AES ROM function: AES_CCM_DecryptData

user1730962

Other Parts Discussed in Thread: CC1310

I find there is a ROM function for AES CCM decryption in SDK: AES_CCM_DecryptData.

But, my application get faults in this function call. Because, this function, AES_CCM_DecryptData, wants to jump to an invalid address.

The screenshot for my debug enviroment is attached.

Is there any inilizations required for this function call? Do I miss something for this function call?

Please let me know about that.

Thanks,

over 9 years ago

0 Richard W. over 9 years ago

TI__Genius 14860 points

Hi,

the function you mention is part of the internal driverlib implementation. We ship the CC1310 with a bunch of driverlib and TI-RTOS kernel functions already preprogrammed in ROM.

TI-RTOS provides a high-level crypto driver. But if you want to use the AES hardware accelerator based on driverlib in a Ti-RTOS application, then you can use the following code snippet for inspiration:

#include <driverlib/crypto.h>
#include <ti/drivers/power/PowerCC26XX.h>

void testAes()
{
    /* Enable the AES module */
    Power_setDependency(PowerCC26XX_PERIPH_CRYPTO);
    /* Prohibit standby. */
    // This is only necessary when doing blocking calls in the following code
    // or when leaving this function while using the crypto module
    Power_setConstraint(PowerCC26XX_SB_DISALLOW);

    /* Set up the variables */
    uint8_t aesKey[16] = {
            0x5a, 0x69, 0x67, 0x42, 0x65, 0x65, 0x41, 0x6c,
            0x6c, 0x69, 0x61, 0x6e, 0x63, 0x65, 0x30, 0x39
    };
    uint8_t inputData[]= {
            0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
            0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F
    };
    uint8_t encryptedData[sizeof(inputData)] = { 0 };
    uint8_t outputData[sizeof(inputData)] = { 0 };

    enum {
        Encrypt = 0x01,
        Decrypt = 0x00,
        InterruptsEnabled = 0x01,
        InterruptsDisabled = 0x00,
    };

    // The crypto HW can store up to 8 keys.
    //
    // For 128 bit key all 8 Key Area locations from 0 to 8 are valid
    // However for 192 bit and 256 bit keys, only even Key Areas 0, 2, 4, 6
    // are valid.
    //
    uint8_t keyIndex = CRYPTO_KEY_AREA_0;

    /* Load the key to the crypto unit */
    CRYPTOAesLoadKey((uint32_t*)aesKey, keyIndex);

    /* Start the encryption in blocking mode */
    CRYPTOAesEcb((uint32_t*)inputData, (uint32_t*)encryptedData, keyIndex, Encrypt, InterruptsDisabled);
    while (CRYPTOAesEcbStatus() != AES_SUCCESS);

    /* Decrypt the data again in blocking mode */
    CRYPTOAesEcb((uint32_t*)encryptedData, (uint32_t*)outputData, keyIndex, Decrypt, InterruptsDisabled);
    while (CRYPTOAesEcbStatus() != AES_SUCCESS);

    volatile int i;
    for (i = 0; i < sizeof(inputData); i++)
    {
        if (inputData[i] != outputData[i])
        {
            while (1);
            /* Fail */
        }
    }

    /* Allow standby and release the crypto module. */
    Power_releaseConstraint(PowerCC26XX_SB_DISALLOW);
    Power_releaseDependency(PowerCC26XX_PERIPH_CRYPTO);
}

All AES-related functions are stored in ROM if you use driverlib in ROM.

0 user1730962 over 9 years ago in reply to Richard W.

Intellectual 905 points

Hi Richard

These functions you mentioned, CRYPTOAesLoadKey/CRYPTOAesEcb, are NOT in ROM. No ROM address define for these function, and these functions are linked in flash.

0 Lukas Hegetschweiler over 8 years ago in reply to Richard W.

Prodigy 50 points

Thanks for the example!!

There is only a litte mistake: after two times calling CRYPTOAesEcb it will not return successfully.

To avoid this you have to call:

CRYPTOAesEcbFinish();

0 Sven Depoorter over 8 years ago in reply to Richard W.

Intellectual 290 points

Hello Richard,

The crypto driver didn't work for me, I kept getting a AES_KEYSTORE_READ_ERROR, but your example works and seems more straight forward.

What would be the advantages from your code compared to using the crypto driver?

Thanks and best regards,

Sven

0 Richard W. over 8 years ago in reply to Sven Depoorter

TI__Genius 14860 points

There is no real advantage and if only the high-level Crypto driver would have a better API and better documentation, I would always prefer to use the high-level driver instead of the low-level DriverLib API.

0 Sven Depoorter over 8 years ago in reply to Richard W.

Intellectual 290 points

Thanks Richard! The high level implementation is very confusing. Your example works with the addition of CRYPTOAesEcbFinish();.

Br,

Sven

Sub-1 GHz

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AES ROM function: AES_CCM_DecryptData