mpc: templatize implementations

clearmatics · Aug 29, 2019 · 9718bb9 · 9718bb9
1 parent 65def7d
commit 9718bb9
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Showing 3 changed files with 34 additions and 25 deletions.
diff --git a/src/snarks/groth16/mpc_utils.hpp b/src/snarks/groth16/mpc_utils.hpp
@@ -24,11 +24,9 @@
 namespace libzeth
 {
 
-using ppT = libff::default_ec_pp;
-
 /// Output from linear combination $L_1$ - the linear combination of
 /// elements in powersoftau, based on a specific circuit.
-class srs_mpc_layer_L1
+template<typename ppT> class srs_mpc_layer_L1
 {
 public:
     /// { [ t(x) . x^i ]_1 }  i = 0 .. n-1
@@ -57,20 +55,24 @@ class srs_mpc_layer_L1
 /// Given a circuit and a powersoftau with pre-computed lagrange
 /// polynomials, perform the correct linear combination for the CRS
 /// MPC.
-srs_mpc_layer_L1 mpc_compute_linearcombination(
+template<typename ppT>
+srs_mpc_layer_L1<ppT> mpc_compute_linearcombination(
     const powersoftau &pot, const libsnark::qap_instance<libff::Fr<ppT>> &qap);
 
 /// Given the output from the first layer of the MPC, perform the 2nd
 /// layer computation using just local randomness.  This is not a
 /// substitute for the full MPC with an auditable log of
 /// contributions, but is useful for testing.
+template<typename ppT>
 libsnark::r1cs_gg_ppzksnark_keypair<ppT> mpc_dummy_layer2(
     powersoftau &&pot,
-    srs_mpc_layer_L1 &&layer1,
+    srs_mpc_layer_L1<ppT> &&layer1,
     const libff::Fr<ppT> &delta,
     libsnark::r1cs_constraint_system<libff::Fr<ppT>> &&cs,
     const libsnark::qap_instance<libff::Fr<ppT>> &qap);
 
 } // namespace libzeth
 
+#include "snarks/groth16/mpc_utils.tcc"
+
 #endif // __ZETH_SNARKS_GROTH16_MPC_UTILS_HPP__
diff --git a/src/snarks/groth16/mpc_utils.cpp → src/snarks/groth16/mpc_utils.tcc b/src/snarks/groth16/mpc_utils.cpp → src/snarks/groth16/mpc_utils.tcc
@@ -1,23 +1,17 @@
-#include "mpc_utils.hpp"
+#ifndef __ZETH_SNARKS_GROTH16_MPC_UTILS_TCC__
+#define __ZETH_SNARKS_GROTH16_MPC_UTILS_TCC__
 
 #include "evaluator_from_lagrange.hpp"
+#include "mpc_utils.hpp"
 #include "multi_exp.hpp"
 
 #include <libff/algebra/scalar_multiplication/multiexp.hpp>
 
 namespace libzeth
 {
 
-using ppT = libff::default_ec_pp;
-using Fr = libff::Fr<ppT>;
-using G1 = libff::G1<ppT>;
-using G2 = libff::G2<ppT>;
-
-// -----------------------------------------------------------------------------
-// srs_mpc_layer_L1
-// -----------------------------------------------------------------------------
-
-srs_mpc_layer_L1::srs_mpc_layer_L1(
+template<typename ppT>
+srs_mpc_layer_L1<ppT>::srs_mpc_layer_L1(
     libff::G1_vector<ppT> &&T_tau_powers_g1,
     libff::G1_vector<ppT> &&A_g1,
     libff::G1_vector<ppT> &&B_g1,
@@ -31,9 +25,14 @@ srs_mpc_layer_L1::srs_mpc_layer_L1(
 {
 }
 
-srs_mpc_layer_L1 mpc_compute_linearcombination(
-    const powersoftau &pot, const libsnark::qap_instance<Fr> &qap)
+template<typename ppT>
+srs_mpc_layer_L1<ppT> mpc_compute_linearcombination(
+    const powersoftau &pot, const libsnark::qap_instance<libff::Fr<ppT>> &qap)
 {
+    using Fr = libff::Fr<ppT>;
+    using G1 = libff::G1<ppT>;
+    using G2 = libff::G2<ppT>;
+
     libfqfft::evaluation_domain<Fr> &domain = *qap.domain;
 
     // n = number of constraints in qap / degree of t().
@@ -116,21 +115,26 @@ srs_mpc_layer_L1 mpc_compute_linearcombination(
     // by this circuit and using sparse vectors where it makes sense
     // (as is done for B_i's in r1cs_gg_ppzksnark_proving_key).
 
-    return srs_mpc_layer_L1(
+    return srs_mpc_layer_L1<ppT>(
         std::move(t_x_pow_i),
         std::move(A_i_g1),
         std::move(B_i_g1),
         std::move(B_i_g2),
         std::move(ABC_i_g1));
 }
 
+template<typename ppT>
 libsnark::r1cs_gg_ppzksnark_keypair<ppT> mpc_dummy_layer2(
     powersoftau &&pot,
-    srs_mpc_layer_L1 &&layer1,
-    const Fr &delta,
-    libsnark::r1cs_constraint_system<Fr> &&cs,
-    const libsnark::qap_instance<Fr> &qap)
+    srs_mpc_layer_L1<ppT> &&layer1,
+    const libff::Fr<ppT> &delta,
+    libsnark::r1cs_constraint_system<libff::Fr<ppT>> &&cs,
+    const libsnark::qap_instance<libff::Fr<ppT>> &qap)
 {
+    using Fr = libff::Fr<ppT>;
+    using G1 = libff::G1<ppT>;
+    using G2 = libff::G2<ppT>;
+
     const Fr delta_inverse = delta.inverse();
 
     // { H_i } = { [ t(x) . x^i / delta ]_i } i = 0 .. m-1
@@ -200,3 +204,5 @@ libsnark::r1cs_gg_ppzksnark_keypair<ppT> mpc_dummy_layer2(
 }
 
 } // namespace libzeth
+
+#endif // __ZETH_SNARKS_GROTH16_MPC_UTILS_TCC__
diff --git a/src/test/mpc_test.cpp b/src/test/mpc_test.cpp
@@ -36,7 +36,8 @@ TEST(MPCTests, LinearCombination)
         dummy_powersoftau_from_secrets(tau, alpha, beta, qap.degree());
 
     // linear combination
-    const srs_mpc_layer_L1 layer1 = mpc_compute_linearcombination(pot, qap);
+    const srs_mpc_layer_L1<ppT> layer1 =
+        mpc_compute_linearcombination<ppT>(pot, qap);
 
     // Without knowlege of tau, not many checks can be performed
     // beyond the ratio of terms in [ t(x) . x^i ]_1.
@@ -113,7 +114,7 @@ TEST(MPCTests, Layer2)
     size_t num_variables = qap.num_variables();
     size_t num_inputs = qap.num_inputs();
 
-    srs_mpc_layer_L1 layer1 = mpc_compute_linearcombination(pot, qap);
+    srs_mpc_layer_L1<ppT> layer1 = mpc_compute_linearcombination<ppT>(pot, qap);
 
     // Final key pair
     const r1cs_gg_ppzksnark_keypair<ppT> keypair = mpc_dummy_layer2(