from Crypto.PublicKey import ECC
from Crypto.Protocol.KDF import PBKDF2
from Crypto.Hash import SHA512
from Crypto.Random import get_random_bytes
from secrets import randbelow

FILE = 'exchange.bin'

prime = 0xffffffffffffffffffffffffffffffff000000000000000000000001

def generate_secret(c = 0):
	# 'DER' format for byte output
        return ECC.generate(curve='NIST P-224').export_key(format='DER')

def H(secret):
	# secret should be bytearray[], pref. from generate_secret() function
	salt = get_random_bytes(16)
	key = PBKDF2(generate_secret(), salt, 64, count=1000000, hmac_hash_module=SHA512)
	return key[32:] # first 32 bytes of generated key

def coin_toss():
	x = randbelow(2 ** 64)
	if x & 1:
		return False
	else:
		return True