

68B674CB 8198A250 3A285100 F4DDC40A