adds hash_type to ec_point_util

4 files changed, 24 insertions, 5 deletions

diff --git a/crypto/BUILD b/crypto/BUILD
index 94e186f..58656be 100644
--- a/crypto/BUILD
+++ b/crypto/BUILD
@@ -140,6 +140,7 @@ cc_library(
     ],
     deps = [
         ":bn_util",
+        ":ec_commutative_cipher",
         ":ec_util",
         "//util:status_includes",
         "@com_github_glog_glog//:glog",
diff --git a/crypto/ec_commutative_cipher.h b/crypto/ec_commutative_cipher.h
index 09b3a2d..c5f840d 100644
--- a/crypto/ec_commutative_cipher.h
+++ b/crypto/ec_commutative_cipher.h
@@ -87,7 +87,8 @@ namespace private_join_and_compute {
 
 class ECCommutativeCipher {
  public:
-  // The hash function used by the ECCommutativeCipher.
+  // The hash function used by the ECCommutativeCipher in order to hash strings
+  // to EC curve points. The suggested default is the SHA256 option.
   enum HashType {
     SHA256,
     SHA512,
diff --git a/crypto/ec_point_util.cc b/crypto/ec_point_util.cc
index 494b975..784c7a8 100644
--- a/crypto/ec_point_util.cc
+++ b/crypto/ec_point_util.cc
@@ -23,6 +23,7 @@
 #include "crypto/ec_group.h"
 #include "crypto/ec_point.h"
 #include "util/status.inc"
+#include "crypto/ec_commutative_cipher.h"
 #include "absl/strings/string_view.h"
 
 namespace private_join_and_compute {
@@ -43,9 +44,21 @@ StatusOr<std::string> ECPointUtil::GetRandomCurvePoint() {
   return point.ToBytesCompressed();
 }
 
-StatusOr<std::string> ECPointUtil::HashToCurve(absl::string_view input) {
-  ASSIGN_OR_RETURN(ECPoint point, group_.GetPointByHashingToCurveSha512(input));
-  return point.ToBytesCompressed();
+StatusOr<std::string> ECPointUtil::HashToCurve(
+    absl::string_view input, ECCommutativeCipher::HashType hash_type) {
+  if (hash_type == ECCommutativeCipher::HashType::SHA512) {
+    ASSIGN_OR_RETURN(ECPoint point,
+                     group_.GetPointByHashingToCurveSha512(input));
+    return point.ToBytesCompressed();
+  }
+
+  if (hash_type == ECCommutativeCipher::HashType::SHA256) {
+    ASSIGN_OR_RETURN(ECPoint point,
+                     group_.GetPointByHashingToCurveSha256(input));
+    return point.ToBytesCompressed();
+  }
+
+  return InvalidArgumentError("Invalid hash type.");
 }
 
 bool ECPointUtil::IsCurvePoint(absl::string_view input) {
diff --git a/crypto/ec_point_util.h b/crypto/ec_point_util.h
index ef2b53c..467c80c 100644
--- a/crypto/ec_point_util.h
+++ b/crypto/ec_point_util.h
@@ -25,6 +25,7 @@
 #include "crypto/ec_group.h"
 #include "crypto/ec_point.h"
 #include "util/status.inc"
+#include "crypto/ec_commutative_cipher.h"
 #include "absl/strings/string_view.h"
 
 namespace private_join_and_compute {
@@ -47,7 +48,10 @@ class ECPointUtil {
   StatusOr<std::string> GetRandomCurvePoint();
 
   // Hashes the given string to the curve.
-  StatusOr<std::string> HashToCurve(absl::string_view input);
+  //
+  // Suggested default hash_type is ECCommutativeCipher::HashType::Sha256.
+  StatusOr<std::string> HashToCurve(absl::string_view input,
+                                    ECCommutativeCipher::HashType hash_type);
 
   // Checks if a string represents a curve point.
   // May give a false negative if an internal error occurs.