Halo achieves practical zero-knowledge recursive proof composition without the need for a trusted setup.
Recursive proof composition holds the potential for compressing unlimited amounts of computation, creating auditable distributed systems, building highly scalable blockchains and protecting privacy for all of humanity.
The concept is a proof that verifies the correctness of another instance of itself, allowing any amount of computational effort and data to produce a short proof that can be checked quickly.
Sean's discovery involves "Nested amortization"- repeatedly collapsing multiple instances of hard problems together over cycles of elliptic curves so that computational proofs can be used to reason about themselves efficiently, which eliminates the need for a trusted setup.
Nested proof composition may turn out to be an essential technique for scalable consensus mechanisms.
ECC is exploring the use of Halo for Zcash to both eliminate trusted setup and to scale Zcash at Layer 1 using nested proof composition.
Zero-knowledge proofs were envisioned by cryptographers and mathematicians in the mid 1980s as a means to prove a fact is true, without revealing anything about the fact itself.
Although zero-knowledge proof began as an abstraction, computer scientists quickly realized its applicability to many everyday uses of secrecy.
Almost 30 years later, a form of zero-knowledge proofs named zk-SNARKs were introduced in Zcash by ECC, as a means to protect users' financial privacy.
Halo might prove to be an important building block as a solution to support scalable, secure, privacy-protecting blockchains through the use of practical recursive zero-knowledge proofs.