SECP256K1 curve encryption not working

[Hugo.Dev]

Hi, 

We are using ncs 2.4.0, working with a custom project based in matter lock sample.

We were using SECP256R1 curves for encryption, without issues, but we need to move to SECP256K1, and we are getting MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE error when trying to sign a message. 

Going deeper I´ve found the function returning error is mbedtls_ecdsa_sign, but AFAIU the implementation is within nrfxlib/nrf_security/src/libmbedcrypto.a

Then I cannot check why it is returning this error

I have already enabled MBEDTLS_ECP_DP_SECP256K1_ENABLED in config file.

Any help will be appreciated.

Hugo

[dejans]

Hi,

Do you build your application as non-secure?

Do you use nrf_oberon crypto library?

Best regards,
Dejan

[Hugo.Dev]

Hi, thanks for the reply.

Yes, we do use oberon.

And we are building on top of the matter sample code, using mcuboot. I´m not 100% sure if that is secure or non-secure.

[Hugo.Dev]

Just for adding some more info.

I´ve taken lock matter sample, enabled k1 curve by adding 

config MBEDTLS_ECP_DP_SECP256K1_ENABLED
	default y

in kconfig file

Then I´ve added test code for signing a messge, it fails with -0x4E80 code

[dejans]

Hi,

Could you provide full error log?

Best regards,
Dejan

[Hugo.Dev]

There is no error log

mbedtls_ecdsa_write_signature calls mbedtls_ecdsa_write_signature_restartable which calls ecdsa_sign_det_restartable which calls mbedtls_ecdsa_sign which returns -0x4E80 error

And, as far as I understand the source code from mbedtls_ecdsa_sign is within modules/nrfxlib/nrfxlib/nrf_security/src/libmbedcrypto.a, so I cannot see why it returns error.

[dejans]

Hi,

SECP256K1 is not listed as supported in nrf_oberon crypto library.

Best regards,
Dejan