CC2640: SHA256

Nicolas Venturo

Part Number: CC2640
Other Parts Discussed in Thread: AES-128, , BLE-STACK

Hello,

I need to calculate the hash of a block of data using SHA256. I noticed there's a ROM implementation (which I've been using with rom_crypto.h and rom_crypto.c), which I've been using for AES-128, which also contains SHA256 functions. These functions, however, return an uint8_t (a status code, according to the comments), that isn't documented in the places I've looked. Are there any result codes I should check against?

Thanks

over 9 years ago

0 Nathan Siegel over 9 years ago

TI__Genius 10980 points

Hi,

It is just success and failure (zero and nonzero) for these functions.

-Nathan

0 Nicolas Venturo over 9 years ago in reply to Nathan Siegel

Intellectual 810 points

Thanks Nathan.

By the way, while doing some research I came upon this thread (https://e2e.ti.com/support/wireless_connectivity/bluetooth_low_energy/f/538/t/433086), where a TI employee (svendt) says that the ROM implementation is not safe to use. Is svendt referring to these same ROM functions that rom_crypto.c calls?

0 Nathan Siegel over 9 years ago in reply to Nicolas Venturo

TI__Genius 10980 points

Hi,

That is referring to a link to an older version of CC26xxware, assuming you are using the most recent cc26xxware_2_24_02_17393 that comes with tirtos_cc13xx_cc26xx_2_20_01_08.

-Nathan

0 Nicolas Venturo over 9 years ago in reply to Nathan Siegel

Intellectual 810 points

I don't know about cc26xxware versions, I'm using ble_cc26xx_01_01_44627 and tirtos_simplelink_2_13_00_06 (I manually added the ROM crypto files because they weren't present in that release), because these were the latest versions available (I think) when I started development back in June 2016.

0 Nathan Siegel over 9 years ago in reply to Nicolas Venturo

TI__Genius 10980 points

Hi,

Where did you get the files from that you manually added? If they were from the wiki that was mentioned in svendt's post, then yes, that is what he was referring to.

-Nathan

0 Nicolas Venturo over 9 years ago in reply to Nathan Siegel

Intellectual 810 points

I don't remember where I downloaded from, and I cannot seem to find the link right now. This document seems to describe the same one that I have, though:

Does this mean that I cannot safely use the SHA256 ROM funtions then? Are there any alternatives?

0 JXS over 9 years ago in reply to Nicolas Venturo

TI__Guru** 105180 points

Hi Nicolas,

The SHA256 ROM functions are safe to use since you supply the workzone RAM. Since there really isn't any way the APIs can fail, you can ignore the status.

Please note that the SHA256 and AES ROM APIs are not available in CC2640R2F. You can use the AES co-processor and supply a flash based SHA lib for these crypto operations.

Best wishes

0 Nicolas Venturo over 9 years ago in reply to JXS

Intellectual 810 points

Thank you JXS.

Are the AES-128 ECB functions also safe? They work in-place, but no workzone is provided.

My only motivation to switch to the CC2640R2F is the extra Flash available to my program due to more functionality being embedded in the ROM. Do you have an estimate on the code size needed to use the AES co-processor and calculate a SHA256? Those are the only crypto features that I need, and I want to make sure I'll actually have more memory than I do at the moment.

0 JXS over 9 years ago in reply to Nicolas Venturo

TI__Guru** 105180 points

No problem, Nicolas.

You can use the AES ROM crypto function as well. The BLE-Stack in your version uses the AES co-processor so there is no conflict.

Typical sizes for SHA256 lib is ~ 1.5 kB.

Best wishes

0 Nicolas Venturo over 9 years ago in reply to JXS

Intellectual 810 points

Great! Thank you so much. I'll see if I can convince the rest of the team to switch to the R2F then!

0 Siva Krishna Kattinti over 9 years ago in reply to JXS

Expert 1090 points

hi can you please provide the sha256 lib link. so that i can include that sha256 in my project.

thanks,

siva.

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CC2640: SHA256