moves verify.rs to examples and adds comments about safety

phase2/src/utils.rs

@@ -104,7 +104,7 @@ pub fn merge_pairs<G: CurveAffine>(v1: &[G], v2: &[G]) -> (G, G)
 
 
 /// Hashes to G2 using the first 32 bytes of `digest`. Panics if `digest` is less
-/// than 32 bytes.
+/// than 32 bytes. The input must be random.
 pub fn hash_to_g2(mut digest: &[u8]) -> G2
 {
     assert!(digest.len() >= 32);
@@ -179,4 +179,4 @@ pub fn pairing_to_vec(p: &Fq12) -> Vec<Vec<Vec<String>>> {
             ]
         ],
     ]
-}
+}

powersoftau/examples/verify.rs

@@ -1,3 +1,7 @@
+//! verify.rs has multiple problems and shouldn't be used in production without further changes.
+//! Specifically, it doesn't verify the hash chain from each of the contributions and it has a
+//! hardcoded number of participants.
+
 use bellman_ce::pairing::bn256::Bn256;
 use bellman_ce::pairing::bn256::{G1, G2};
 use bellman_ce::pairing::{CurveAffine, CurveProjective};

powersoftau/src/utils.rs

@@ -27,7 +27,7 @@ pub fn calculate_hash(input_map: &Mmap) -> GenericArray<u8, U64> {
 }
 
 /// Hashes to G2 using the first 32 bytes of `digest`. Panics if `digest` is less
-/// than 32 bytes.
+/// than 32 bytes. The input must be random.
 pub fn hash_to_g2<E: Engine>(mut digest: &[u8]) -> E::G2 {
     assert!(digest.len() >= 32);