# Multi-party decryption, no central decrypter

Recently a bank had a costly mistake that resulted in their master private key being exposed.

Through this thread, I learned about multi-party key storage with Adi Shamir's secret sharing scheme as the basis, very cool.

In the naive setup, there's still a person/machine that must do the final decryption which knows the full key.

What scheme(s) allows no central decrypter?

A guess I have is two or more 'groups/keys' separately encrypt/decrypt the message so no one group can ever have the keys to the kingdom.

Or is there a way for the final decrypter to decrypt w/o actually knowing the master key such that only one Adi Shamir scheme is necessary?

Thanks!

• My understanding of Section 6.3.1 says each party member (Pi) takes their portion of the private key (Xi) and performs a decryption that does produces an output (Di) where i is just who they are. The beauty of the ElGamal scheme is (Di) is a proper partial decryption that can be passed onto the next party member and they can perform their own partial decryption. Once enough members (t+1) doing partial decryptions, you'll get plain text M. Amazing. – nitsujri Jun 22 at 3:20