CAAM : AES-ECB application ?

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CAAM : AES-ECB application ?

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jumeyer
Contributor II

Hi all,

I'm new to IMX6.

I would like to develop a little application in c language which use the CAAM cryptographic hardware accelerator (CHA).

I've 2 main problem:

- I think I don't understand very well all concepts: job descriptor/trusted descriptor , job rings, shared descriptors, etc...

- I try to read some register (like MCFGR — Master Configuration Register for example) and it spawn an error.

I've read the Document Number: IMX6DQ6SDLSRM :

Security Reference Manual for i.MX6Dual, 6Quad, 6Solo, and 6DualLite Families of Applications Processors

but for beginning I would like a little application example. It's easier in order to understand the main idea.

As concerning the register reading,

I use this (simple) command in my c program :

#define reg32_read(addr)     *((volatile uint_32_t *) (addr))

and in my program, when I call :

reg32_read(0x02100004); //0x02100004 : Master Configuration Register address

the program return me :

[1] + stopped (signal)  ./caam_test

I don't understand the real problem.

Is it a right problem ?

Is their a register setting that I missed in order to read all registers?

How to read/write into register in order to use CHA of CAAM ?

Is there some code examples of AES ECB mode encryption using the CAAM ?

Please, could you help me please ? Any suggestions are welcome...

Thx

10 Replies

401 Views
Yuri
NXP TechSupport
NXP TechSupport

  Please look at my comments below.


1.

  You may look at the Platform SDK - it contains an example regarding blob using.

"The i.MX6 Platform SDK is located at:

Below is SDK link :

https://www.freescale.com/webapp/Download?colCode=i.MX6_PLATFORM_SDK&location=null

Summary page :

http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=i.MX6Q&fpsp=1&tab=Design_Tools_Tab

2.

  There is “sm_test.c” (Linux) example (located at "drivers/crypto/caam/sm_test.c")

for testing encapsulating and decapsulating of black keys.

3.

  Also, please look at the enclosed example : simple job that will decrypt
a 1024-byte message using AES in CBC mode. I hope it helps.

[00] B080000F     jobhdr: stidx=0 len=15

[01] 12200010     ld: ccb1-ctx len=16 offs=0

[02] 00000002     ptr->@0x225a84662

[03] 25A84662

[04] 02000010     key: class1-keyreg len=16

[05] 00000001     ptr->@0x1e767e1b5

[06] E767E1B5

[07] 8210010C     operation: cls1-op aes cbc init-final dec

[08] 22120400     fifold: class1 msgdata-last1 len=1024

[09] 00000002     ptr->@0x23ab4850a

[10] 3AB4850A

[11] 60700000     fifostr: msgdata ext

[12] 00000004     ptr->@0x4de37d42c

[13] DE37D42C

[14] 00000400     extlen=1024

  The steps involved are:

[01] Load the CBC IV into the Class 1 Context Register

[04] Load the 128-bit AES key into the Class 1 Key Register

[07] Configure the AESA CHA to decrypt with the CBC mode

[08] Read 1024 bytes of input data with the FIFO LOAD command. The data will be

directed to the Class 1 Alignment Block, and the 'last data' flag will be presented

along with the end of it.

[11] Store the deciphered data with the FIFO STORE command. The 'ext' flag means

that the length field in the first word is not used. Instead, the length comes after the

pointer. The class field value is not interpreted when data source/type is 'msgdata',

which means the OFIFO.

   This is a good model for data encryption and decryption. If not all of the data is passed

through at once, but processing will continue in other job(s), it might be necessary to

store the context register as the last step of the descriptor. How many bytes to store is

dependent upon the algorithm and mode. This requirement will also affect the 'algorithm

state' value, as init-final is proper for a complete message. RC4 (the AFHA) has a

separate solution in this regard, as the 'context' is 258 bytes (256 bytes of key material of

the RC4 SBox and 1-byte each of the context pointers i and j).

  Below are some details how  to create a Black Key :

Load the desired key into a key register, (Class 1,Class2, PKHA E, or AFHA Sbox),

using the Key command with the NoWriteBack bit cleared, and then write out the

key register using the FIFO Store command.

  The FIFO Store command OutputDataType field is used to specify the source of

the key, the encryption algorithm (AES-ECB or AES-CCM) and the KEK (either JDKEK

or TDKEK). Note that only a Trusted Descriptor may specify using the TDKEK for creating

a Black Key. Otherwise, an error will result.

  A Black Key will be larger than a plaintext key. When using AES-CCM mode, the Black Key

will be 12 bytes longer than the plaintext key. Six of the extra bytes contain the nonce for

the Black Key, and the other six bytes contain a 48-bit integrity check tag. If the tag is

incorrect when a descriptor loads an AES-CCM Black Key, the descriptor will stop with an error.

When loading a Black Key into a key register using the Key command, the value

specified in the length field is the length of the plaintext key, not the size of the Black

Key buffer. When creating a Black Key using the FIFO Store command, the value in the

length field is the length of the plaintext key. The buffer must be large enough to hold the

encrypted key plus the additional padding.


Have a great day,
Yuri

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401 Views
ma_sreelakshmi
Contributor II

Hi Yuri,

1.Can you provide descriptors for AES-CMAC ?

2.From the above code i changed the operation command, but i am not getting output... Can you help me with the changes i have to do to get CMAC?

3.Can i use same fifostore for CMAC as well or are we using store command(to take MAC from context register)?

I read the SRM for iMX6. Is there anything else i need to consider?

Kindly reply asap.

Best regards

Sreelakshmy M A

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Yuri
NXP TechSupport
NXP TechSupport

Hello,

  I've not found AES-CMAC example.

Regards,

Yuri.

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ma_sreelakshmi
Contributor II

Hi Yuri,

0xB080000A,
0x12200010,                         /*Load IV*/
(uint32_t)init_vector,
0x02000010,                          /*Key*/
(uint32_t)key,
0x8210060C,                       /* CMAC*/
0x22120010,                        /*fifo load plain text*/
(uint32_t)plaintext,
0x52200010,                       /*store cipher text*/
(uint32_t)out_ptrr

I have tried with this descriptors for AES-CMAC....

i am getting this as answer(which is not the correct one)... There is no error detecting for CAAM...something is processing and i got this...


0x6b
0x4f
0x25
0x13
0x4b
0xa9
0xef
0xd0
0x52
0x46
0xfd
0x87
0x36
0xaa
0x9e
0x1f

What is wrong in my code?

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Yuri
NXP TechSupport
NXP TechSupport

ma.sreelakshmi@gmail.com 

Hello,

  I think it makes sense to create new thread regarding AES-CMAC

Regards,

Yuri.

401 Views
ma_sreelakshmi
Contributor II

Hello Yuri,

I got correct output with this descriptor... The test vector i used were wrong in the above scenario...

PS:Those who are beginners in CAAM try to use NIST test vectors...Don't depend upon any online AES, SHA calculators..

Thank you for the reply

Best regards

Sreelakshmy M A

401 Views
ma_sreelakshmi
Contributor II

Hi Yuri,

To give the address of plane text, key etc.., why you are using another descriptors 00000002,00000001,00000004 etc...?

Can we give the plane text and array like below?(AES-CBC encryption)

 0x12200010, 
(uint32_t)init_vector,       ??

Can you tell me the mistake in my descriptor?

0xB080000A,
0x12200010,                            /*Load IV*/
(uint32_t)init_vector,
0x02000010,                            /*Key*/
(uint32_t)key,
0x8210010D,
0x22120010,                            /*plain text*/
(uint32_t)plaintext,
0x60300010,                             /*store cipher text*/
(uint32_t)out_ptr

For me what happening is ...I am getting an encrypted value and when i decrypt that cipher text i am getting plain text as well... but that cipher text is not same as in the test vectors... 

Thanks in advance

Sreelakshmy M A

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ma_sreelakshmi
Contributor II

Hi Yuri,

I got output with the above descriptors.. It was some other problem in data arrays..

Best regards

Sreelakshmy M A

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jumeyer
Contributor II

Hi Yuri,

First : Great thank you for your detailed explanation and links (that are not broken...)

But some little problems...

1- I don't find "drivers/crypto/caam/sm_test.c"file.. (neither in "/sdk/drivers" nor "/output/')

2- the detailed explanation of the code execution (in 3) is very interesting.

     but where this code is located/loaded ? in which memory address ?

     Is possible to write directly in memory/registers thanks to the code like this for example :

#define part1 B080000F;

#define part2 22 12200010;

#define part3 12 00000002;

#define part4 2225A84662;

#define part5 02000010;

#define part6 00000001;

#define part7 E767E1B5;

#define part8 8210010C;

#define part9 22120400;

#define part10 00000002;

#define part11 3AB4850A;

#define part12 60700000;

#define part13 00000004;

#define part14 DE37D42C;

#define part15 00000400;

uint32_t job_descriptor[] =

{

     part1,

     part2,

     part3,

     part4,

     part5,

     part6,

     part7,

     part8,

     part9,

     part10,

     part11,

     part12,

     part13,

     part14,

     part15

};

Specify in job rings registers the address of this job descriptor ?

and run the job, read the result ?

In other words, can I do the work myself, without using the SDK ? writing directly the value of registers ?

But which registers must I set up to do this simple work... ?

3- when I've built the SDK. All built file are in "/output" directory.

there are no directory for my boards : (SabreLite or RioTboard...)

And when I load and test every sdk_unit_test_caam.elf or sdk_unit_test_caam.bin it return an error...

CAAM register configuration is not the same for all mx6dq processor ?

I'm still stuck...

I hope read you soon,

Julien.

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Yuri
NXP TechSupport
NXP TechSupport

Julien, good day !

  I should clarify that, the items in my previous reply relate to fully
different approaches. The first (Platform SDK) is stand alone example.
The second relates to Linux

http://www.freescale.com/webapp/Download?colCode=L3.0.35_4.1.0_ER_SOURCE_BSP&appType=license&locatio...

Summary Page :

i.MX 6 Series Software and Development Tool R|Freescale

And the third is just a "text" example, that may be used as base for own design.

~Yuri.