update readme and add size

README.md

@@ -6,6 +6,14 @@ revealing which element was downloaded. SealPIR was introduced at
 the Symposium on Security and Privacy (Oakland) in 2018. You can find
 a copy of the paper [here](https://eprint.iacr.org/2017/1142.pdf).
 
+This is a newer version of SealPIR that uses the latest version of SEAL
+and provides better serialization/deserialization of queries and responses,
+and a more streamlined code base. A drawback of this version is that ciphertexts 
+are slightly larger (due to specifics with SEAL). If you wish to use the 
+original version of SealPIR which uses an older version of SEAL and has smaller
+ciphertexts, check out the [original](https://github.com/microsoft/SealPIR/tree/original) 
+branch in this repository.
+
 # Compiling SEAL
 
 SealPIR depends on [Microsoft SEAL version 3.6.5](https://github.com/microsoft/SEAL/tree/3.6.5).

src/main.cpp

@@ -101,16 +101,17 @@ int main(int argc, char *argv[]) {
     cout << "Main: query generated" << endl;
 
     // Measure serialized query generation (useful for sending over the network)
-    stringstream stream;
+    stringstream client_stream;
+    stringstream server_stream;
     auto time_s_query_s = high_resolution_clock::now();
-    int query_size = client.generate_serialized_query(index, stream);
+    int query_size = client.generate_serialized_query(index, client_stream);
     auto time_s_query_e = high_resolution_clock::now();
     auto time_s_query_us = duration_cast<microseconds>(time_s_query_e - time_s_query_s).count();
     cout << "Main: serialized query generated" << endl;
 
     // Measure query deserialization (useful for receiving over the network)
     auto time_deserial_s = high_resolution_clock::now();
-    PirQuery query2 = server.deserialize_query(stream);
+    PirQuery query2 = server.deserialize_query(client_stream);
     auto time_deserial_e = high_resolution_clock::now();
     auto time_deserial_us = duration_cast<microseconds>(time_deserial_e - time_deserial_s).count();
     cout << "Main: query deserialized" << endl;
@@ -124,6 +125,9 @@ int main(int argc, char *argv[]) {
     auto time_server_us = duration_cast<microseconds>(time_server_e - time_server_s).count();
     cout << "Main: reply generated" << endl;
 
+    // Serialize reply (useful for sending over the network)
+    int reply_size = server.serialize_reply(reply, server_stream);
+
     // Measure response extraction
     auto time_decode_s = chrono::high_resolution_clock::now();
     vector<uint8_t> elems = client.decode_reply(reply, offset);
@@ -155,8 +159,9 @@ int main(int argc, char *argv[]) {
     cout << "Main: PIRServer query deserialization time: " << time_deserial_us << " us" << endl;
     cout << "Main: PIRServer reply generation time: " << time_server_us / 1000 << " ms" << endl;
     cout << "Main: PIRClient answer decode time: " << time_decode_us / 1000 << " ms" << endl;
-    cout << "Main: Reply num ciphertexts: " << reply.size() << endl;
     cout << "Main: Query size: " << query_size << " bytes" << endl;
+    cout << "Main: Reply num ciphertexts: " << reply.size() << endl;
+    cout << "Main: Reply size: " << reply_size << " bytes" << endl;
 
     return 0;
 }

src/pir_client.cpp

@@ -126,7 +126,7 @@ Plaintext PIRClient::decrypt(Ciphertext ct){
     return pt;
 }
 
-vector<uint8_t> PIRClient::decode_reply(PirReply reply, uint64_t offset){
+vector<uint8_t> PIRClient::decode_reply(PirReply &reply, uint64_t offset){
     Plaintext result = decode_reply(reply);
     
     uint32_t N = enc_params_.poly_modulus_degree(); 
@@ -140,7 +140,7 @@ vector<uint8_t> PIRClient::decode_reply(PirReply reply, uint64_t offset){
     return std::vector<uint8_t>(elems.begin() + offset * pir_params_.ele_size, elems.begin() + (offset + 1) * pir_params_.ele_size);
 }
 
-Plaintext PIRClient::decode_reply(PirReply reply) {
+Plaintext PIRClient::decode_reply(PirReply &reply) {
     uint32_t exp_ratio = pir_params_.expansion_ratio;
     uint32_t recursion_level = pir_params_.d;
 

src/pir_client.hpp

@@ -14,8 +14,8 @@ class PIRClient {
     PirQuery generate_query(std::uint64_t desiredIndex);
     // Serializes the query into the provided stream and returns number of bytes written
     int generate_serialized_query(std::uint64_t desiredIndex, std::stringstream &stream);
-    seal::Plaintext decode_reply(PirReply reply);
-    std::vector<uint8_t> decode_reply(PirReply reply, uint64_t offset);
+    seal::Plaintext decode_reply(PirReply &reply);
+    std::vector<uint8_t> decode_reply(PirReply &reply, uint64_t offset);
 
     seal::Plaintext decrypt(seal::Ciphertext ct);
 

src/pir_server.cpp

@@ -147,7 +147,15 @@ PirQuery PIRServer::deserialize_query(stringstream &stream) {
     return q;
 }
 
-PirReply PIRServer::generate_reply(PirQuery query, uint32_t client_id) {
+int PIRServer::serialize_reply(PirReply &reply, stringstream &stream) {
+  int output_size = 0;
+  for (int i = 0; i < reply.size(); i++){
+    output_size += reply[i].save(stream);
+  }
+  return output_size;
+}
+
+PirReply PIRServer::generate_reply(PirQuery &query, uint32_t client_id) {
 
     vector<uint64_t> nvec = pir_params_.nvec;
     uint64_t product = 1;

src/pir_server.hpp

@@ -20,7 +20,9 @@ class PIRServer {
             const seal::Ciphertext &encrypted, std::uint32_t m, uint32_t client_id);
 
     PirQuery deserialize_query(std::stringstream &stream);
-    PirReply generate_reply(PirQuery query, std::uint32_t client_id);
+    PirReply generate_reply(PirQuery &query, std::uint32_t client_id);
+    // Serializes the reply into the provided stream and returns the number of bytes written
+    int serialize_reply(PirReply &reply, std::stringstream &stream);
 
     void set_galois_key(std::uint32_t client_id, seal::GaloisKeys galkey);