Fixes the build

[gtank]

These seem recent as of (variously) Rust 1.53 and 1.54. They were causing the style check to break the build.

[gtank]

Oh, come on!

[gtank]

The code needs several fixes.

• A package moved https://github.com/arkworks-rs/std/pull/29
• There's a security vuln that requires the 0.3.x branch of the arkworks packages to fix https://rustsec.org/advisories/RUSTSEC-2021-0075
• 0.3.x contains a breaking API change that affects one of our hashers (FixedLengthCRH -> CRH -> CRHScheme depending on how up to date we want to be. Note also that trait may not imply fixed length in the future.) https://github.com/arkworks-rs/crypto-primitives/pull/30

Upgrading to anything past our pinned version also causes a build error I can't figure out how to fix at the moment:

error[E0277]: the trait bound `ark_bls12_377::Parameters: Bls12Parameters` is not satisfied
  --> crates/bls-crypto/src/hash_to_curve/try_and_increment.rs:31:43
   |
31 |     TryAndIncrement<CompositeHasher<CRH>, <Parameters as Bls12Parameters>::G1Parameters>,
   |                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Bls12Parameters` is not implemented for `ark_bls12_377::Parameters`
   |
  ::: /Users/gtank/.cargo/git/checkouts/algebra-7e23afa68841b66e/344b27d/ec/src/models/bls12/mod.rs:30:1
   |
30 | pub trait Bls12Parameters: 'static {
   | ---------------------------------- required by this bound in `Bls12Parameters`

error[E0277]: the trait bound `ark_bls12_377::Parameters: Bls12Parameters` is not satisfied
  --> crates/bls-crypto/src/hash_to_curve/try_and_increment.rs:37:35
   |
37 |     TryAndIncrement<DirectHasher, <Parameters as Bls12Parameters>::G1Parameters>,
   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Bls12Parameters` is not implemented for `ark_bls12_377::Parameters`
   |
  ::: /Users/gtank/.cargo/git/checkouts/algebra-7e23afa68841b66e/344b27d/ec/src/models/bls12/mod.rs:30:1
   |
30 | pub trait Bls12Parameters: 'static {
   | ---------------------------------- required by this bound in `Bls12Parameters`

error[E0277]: the trait bound `ark_bls12_377::Parameters: Bls12Parameters` is not satisfied
  --> crates/bls-crypto/src/hash_to_curve/try_and_increment_cip22.rs:31:48
   |
31 |     TryAndIncrementCIP22<CompositeHasher<CRH>, <Parameters as Bls12Parameters>::G1Parameters>,
   |                                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Bls12Parameters` is not implemented for `ark_bls12_377::Parameters`
   |
  ::: /Users/gtank/.cargo/git/checkouts/algebra-7e23afa68841b66e/344b27d/ec/src/models/bls12/mod.rs:30:1
   |
30 | pub trait Bls12Parameters: 'static {
   | ---------------------------------- required by this bound in `Bls12Parameters`

For more information about this error, try `rustc --explain E0277`.
error: could not compile `bls-crypto` due to 3 previous errors
warning: build failed, waiting for other jobs to finish...
error: build failed

[gtank]

Due to the risk of semantically important circuit changes, we're going to hang on to our 0.1.0 arkworks version. Conversation elsewhere with @kobigurk established that RUSTSEC-2021-0075 doesn't affect us here.

[kobigurk]

To be concrete, the commit we have in Cargo.lock is the one that we used for creating the circuit and that we've matched against.

On Wed, Sep 15, 2021 at 7:59 PM George Tankersley @.***> wrote:

Due to the risk of semantically important circuit changes, we're going to hang on to our 0.1.0 arkworks version. Conversation elsewhere with @kobigurk https://github.com/kobigurk established that RUSTSEC-2021-0075 doesn't affect us here.

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/celo-org/celo-bls-snark-rs/pull/225#issuecomment-920201504, or unsubscribe https://github.com/notifications/unsubscribe-auth/AA23MGG2WZCPBB6HTSFSHH3UCDGILANCNFSM5EBJ2HIQ .

[gtank]

To be even more concrete, our pinned version predates the bug addressed in RUSTSEC-2021-0075, which was introduced in https://github.com/arkworks-rs/r1cs-std/commit/f88d7c6ea336d4b71e52f53c6ae2934e29accf43 and resolved in https://github.com/arkworks-rs/r1cs-std/commit/b6e7e94521854edd7a4892a61419202b0784eb0b.

Further discussion (h/t @kobigurk):

• The relevant implementation in our case would also be the one for FieldVar, from the relevant values being QuadExtVar, which does check the full relation (https://github.com/arkworks-rs/r1cs-std/blob/e5ec2e66d3aead34f7e3fa15909f22e1600bd11d/src/fields/mod.rs#L162).
• We can be confident that our inputs wouldn't be zero because they come from a sum of public keys that have been checked against a hash.