Failed to use curve25519 in M52810

RE: Failed to use curve25519 in M52810

Vishwas Jain — Tue, 01 Sep 2020 09:56:17 GMT

Hello,

I am using nRF52840, SDK16 & SoftDevice140.

I am integrating pm_init()(Peer Manager) into my project and I am getting error 0xFFFFB180 from mbedtls_ecp_gen_keypair().

Kindly help me out!

RE: Failed to use curve25519 in M52810

hejianxuan — Sat, 05 Jan 2019 18:03:46 GMT

Dear Thorsrud,

Thanks for your great support!

I have not traced the error into mbed TLS.

I need mbed TLS because of AES CCM. I would encrypt/decrypt data by AES CCM after got secret key by ECDH.

It seems that 52810 cannot meet my demand. I should try 52832.

Thank you!

Jianxuan

RE: Failed to use curve25519 in M52810

Einar Thorsrud — Fri, 04 Jan 2019 09:02:20 GMT

Hi Jianxuan,

Ah, I did not spot that. The mbed TLS code is somewhat obfuscated. It seems likely that there is a memory allocation failure. Have you verified it by tracing the error further into mbed TLS?

We have not tested ECDH properly on the nRF52810 (only the combinations which there are examples for in the SDK are part of the release testing). Fitting this into a nRF52810 with the S112 SoftDevice will be quite tight, though it depend on the amount of RAM needed for S112 (depending on configuration).

You will probably have better luck by using the Oberon backend instead of mbed TLS as is less far memory hungry. Here (devzone.nordicsemi.com/.../nrf_5F00_crypto_5F00_ecdh_5F00_examples_5F00_more_5F00_boards.zip) are untested project files of the ECDH example for more boards with and without a SoftDevice configured to use the Oberon backend. This includes a pca10040e project with SoftDevice. Note that the example is not updated to enable and use the SoftDevice, and that the application start address is probably too low for practical BLE applications (except for beacons), but you have some headroom when using the Oberon backend.

RE: Failed to use curve25519 in M52810

hejianxuan — Thu, 03 Jan 2019 15:52:46 GMT

Dear Thorsrud,

We know that ECDH need a lot of RAM and flash. I am worried that limitation of M52810 resource should cause uncertain problem while ECDH. You know, there is no pca10040e support in ECDH example.

Thus, I want to know whether Nordic ran ECDH on M52810? If true, could you share ECDH project for pca10040e?

Especially, ECDH project with softdevice for pca10040e would be highly appreciated! I could copy your project directly. That is great!

Thanks,

Jianxuan

RE: Failed to use curve25519 in M52810

hejianxuan — Thu, 03 Jan 2019 15:34:33 GMT

In nRF5_SDK_15.2.0\external\mbedtls\include\mbedtls\bignum.h:

#define MBEDTLS_MPI_CHK(f) do { if( ( ret = f ) != 0 ) goto cleanup; } while( 0 )

This macro assign f to ret. In other words, the variable "ret" has been set before it is read.

RE: Failed to use curve25519 in M52810

Einar Thorsrud — Thu, 03 Jan 2019 14:45:02 GMT

There seems to be a bug in mbed TLS. You can see in <SDK15.2>\external\mbedtls\library\ecp_curves.c, on line 660 there is a variable "ret" which is defined, but it is never set before it is read. I suspect the proper fix is to delete line 660 and line 680-684, and always return 0 from ecp_use_curve25519().

RE: Failed to use curve25519 in M52810

hejianxuan — Thu, 03 Jan 2019 14:27:31 GMT

The error is returned on line 124. The return value is 0xfffffff0.

RE: Failed to use curve25519 in M52810

Einar Thorsrud — Thu, 03 Jan 2019 13:57:09 GMT

I see. Then the NRF_ERROR_CRYPTO_INTERNAL return value should come from either line 124 or line 141 in <SDK 15.2>\components\libraries\crypto\backend\mbedtls\mbedtls_backend_ecc.c. Can you check using a debugger which it is?

If the error is returned on line 124, then can you see the return value from mbedtls_ecp_group_load() on line 75? And if it comes from the call to mbedtls_ecp_gen_keypair(), what is the return value from it?

RE: Failed to use curve25519 in M52810

hejianxuan — Thu, 03 Jan 2019 13:41:37 GMT

mbed TLS backend.

RE: Failed to use curve25519 in M52810

Einar Thorsrud — Thu, 03 Jan 2019 13:23:31 GMT

Hi Jianxuan,

The error code is NRF_ERROR_CRYPTO_INTERNAL. Which crypto backend have you enabled for Curve25519 in your projects sdk_config.h?

RE: Failed to use curve25519 in M52810

hejianxuan — Thu, 03 Jan 2019 13:17:18 GMT

Dear Thorsrud,

SDK version is 15.2.0. The error code is 0x00008516.

By the way, crypto init snippet is listed below:

err_code = nrf_mem_init();
APP_ERROR_CHECK(err_code);

err_code = nrf_crypto_init();
APP_ERROR_CHECK(err_code);

Thanks,

Jianxuan

RE: Failed to use curve25519 in M52810

Einar Thorsrud — Thu, 03 Jan 2019 08:50:24 GMT

Hi,

Which SDK version are you using? What is the error code returned from the call to nrf_crypto_ecc_key_pair_generate()?