The verifier's check in the inner product argument used to assume that the
G'_0 value had an additional (trivial) blinding factor term, which makes
it slightly easier to reason that it never is the point at infinity.
However, we never sample challenges that are zeroes (both for security
and completeness reasons) so this element would never be the point at
infinity anyway. Thus, we can simplify the check with the added benefit of
matching the book's description of the protocol.
This changes variable names in the multiopen and commitment opening implementations
and the book's protocol description to keep names and indicies consistent with one
another.
Co-Authored-By: Jack Grigg <jack@electriccoin.co>
Previously `plonk::verify_proof` took an `MSM` as an argument, to enable
batch verification. However, this also required that it take a source of
randomness in order to enforce separation of proofs within a batch. This
made single-proof verification unnecessarily non-deterministic.
We now have a `VerificationStrategy` trait encapsulating the necessary
details, and separate `SingleVerifier` and `BatchVerifier` structs for
the specific variants. Proof verifiers no longer need to create and
manage the `MSM` themselves, and single-proof verifiers no longer need
to supply a source of randomness.
Co-authored-by: Sean Bowe <sean@electriccoin.co>
Previously we were passing through the chunk size and index to each
thread's evaluation context, but this was insufficient for them to
determine whether or not they were processing the final chunk, or if
the final chunk was short. This led to constant and linear term chunks
being created with the full chunk size, even if the last chunk was
short. If this longer-than-short chunk reached the root of the AST, it
triggered a panic in the final `copy_from_slice()`.
The bug was obscured in two ways:
- Currently polynomials always have a power-of-two length, and on CPUs
with power-of-two threads this meant we never produced short chunks.
- The way that subsequent operations like `Ast::Add` were implemented
meant that if a constant or linear term occurred on the right-hand
side of an operation, the longer chunks were masked to the short chunk
length.
We fix this by passing the polynomial length into each thread's context,
so that we can compute the correct length for the final chunk.
Co-authored-by: Daira Hopwood <daira@jacaranda.org>
Jack Grigg
Sean Bowe
Dimitris Apostolou