This video (from 2011) describes the Decentralized Attribute-based Encryption that we can use for targeting messages (such as BTC bounties as #[0] mentioned) to badge holder criteria.

It DOES require a public setup parameter that is created in a trustless manner.

To safely implement this, we would need to decide to use block data from a specific future Bitcoin block and then we could implement the model AFTER that block has passed, using it for the public setup parameter.

Badge issuers would then be able to issue a key (can be public) to badge holders as part of the issuance process. All badge issuers need to use the same global setup parameter when generating it.

She describes it well: https://www.microsoft.com/en-us/research/video/decentralizing-attribute-based-encryption/