#!/bin/bash
K=000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004
echo "$K" | wc -c
# generate secp384r1 key with provided K value
# 30 3E                      SEQUENCE, len 62
#   02 01 01                 version = 1
#   04 30 <bytes of K value>         privateKey OCTET STRING
#   A0 07 06 05 2B 81 04 00 22   [0] parameters = secp384r
printf '303e0201010430%s%s' "$K" 'a00706052b81040022' | xxd -r -p > key.der \
    && openssl ec -inform DER -in key.der -out private-key.pem \
    && openssl ec -in private-key.pem -noout -text 

# https://emudhra.we-have-a-problem.com/
# https://gist.github.com/Fluepke/9a103c7f990c3cc2fb5002f7476f2f48