"It's a quick & dirty solution, but works. A shared nostr account is created for the secret chat / group. Its nsec can be shared via link, qr code or invite message from a single-use anonymous account," Martti Malmi explained.
"Users can then communicate using the shared account's messages-to-self. Iris signs the inner messages with your own key, but the arrangement could be used for anonymous group messaging as well," he added.
"Martti's submission with Iris did not qualify for the full bounty as only Iris users can initiate a group chat," was clarified in the announcement.
"The remaining 1 BTC is open to any popular nostr client that can create e2e encrypted nostr group chats with an interoperable standard via a merged NIP."
"We are excited by all of the interest from around the world in this bounty program and expect to make more announcements about claimed bounties soon," added the organization.