How to convert private key from text to hex value

[Srinivas V]

HI Team,

We have generated the private key from "nrfutil" tool and we want to integrate to our code, how to extract from python generated file "private.key" file to hex value.

Eg:

         -----BEGIN EC PRIVATE KEY-----
MHcCAQEEIJX5obLZDyFEMZtW3BrfvreBI90xu9QmcfdkbKxfvMPhoAoGCCqGSM49
AwEHoUQDQgAEPKntlb897rDjpAp72pkz+Om4MPn7HvUFz9cBNGZzaLGyfM/VO6qf
6ZjW5BrSfsixYNc5D2qaTgJj7zg5ACDONQ==
-----END EC PRIVATE KEY-----

Regards,

Srinivas.V

[Turbo J]

Nrfutil knows a --help argument, which can be used for specific usages, too: "nrfutil.exe keys display --help"

>nrfutil.exe keys display --key pk compromized_key.pem --format hex
Public (verification) key pk:
b16873663401d7cf05f51efbf930b8e9f83399da7b0aa4e3b0ee3dbf95eda93c35ce20003938ef63024e9a6a0f39d760b1c87ed21ae4d698e99faa3bd5cf7cb2

>nrfutil.exe keys display --key pk compromized_key.pem --format code

/* This file was automatically generated by nrfutil on 2020-06-20 (YY-MM-DD) at 16:42:01 */

#include "stdint.h"
#include "compiler_abstraction.h"

/** @brief Public key used to verify DFU images */
__ALIGN(4) const uint8_t pk[64] =
{
    0xb1, 0x68, 0x73, 0x66, 0x34, 0x01, 0xd7, 0xcf, 0x05, 0xf5, 0x1e, 0xfb, 0xf9, 0x30, 0xb8, 0xe9, 0xf8, 0x33, 0x99, 0xda, 0x7b, 0x0a, 0xa4, 0xe3, 0xb0, 0xee, 0x3d, 0xbf, 0x95, 0xed, 0xa9, 0x3c,
    0x35, 0xce, 0x20, 0x00, 0x39, 0x38, 0xef, 0x63, 0x02, 0x4e, 0x9a, 0x6a, 0x0f, 0x39, 0xd7, 0x60, 0xb1, 0xc8, 0x7e, 0xd2, 0x1a, 0xe4, 0xd6, 0x98, 0xe9, 0x9f, 0xaa, 0x3b, 0xd5, 0xcf, 0x7c, 0xb2
};

Unfortunately, the private key posted here is now compromized and you must generate a new one. Remember: This forum is public.

[Srinivas V]

Hi Turbo,

Thanks for your reply, what ever you are showing is public key , but we want to see the private key in hex format the way public key shown here instead of text , why means we are testing ecc functionalities with hard coded keys (private/public) in our test app, for that we need this key pair. Originally we are not disclosing the private key.

Regards,

Srinivas.V

[Turbo J]

Left as excercise for the readers - see the --help command above. Hint: You need to change ONE character in each example...