CC2642R: AESGCM - IV only 12 bytes support

Daan Schilder1

Part Number: CC2642R

Hi,

SDK: simplelink_cc13x2_26x2_sdk_4_20_01_04
SDK: simplelink_cc13x2_26x2_sdk_4_30_00_54

Following statements have been made in the AESGCM driver module:

/* The only supported ivLength is 12 for now */

is there already a driver which supports ivLenght of 12? I really need this for one of my projects

Kind regards,

Daan

over 5 years ago

0 Clément over 5 years ago

TI__Guru** 101540 points

Hi,

I confirm the AESGCM driver currently available in the SDK (4.20 and 4.30) only supports ivLenght of 12.

Maybe you can explain the need you have and we can find a different approach for you.

Best regards,

0 Daan Schilder1 over 5 years ago in reply to Clément

Intellectual 530 points

Hi Clement,
A colleague just found out how wolfSSL is doing this, after which we together implemented a sollution.

Edit the AESGCMCC26XX.c source file (recommended to copy into your workspace instead of editting the SDK) with the following lines (search for the first 3 lines of this snippet).

    HWREG(CRYPTO_BASE + CRYPTO_O_AESIV0) = ((uint32_t *)operation->iv)[0];
    HWREG(CRYPTO_BASE + CRYPTO_O_AESIV1) = ((uint32_t *)operation->iv)[1];
    HWREG(CRYPTO_BASE + CRYPTO_O_AESIV2) = ((uint32_t *)operation->iv)[2];
    // HWREG(CRYPTO_BASE + CRYPTO_O_AESIV3) = 0x01000000;


    if(operation->ivLength > 12)
      HWREG(CRYPTO_BASE + CRYPTO_O_AESIV3) = ((uint32_t *)operation->iv)[3];
    else
      HWREG(CRYPTO_BASE + CRYPTO_O_AESIV3) = 0x01000000;



Next off, create a GHASH function and hash the 16-byte IV with it (take wolfssl as your reference), also, please create a proper code formatting box for this forum

use the output as the IV argument of the GCM cipher.

0 Clément over 5 years ago in reply to Daan Schilder1

TI__Guru** 101540 points

Hi,

Thank you for sharing!

Kind regards,

Bluetooth®︎

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CC2642R: AESGCM - IV only 12 bytes support