patch r1cs-std dep to a cherry-picked version with the zero-scalar-mu…

…lt fix

Cargo.toml

@@ -10,7 +10,7 @@ ark-poly = "^0.4.0"
 ark-std = "^0.4.0"
 ark-crypto-primitives = { version = "^0.4.0", default-features = false, features = ["r1cs", "sponge", "crh"] }
 ark-relations = { version = "^0.4.0", default-features = false }
-ark-r1cs-std = { version = "^0.4.0", default-features = false }
+ark-r1cs-std = { default-features = false } # use latest version of the patch
 ark-circom = { git = "https://github.com/gakonst/ark-circom.git" }
 thiserror = "1.0"
 rayon = "1.7.0"
@@ -39,3 +39,11 @@ parallel = [
     "ark-ff/parallel",  
     "ark-poly/parallel", 
     ]
+
+# The following patch is to use a version of ark-r1cs-std compatible with
+# v0.4.0 but that includes a cherry-picked commit from after v0.4.0 which fixes
+# the in-circuit scalar multiplication of the zero point from
+# https://github.com/arkworks-rs/r1cs-std/pull/124, without including other
+# changes done between v0.4.0 and this fix which would break compatibility.
+[patch.crates-io]
+ark-r1cs-std = { git = "https://github.com/arnaucube/ark-r1cs-std-cherry-picked/" }