Threshold Cryptography
Threshold cryptography splits a key into n shares distributed among n parties, with at least t shares required to cooperate in performing a cryptographic operation — a single leaked share does not compromise security.
Purpose
It eliminates single points of failure by never concentrating the key in one party, protecting high-value keys such as CA private keys and root keys.
Mechanism
Key K is split into (K_1, ..., K_n) such that any t shares reconstruct K while t-1 shares reveal nothing. Signing/decryption is computed partially on the shares and combined, without ever reconstructing the key.
Use cases
- Threshold signatures for CA private keys
- Root DNSSEC KSK protection
- Cryptocurrency multisig wallets