added test_crypto.cpp with first code for rsa blinding

Author: gittiver

CMakeLists.txt

@@ -16,6 +16,8 @@ endif()
 
 project(oc-issuer VERSION 0.0.2 LANGUAGES CXX)
 
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
 include(FetchContent)
 
 #
@@ -96,7 +98,10 @@ add_executable(${PROJECT_NAME} src/main.cpp)
 target_link_libraries(${PROJECT_NAME} PRIVATE oc-mint-lib INTERFACE tl::expected::expected)
 
 ## these are unittests that can be run on any platform
-add_executable(tests  test/test_big_int.cpp test/test.cpp)
+add_executable(tests test/test_big_int.cpp
+                     test/test_json_s8n.cpp
+                     test/test_crypto.cpp)
+                     
 target_link_libraries(tests
                       oc-mint-lib
 		      Catch2::Catch2WithMain)

test/test_crypto.cpp

@@ -0,0 +1,163 @@
+
+#include <catch2/catch_test_macros.hpp>
+
+#include "cryptlib.h"
+#include "integer.h"
+#include "nbtheory.h"
+#include "osrng.h"
+#include "rsa.h"
+#include "sha.h"
+
+#include <iostream>
+#include <stdexcept>
+
+
+CryptoPP::Integer blind_signature(unsigned char *msg,
+				size_t msg_len,
+
+				const CryptoPP::RSA::PublicKey& pub_key,
+				const CryptoPP::RSA::PrivateKey& priv_key) {
+  using namespace CryptoPP;
+  using std::cout;
+  using std::endl;
+  AutoSeededRandomPool prng;
+
+    // Convenience
+  const Integer &n = pub_key.GetModulus();
+  const Integer &e = pub_key.GetPublicExponent();
+  const Integer &d = priv_key.GetPrivateExponent();
+
+// For sizing the hashed message buffer. This should be SHA256 size.
+  const size_t sig_size = UnsignedMin(SHA256::BLOCKSIZE, n.ByteCount());
+// Scratch
+  SecByteBlock buff_1, buff_2, buff_3;
+
+  SecByteBlock orig(msg, msg_len);
+  Integer m(orig.data(), orig.size());
+  cout << "Message: " << std::hex << m << endl;
+
+  // Hash message per Rabin (1979)
+  buff_1.resize(sig_size);
+  SHA256 hash_1;
+  hash_1.CalculateTruncatedDigest(buff_1, buff_1.size(), orig, orig.size());
+
+  // H(m) as Integer
+  Integer hm(buff_1.data(), buff_1.size());
+  cout << "H(m): " << std::hex << hm << endl;
+
+  // Alice blinding
+  Integer r;
+  do {
+    r.Randomize(prng, Integer::One(), n - Integer::One());
+  } while (!RelativelyPrime(r, n));
+
+  // Blinding factor
+  Integer b = a_exp_b_mod_c(r, e, n);
+  cout << "Random: " << std::hex << b << endl;
+
+  // Alice blinded message
+  Integer mm = a_times_b_mod_c(hm, b, n);
+  cout << "Blind msg: " << std::hex << mm << endl;
+
+    // Bob sign
+  Integer ss = priv_key.CalculateInverse(prng, mm);
+  cout << "Blind sign: " << ss << endl;
+
+  return ss;
+}
+
+TEST_CASE("cryptopp", "[crypto]") {
+  using namespace CryptoPP;
+  using std::cout;
+  using std::endl;
+  using std::runtime_error;
+
+  // Bob artificially small key pair
+  AutoSeededRandomPool prng;
+  RSA::PrivateKey priv_key;
+
+  priv_key.GenerateRandomWithKeySize(prng, 64U);
+  RSA::PublicKey pub_key(priv_key);
+
+  // Convenience
+  const Integer &n = pub_key.GetModulus();
+  const Integer &e = pub_key.GetPublicExponent();
+  const Integer &d = priv_key.GetPrivateExponent();
+
+  // Print params
+  cout << "Pub mod: " << std::hex << pub_key.GetModulus() << endl;
+  cout << "Pub exp: " << std::hex << e << endl;
+  cout << "Priv mod: " << std::hex << priv_key.GetModulus() << endl;
+  cout << "Priv exp: " << std::hex << d << endl;
+
+  // For sizing the hashed message buffer. This should be SHA256 size.
+  const size_t sig_size = UnsignedMin(SHA256::BLOCKSIZE, n.ByteCount());
+
+  // Scratch
+  SecByteBlock buff_1, buff_2, buff_3;
+
+  // Alice original message to be signed by Bob
+  SecByteBlock orig((const byte *)"secret", 6U);
+  Integer m(orig.data(), orig.size());
+  cout << "Message: " << std::hex << m << endl;
+
+  // Hash message per Rabin (1979)
+  buff_1.resize(sig_size);
+  SHA256 hash_1;
+  hash_1.CalculateTruncatedDigest(buff_1, buff_1.size(), orig, orig.size());
+
+  // H(m) as Integer
+  Integer hm(buff_1.data(), buff_1.size());
+  cout << "H(m): " << std::hex << hm << endl;
+
+  // Alice blinding
+  Integer r;
+  do {
+    r.Randomize(prng, Integer::One(), n - Integer::One());
+  } while (!RelativelyPrime(r, n));
+
+  // Blinding factor
+  Integer b = a_exp_b_mod_c(r, e, n);
+  cout << "Random: " << std::hex << b << endl;
+
+  // Alice blinded message
+  Integer mm = a_times_b_mod_c(hm, b, n);
+  cout << "Blind msg: " << std::hex << mm << endl;
+
+  // Bob sign
+  Integer ss = priv_key.CalculateInverse(prng, mm);
+  cout << "Blind sign: " << ss << endl;
+
+  // Alice checks s(s'(x)) = x. This is from Chaum's paper
+  Integer c = pub_key.ApplyFunction(ss);
+  cout << "Check sign: " << c << endl;
+  if (c != mm) {
+    throw runtime_error("Alice cross-check failed");
+  }
+  // Alice remove blinding
+  Integer s = a_times_b_mod_c(ss, r.InverseMod(n), n);
+  cout << "Unblind sign: " << s << endl;
+
+  // Eve verifies
+  Integer v = pub_key.ApplyFunction(s);
+  cout << "Verify: " << std::hex << v << endl;
+
+  // Convert to a string
+  size_t req = v.MinEncodedSize();
+  buff_2.resize(req);
+  v.Encode(&buff_2[0], buff_2.size());
+
+  // Hash message per Rabin (1979)
+  buff_3.resize(sig_size);
+  SHA256 hash_2;
+  hash_2.CalculateTruncatedDigest(buff_3, buff_3.size(), orig, orig.size());
+
+  // Constant time compare
+  bool equal = buff_2.size() == buff_3.size() &&
+               VerifyBufsEqual(buff_2.data(), buff_3.data(), buff_3.size());
+
+  if (!equal) {
+    throw runtime_error("Eve verified failed");
+  }
+  cout << "Verified signature" << endl;
+}

test/test.cpp renamed to test/test_json_s8n.cpp

@@ -12,7 +12,7 @@ TEST_CASE( "PublicKey::to_json", "[to_json]" ) {
   REQUIRE( json["modulus"].dump() == "\"" + k.modulus.to_string() + "\""  );
   REQUIRE( json["public_exponent"].dump() == "\"" + k.public_exponent.to_string()+"\"" );
   REQUIRE( json["type"].dump() == "\"rsa public key\"" );
-  REQUIRE( json.keys().size() == 3 );
+  REQUIRE( json.keys().size() == 3U );
 }
 
 TEST_CASE("RequestCDDCSerial::from_string", "[from_string]") {