Change point generator to accept range and properly fix issue from previous commit

Signed-off-by: lovesh <lovesh.bond@gmail.com>

Author: lovesh

bbs_plus/src/setup.rs

@@ -258,9 +258,9 @@ macro_rules! impl_sig_params {
                             &concat_slices!(label, b" : g1"),
                         );
                         let h_bytes = concat_slices!(label, b" : h_");
-                        // h_0 and h[i] for i in 1 to message_count
+                        // h_i for i in 0 to message_count
                         let h = n_projective_group_elements::<E::$group_affine, D>(
-                            1 + message_count,
+                            0..message_count + 1,
                             &h_bytes,
                         );
                         let g1_and_h: Vec<_> = iter::once(g1).chain(h).collect();
@@ -523,13 +523,11 @@ impl<E: Pairing> SignatureParams23G1<E> {
             affine_group_element_from_byte_slices!(label, b" : g1"),
             affine_group_element_from_byte_slices!(label, b" : g2"),
             {
-                let mut h: Vec<_> = n_projective_group_elements::<E::G1Affine, D>(
-                    1 + message_count,
+                let h: Vec<_> = n_projective_group_elements::<E::G1Affine, D>(
+                    1..message_count + 1,
                     &concat_slices!(label, b" : h_"),
                 )
                 .collect();
-                // TODO: Fix me by making above point generator accept a range
-                h.remove(0);
                 E::G1::normalize_batch(&h)
             }
         );

coconut/src/setup/signature_params.rs

@@ -38,7 +38,7 @@ impl<E: Pairing> SignatureParams<E> {
         let (g, g_tilde, h) = join!(
             affine_group_element_from_byte_slices!(label, b" : g"),
             affine_group_element_from_byte_slices!(label, b" : g_tilde"),
-            n_affine_group_elements::<_, D>(message_count, &concat_slices!(label, b" : h_"))
+            n_affine_group_elements::<_, D>(0..message_count, &concat_slices!(label, b" : h_"))
                 .collect()
         );
 

utils/src/misc.rs

@@ -79,23 +79,30 @@ pub fn le_bytes_iter(n: u32) -> impl_indexed_iter!(<Item = [u8; 4]>) {
     cfg_into_iter!(0..n).map(u32::to_le_bytes)
 }
 
-/// Produces `n` projective group elements by combining the supplied bytes with the `u32::to_le_bytes` counter bytes.
+/// Produces an iterator of little endian bytes of each element contained in the range `counter_range`
+pub fn le_bytes_iter_from_given_range(
+    counter_range: Range<u32>,
+) -> impl_indexed_iter!(<Item = [u8; 4]>) {
+    cfg_into_iter!(counter_range).map(u32::to_le_bytes)
+}
+
+/// Produces an iterator of projective group elements created by hashing a label and a counter in the range `counter_range`
 pub fn n_projective_group_elements<'iter, G, D>(
-    n: u32,
+    counter_range: Range<u32>,
     bytes: &'iter [u8],
 ) -> impl_indexed_iter!(<Item = G::Group> + 'iter)
 where
     G: AffineRepr + SendIfParallel,
     D: Digest,
 {
-    le_bytes_iter(n).map(move |ctr_bytes| -> G::Group {
+    le_bytes_iter_from_given_range(counter_range).map(move |ctr_bytes| -> G::Group {
         projective_group_elem_from_try_and_incr::<G, D>(&concat_slices!(bytes.as_ref(), ctr_bytes))
     })
 }
 
-/// Produces `n` affine group elements by combining the supplied bytes with the `u32::to_le_bytes` counter bytes.
+/// Produces an iterator affine group elements created by hashing a label and a counter in the range `counter_range`
 pub fn n_affine_group_elements<'iter, G, D>(
-    n: u32,
+    n: Range<u32>,
     bytes: &'iter [u8],
 ) -> impl_indexed_iter!(<Item = G> + 'iter)
 where