2 commits

Author	SHA1	Message	Date
Luke Parker	251a6e96e8	Constant-time divisors (#617) ... * WIP constant-time implementation of the ec-divisors library * Fix misc logic errors in poly.rs * Remove accidentally committed test statements * Fix ConstantTimeEq for CoefficientIndex * Correct the iterations formula x**3 / (0 y + x**1) would prior be considered indivisible with iterations = 0. It is divisible however. The amount of iterations should be the amount of coefficients within the numerator *excluding the coefficient for y**0 x**0*. * Poly PartialEq, conditional_select_poly which checks poly structure equivalence If the first passed argument is smaller than the latter, it's padded to the necessary length. Also adds code to trim the remainder as the remainder is the value modulo, so it's very important it remains concise and workable. * Fix the line function It selected the case if both were identity before selecting the case if either were identity, the latter overwriting the former. * Final fixes re: ct_get 1) Our quotient structure does need to be of size equal to the numerator entirely to prevent out-of-bounds reads on it 2) We need to get from yx_coefficients if of length >=, so if the length is 1 we can read y_pow=1 from it. If y_pow=0, and its length is 0 so it has no inner Vecs, we need to fall back with the guard y_pow != 0. * Add a trim algorithm to lib.rs to prevent Polys from becoming unbearably gigantic Our Poly algorithm is incredibly leaky. While it presumably should be improved, we can take advantage of our known structure while constructing divisors (and the small modulus) to simply trim out the zero coefficients leaked. This maintains Polys in a manageable size. * Move constant-time scalar mul gadget divisor creation from dkg to ec-divisors Anyone creating a divisor for the scalar mul gadget should use constant time code, so this code should at least be in the EC gadgets crate It's of non-trivial complexity to deal with otherwise. * Remove unsafe, cache timing attacks from ec-divisors	2024-09-24 17:27:05 -04:00
Luke Parker	e4e4245ee3	One Round DKG (#589) ... * Upstream GBP, divisor, circuit abstraction, and EC gadgets from FCMP++ * Initial eVRF implementation Not quite done yet. It needs to communicate the resulting points and proofs to extract them from the Pedersen Commitments in order to return those, and then be tested. * Add the openings of the PCs to the eVRF as necessary * Add implementation of secq256k1 * Make DKG Encryption a bit more flexible No longer requires the use of an EncryptionKeyMessage, and allows pre-defined keys for encryption. * Make NUM_BITS an argument for the field macro * Have the eVRF take a Zeroizing private key * Initial eVRF-based DKG * Add embedwards25519 curve * Inline the eVRF into the DKG library Due to how we're handling share encryption, we'd either need two circuits or to dedicate this circuit to the DKG. The latter makes sense at this time. * Add documentation to the eVRF-based DKG * Add paragraph claiming robustness * Update to the new eVRF proof * Finish routing the eVRF functionality Still needs errors and serialization, along with a few other TODOs. * Add initial eVRF DKG test * Improve eVRF DKG Updates how we calculcate verification shares, improves performance when extracting multiple sets of keys, and adds more to the test for it. * Start using a proper error for the eVRF DKG * Resolve various TODOs Supports recovering multiple key shares from the eVRF DKG. Inlines two loops to save 2**16 iterations. Adds support for creating a constant time representation of scalars < NUM_BITS. * Ban zero ECDH keys, document non-zero requirements * Implement eVRF traits, all the way up to the DKG, for secp256k1/ed25519 * Add Ristretto eVRF trait impls * Support participating multiple times in the eVRF DKG * Only participate once per key, not once per key share * Rewrite processor key-gen around the eVRF DKG Still a WIP. * Finish routing the new key gen in the processor Doesn't touch the tests, coordinator, nor Substrate yet. `cargo +nightly fmt && cargo +nightly-2024-07-01 clippy --all-features -p serai-processor` does pass. * Deduplicate and better document in processor key_gen * Update serai-processor tests to the new key gen * Correct amount of yx coefficients, get processor key gen test to pass * Add embedded elliptic curve keys to Substrate * Update processor key gen tests to the eVRF DKG * Have set_keys take signature_participants, not removed_participants Now no one is removed from the DKG. Only `t` people publish the key however. Uses a BitVec for an efficient encoding of the participants. * Update the coordinator binary for the new DKG This does not yet update any tests. * Add sensible Debug to key_gen::[Processor, Coordinator]Message * Have the DKG explicitly declare how to interpolate its shares Removes the hack for MuSig where we multiply keys by the inverse of their lagrange interpolation factor. * Replace Interpolation::None with Interpolation::Constant Allows the MuSig DKG to keep the secret share as the original private key, enabling deriving FROST nonces consistently regardless of the MuSig context. * Get coordinator tests to pass * Update spec to the new DKG * Get clippy to pass across the repo * cargo machete * Add an extra sleep to ensure expected ordering of `Participation`s * Update orchestration * Remove bad panic in coordinator It expected ConfirmationShare to be n-of-n, not t-of-n. * Improve documentation on functions * Update TX size limit We now no longer have to support the ridiculous case of having 49 DKG participations within a 101-of-150 DKG. It does remain quite high due to needing to _sign_ so many times. It'd may be optimal for parties with multiple key shares to independently send their preprocesses/shares (despite the overhead that'll cause with signatures and the transaction structure). * Correct error in the Processor spec document * Update a few comments in the validator-sets pallet * Send/Recv Participation one at a time Sending all, then attempting to receive all in an expected order, wasn't working even with notable delays between sending messages. This points to the mempool not working as expected... * Correct ThresholdKeys serialization in modular-frost test * Updating existing TX size limit test for the new DKG parameters * Increase time allowed for the DKG on the GH CI * Correct construction of signature_participants in serai-client tests Fault identified by akil. * Further contextualize DkgConfirmer by ValidatorSet Caught by a safety check we wouldn't reuse preprocesses across messages. That raises the question of we were prior reusing preprocesses (reusing keys)? Except that'd have caused a variety of signing failures (suggesting we had some staggered timing avoiding it in practice but yes, this was possible in theory). * Add necessary calls to set_embedded_elliptic_curve_key in coordinator set rotation tests * Correct shimmed setting of a secq256k1 key * cargo fmt * Don't use `[0; 32]` for the embedded keys in the coordinator rotation test The key_gen function expects the random values already decided. * Big-endian secq256k1 scalars Also restores the prior, safer, Encryption::register function.	2024-09-19 21:43:26 -04:00