Add cap size to BCS parameters

Author: alexander-zw

libiop/bcs/bcs_common.hpp

@@ -25,6 +25,7 @@ template<typename FieldT, typename MT_hash_type>
 struct bcs_transformation_parameters {
     std::size_t security_parameter; /* TODO: possibly revisit in the future */
     bcs_hash_type hash_enum;
+    std::size_t cap_size;
 
     pow_parameters pow_params_;
 

libiop/bcs/bcs_common.tcc

@@ -474,7 +474,8 @@ void bcs_protocol<FieldT, MT_root_hash>::seal_interaction_registrations()
                 this->parameters_.cap_hasher,
                 this->digest_len_bytes_,
                 make_zk,
-                this->parameters_.security_parameter);
+                this->parameters_.security_parameter,
+                this->parameters_.cap_size);
             this->Merkle_trees_.emplace_back(MT);
         }
     }

libiop/bcs/common_bcs_parameters.tcc

@@ -15,6 +15,7 @@ bcs_transformation_parameters<FieldT, MT_root_hash> default_bcs_params(
     params.hash_enum = hash_type;
     /* TODO: Push setting leaf hash into internal BCS code. Currently 2 is fine, as leaf size is internally unused. */
     const size_t leaf_size = 2;
+    params.cap_size = 2;
     params.leafhasher_ = get_leafhash<MT_root_hash, FieldT>(hash_type, security_parameter, leaf_size);
     params.compression_hasher = get_two_to_one_hash<MT_root_hash, FieldT>(hash_type, security_parameter);
     params.cap_hasher = get_cap_hash<MT_root_hash, FieldT>(hash_type, security_parameter);

libiop/tests/bcs/test_bcs_transformation.cpp

@@ -72,6 +72,7 @@ bcs_transformation_parameters<FieldT, MT_root_hash> get_bcs_parameters(bool alge
         bcs_parameters.hash_enum = bcs_hash_type::blake2b_type;
     }
     set_bcs_parameters_leafhash<FieldT, MT_root_hash>(bcs_parameters);
+    bcs_parameters.cap_size = 2;
 
     return bcs_parameters;
 }