partially blind signatures

src/main/java/edu/jhu/isi/CLSign/CLSign.java

@@ -21,10 +21,10 @@
  */
 package edu.jhu.isi.CLSign;
 
-import edu.jhu.isi.CLSign.entities.KeyPair;
-import edu.jhu.isi.CLSign.entities.PublicKey;
-import edu.jhu.isi.CLSign.entities.SecretKey;
-import edu.jhu.isi.CLSign.entities.Signature;
+import edu.jhu.isi.CLSign.keygen.KeyPair;
+import edu.jhu.isi.CLSign.keygen.PublicKey;
+import edu.jhu.isi.CLSign.keygen.SecretKey;
+import edu.jhu.isi.CLSign.sign.Signature;
 import edu.jhu.isi.CLSign.keygen.KeyGen;
 import edu.jhu.isi.CLSign.sign.Sign;
 import edu.jhu.isi.CLSign.verify.Verify;
@@ -43,11 +43,17 @@ public class CLSign {
     }
 
     public static Element commit(final List<ZrElement> messages, final PublicKey pk) {
-        Element commitment = pk.getGenerator().powZn(messages.get(0));
-        for (int i = 1; i < messages.size(); i++) {
-            commitment = commitment.mul(pk.getZ(i).powZn(messages.get(i)));
+        if (messages.size() != pk.getZ().size()) {
+            throw new IllegalStateException("Public key should be generated with the correct message size");
         }
-        return commitment.getImmutable();
+        return doCommit(messages, pk);
+    }
+
+    public static Element partialCommit(final List<ZrElement> messages, final PublicKey pk) {
+        if (messages.size() > pk.getZ().size()) {
+            throw new IllegalStateException("Public key should be generated with a larger message size");
+        }
+        return doCommit(messages, pk);
     }
 
     public static Signature sign(final List<ZrElement> messages, final KeyPair keys) {
@@ -59,9 +65,27 @@ public class CLSign {
         return Sign.sign(commitment, keys);
     }
 
+    public static Signature signPartiallyBlind(final List<ZrElement> messages, final Element commitment, final KeyPair keys) {
+        final List<Element> Z = keys.getPk().getZ();
+        final List<Element> subKey = Z.subList(Z.size() - messages.size(), Z.size());
+        final Element extendCommitment = keys.getPk().getPairing().getG1().newOneElement();
+        for (int i = 0; i < messages.size(); i++) {
+            extendCommitment.mul(subKey.get(i).powZn(messages.get(i)));
+        }
+        return Sign.sign(commitment.mul(extendCommitment), keys);
+    }
+
     public static boolean verify(final List<ZrElement> messages, final Signature sigma, final PublicKey pk) {
         return Verify.aFormedCorrectly(sigma, pk)
                 && Verify.bFormedCorrectly(sigma, pk)
                 && Verify.cFormedCorrectly(messages, sigma, pk);
     }
+
+    private static Element doCommit(final List<ZrElement> messages, final PublicKey pk) {
+        Element commitment = pk.getGenerator().powZn(messages.get(0));
+        for (int i = 1; i < messages.size(); i++) {
+            commitment = commitment.mul(pk.getZ(i).powZn(messages.get(i)));
+        }
+        return commitment.getImmutable();
+    }
 }

src/main/java/edu/jhu/isi/CLSign/keygen/KeyGen.java

 package edu.jhu.isi.CLSign.keygen;
 
-import edu.jhu.isi.CLSign.entities.PublicKey;
-import edu.jhu.isi.CLSign.entities.SecretKey;
 import it.unisa.dia.gas.jpbc.Element;
 import it.unisa.dia.gas.jpbc.Pairing;
 import it.unisa.dia.gas.jpbc.PairingParameters;

src/main/java/edu/jhu/isi/CLSign/entities/KeyPair.java → src/main/java/edu/jhu/isi/CLSign/keygen/KeyPair.java

@@ -19,7 +19,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
-package edu.jhu.isi.CLSign.entities;
+package edu.jhu.isi.CLSign.keygen;
 
 
 public class KeyPair {

src/main/java/edu/jhu/isi/CLSign/entities/PublicKey.java → src/main/java/edu/jhu/isi/CLSign/keygen/PublicKey.java

@@ -19,7 +19,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
-package edu.jhu.isi.CLSign.entities;
+package edu.jhu.isi.CLSign.keygen;
 
 import it.unisa.dia.gas.jpbc.Element;
 import it.unisa.dia.gas.jpbc.Pairing;

src/main/java/edu/jhu/isi/CLSign/entities/SecretKey.java → src/main/java/edu/jhu/isi/CLSign/keygen/SecretKey.java

@@ -19,7 +19,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
-package edu.jhu.isi.CLSign.entities;
+package edu.jhu.isi.CLSign.keygen;
 
 import it.unisa.dia.gas.plaf.jpbc.field.z.ZrElement;
 

src/main/java/edu/jhu/isi/CLSign/sign/Sign.java

 package edu.jhu.isi.CLSign.sign;
 
-import edu.jhu.isi.CLSign.entities.KeyPair;
-import edu.jhu.isi.CLSign.entities.PublicKey;
-import edu.jhu.isi.CLSign.entities.SecretKey;
-import edu.jhu.isi.CLSign.entities.Signature;
+import edu.jhu.isi.CLSign.keygen.KeyPair;
+import edu.jhu.isi.CLSign.keygen.PublicKey;
+import edu.jhu.isi.CLSign.keygen.SecretKey;
 import it.unisa.dia.gas.jpbc.Element;
 import it.unisa.dia.gas.plaf.jpbc.field.z.ZrElement;
 

src/main/java/edu/jhu/isi/CLSign/entities/Signature.java → src/main/java/edu/jhu/isi/CLSign/sign/Signature.java

@@ -19,7 +19,7 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
-package edu.jhu.isi.CLSign.entities;
+package edu.jhu.isi.CLSign.sign;
 
 import it.unisa.dia.gas.jpbc.Element;
 

src/main/java/edu/jhu/isi/CLSign/verify/Verify.java

 package edu.jhu.isi.CLSign.verify;
 
-import edu.jhu.isi.CLSign.entities.PublicKey;
-import edu.jhu.isi.CLSign.entities.Signature;
+import edu.jhu.isi.CLSign.keygen.PublicKey;
+import edu.jhu.isi.CLSign.sign.Signature;
 import it.unisa.dia.gas.jpbc.Element;
 import it.unisa.dia.gas.jpbc.Pairing;
 import it.unisa.dia.gas.plaf.jpbc.field.z.ZrElement;

src/test/java/edu/jhu/isi/CLSign/CLSignTest.java

 package edu.jhu.isi.CLSign;
 
-import edu.jhu.isi.CLSign.entities.KeyPair;
-import edu.jhu.isi.CLSign.entities.PublicKey;
-import edu.jhu.isi.CLSign.entities.SecretKey;
-import edu.jhu.isi.CLSign.entities.Signature;
+import edu.jhu.isi.CLSign.keygen.KeyPair;
+import edu.jhu.isi.CLSign.keygen.PublicKey;
+import edu.jhu.isi.CLSign.keygen.SecretKey;
+import edu.jhu.isi.CLSign.sign.Signature;
+import it.unisa.dia.gas.jpbc.Element;
 import it.unisa.dia.gas.plaf.jpbc.field.z.ZrElement;
 import org.junit.Test;
 
@@ -103,4 +104,49 @@ public class CLSignTest {
         final CLSign clSign = new CLSign();
         assertNotNull(clSign);
     }
+
+    @Test(expected = IllegalStateException.class)
+    public void testCommit_wrongMessageSize() throws Exception {
+        final int messageSize = 5;
+        final KeyPair keyPair = CLSign.keyGen(messageSize);
+        final List<ZrElement> messages = IntStream.range(0, messageSize + 1)
+                .mapToObj(i -> (ZrElement) keyPair.getPk().getPairing().getZr().newRandomElement().getImmutable())
+                .collect(Collectors.toList());
+        CLSign.commit(messages, keyPair.getPk());
+    }
+
+    @Test(expected = IllegalStateException.class)
+    public void testPartialCommit_wrongMessageSize() throws Exception {
+        final int messageSize = 5;
+        final KeyPair keyPair = CLSign.keyGen(messageSize);
+        final List<ZrElement> messages = IntStream.range(0, messageSize + 1)
+                .mapToObj(i -> (ZrElement) keyPair.getPk().getPairing().getZr().newRandomElement().getImmutable())
+                .collect(Collectors.toList());
+        CLSign.partialCommit(messages, keyPair.getPk());
+    }
+
+    @Test
+    public void testBlindSignature() throws Exception {
+        final int messageSize = 5;
+        final KeyPair keyPair = CLSign.keyGen(messageSize);
+        final List<ZrElement> messages = IntStream.range(0, messageSize)
+                .mapToObj(i -> (ZrElement) keyPair.getPk().getPairing().getZr().newRandomElement().getImmutable())
+                .collect(Collectors.toList());
+        final Element commitment = CLSign.commit(messages, keyPair.getPk());
+        final Signature sigma = CLSign.signBlind(commitment, keyPair);
+        assertTrue(CLSign.verify(messages, sigma, keyPair.getPk()));
+    }
+
+    @Test
+    public void testPartiallyBlindSignature() throws Exception {
+        final int messageSize = 5;
+        final KeyPair keyPair = CLSign.keyGen(messageSize);
+        final List<ZrElement> messages = IntStream.range(0, messageSize)
+                .mapToObj(i -> (ZrElement) keyPair.getPk().getPairing().getZr().newRandomElement().getImmutable())
+                .collect(Collectors.toList());
+        final Element partialCommitment = CLSign.partialCommit(messages.subList(0, messageSize - 2), keyPair.getPk());
+        final Signature sigma = CLSign.signPartiallyBlind(messages.subList(messageSize - 2, messageSize),
+                partialCommitment, keyPair);
+        assertTrue(CLSign.verify(messages, sigma, keyPair.getPk()));
+    }
 }
\ No newline at end of file