I want to add my personal thanks to everyone whose contributions - both past and ongoing - have helped FROST reach this stage.
This is a significant step, both in terms of progress towards making FROST signatures available for use with Zcash, and for the broader cause of financial privacy.
FROST is a significant cryptographic innovation in its own right (which is why it has attracted the CFRG’s interest), and has applications beyond cryptocurrency. For Zcash specifically, it brings a number of benefits.
While transparent ZEC can be protected using Bitcoin-style multisig, that doesn’t work for shielded ZEC, which means that shielded ZEC can’t address use cases that require that spend transactions are authorised by k of n keys (e.g. custody).
FROST for Zcash will fix that, thus fulfilling a key prerequisite for deprecating t-addresses.
It also has future uses in bridging ZEC to other chains, and, once ZSAs are implemented, bridging other assets to Zcash, as well as enabling k-of-n authorisation for asset issuance.
Beyond enabling specific use cases, FROST is more flexible than multisig. For example, a lost share can be recovered whereas, if a multisig keyholder loses their key, there’s no way to recover it (e.g. a 2-of-3 multisig would become a 2-of-2 multisig).
In short, FROST is cool.