One site's step in the threshold key-generation chain

The site derives its own secret share from its predecessor's cumulative public key, keeps the share, and returns only the new cumulative public key. The share is generated at the site and is never a return value, so no other party can hold it.

Usage

keygen_round(site, ...)

Arguments

site

a LocalSite, or a user-defined subclass of RemoteSite.

...

method-specific arguments; the built-in method takes cc, the crypto context, and prev_pk, the cumulative public key from the previous site in the chain (NULL for the lead site, which starts the chain with a fresh keypair).

Value

the cumulative public key including this site's contribution. Never a secret key.

Details

Called by make_threshold_master(), once per site, in order. A RemoteSite implementation must do the same thing at the far end: receive a public key, generate and retain a share locally, send a public key back. Nothing secret crosses the wire in either direction.

See also

make_threshold_master(), partial_decrypt().