I am having an issue with handling large integers. I am trying to implement threshold secret sharing scheme by following the article in the link. I have modified the driver code to the following so that our secret key is practically large number instead of some pass phrase.
t, n = 3, 5
secret = 5238440126074724526414965738603764307730944402353374454036086258591065307597
print(f'Original Secret: {secret}')
shares = generate_shares(n, t, secret)
print(f'Shares: {", ".join(str(share) for share in shares)}')
pool = random.sample(shares, t)
print(f'Combining shares: {", ".join(str(share) for share in pool)}')
print(f'Reconstructed secret: {reconstruct_secret(pool) }')
I am getting the following error at due to line return int(round(Decimal(sums), 0)) from reconstruct_secret function :
decimal.InvalidOperation: [<class 'decimal.InvalidOperation'>]
But it works just fine when I shorten my secret to 5238440126074724526414965. I have no idea how I can modify the reconstruct_secret function to work according to my requirement. Any suggestions would be a great help.
Thanks to @Barmar, my problem was solved by increasing the precision of decimal module as follows:
from decimal import *
getcontext().prec = 100
Now I am able to reconstruct secret keys as per my requirement.