Add VRF proof verification / generation to the Schnorrkel wrapper

build.gradle

@@ -15,7 +15,7 @@ apply plugin: 'jacoco'
 
 allprojects {
     group = 'io.emeraldpay.polkaj'
-    version = "0.5.1-SNAPSHOT"
+    version = "0.5.2-SNAPSHOT"
 
     repositories {
         mavenLocal()

polkaj-schnorrkel/build.gradle

@@ -13,19 +13,4 @@ task compileRust(type:Exec) {
     commandLine 'cargo', 'build', '--release', '--target-dir=../../build/rust'
 }
 
-compileJava.dependsOn(compileRust)
-
-jar {
-    from("${buildDir}/rust/release") {
-        into "native/macos"
-        include '*.dylib'
-    }
-    from("${buildDir}/rust/release") {
-        into "native/linux"
-        include '*.so'
-    }
-    from("${buildDir}/rust/release") {
-        into "native/windows"
-        include '*.dll'
-    }
-}
+compileJava.dependsOn(compileRust)

polkaj-schnorrkel/src/main/java/io/emeraldpay/polkaj/merlin/TranscriptData.java

@@ -0,0 +1,59 @@
+package io.emeraldpay.polkaj.merlin;
+
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+
+/**
+ * A container class to simply hold all the necessary input data (label + messages) to construct the actual
+ * transcript on Rust's side. Think of this as "the bag of currently necessary arguments".
+ * The main idea of this class is to be easily portable to Rust using JNI.
+ * It has no usage on its own on the Java side alone.
+ */
+@SuppressWarnings({"MismatchedQueryAndUpdateOfCollection", "FieldCanBeLocal"})
+public class TranscriptData {
+    // INTENTIONALITY: Those fields being of type ArrayList is essential for the JNI mappings on the Rust side
+
+    // HACK:
+    //  Semantically, the internal representation of the domainSeparationLabel should be a single byte[]
+    //  Due to an unresolved issue with robusta (the rust lib) though,
+    //  the field mapping from byte[] doesn't work as expected, so this is the current workaround.
+    private final ArrayList<byte[]> domainSeparationLabel;
+
+    private final ArrayList<byte[]> labels;
+    private final ArrayList<byte[]> messages;
+
+    public TranscriptData(byte[] domainSeparationLabel) {
+        this.domainSeparationLabel = new ArrayList<>();
+        this.domainSeparationLabel.add(domainSeparationLabel);
+        this.labels = new ArrayList<>();
+        this.messages = new ArrayList<>();
+    }
+
+    /**
+     * Appends an ASCII encoded string message to the transcript with an ASCII encoded string label.
+     * @param label the ASCII encoded label
+     * @param message the ASCII encoded message
+     */
+    public void appendMessage(String label, String message) {
+        appendMessage(label, message.getBytes(StandardCharsets.US_ASCII));
+    }
+
+    /**
+     * Appends a message to the transcript with an ASCII encoded string label.
+     * @param label the ASCII encoded label
+     * @param message the actual message (content)
+     */
+    public void appendMessage(String label, byte[] message) {
+        appendMessage(label.getBytes(StandardCharsets.US_ASCII), message);
+    }
+
+    /**
+     * Appends a message to the transcript.
+     * @param label the label of the message
+     * @param message the actual message (content)
+     */
+    public void appendMessage(byte[] label, byte[] message) {
+        labels.add(label);
+        messages.add(message);
+    }
+}

polkaj-schnorrkel/src/main/java/io/emeraldpay/polkaj/schnorrkel/Schnorrkel.java

@@ -1,18 +1,9 @@
 package io.emeraldpay.polkaj.schnorrkel;
 
-import java.io.File;
-import java.io.IOException;
-import java.io.InputStream;
-import java.lang.invoke.MethodHandle;
-import java.lang.invoke.MethodHandles;
-import java.lang.invoke.MethodType;
-import java.lang.invoke.VarHandle;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.security.NoSuchAlgorithmException;
+import io.emeraldpay.polkaj.merlin.TranscriptData;
+
 import java.security.SecureRandom;
 import java.util.Arrays;
-import java.util.logging.MemoryHandler;
 
 /**
  * Schnorrkel implements Schnorr signature on Ristretto compressed Ed25519 points, as well as related protocols like
@@ -141,6 +132,10 @@ public static Schnorrkel getInstance() {
      */
     public abstract Schnorrkel.PublicKey derivePublicKeySoft(Schnorrkel.PublicKey base, Schnorrkel.ChainCode chainCode) throws SchnorrkelException;
 
+    public abstract boolean vrfVerify(PublicKey sk, TranscriptData transcript, VrfOutputAndProof vrfOutputAndProof);
+
+    public abstract VrfOutputAndProof vrfSign(KeyPair keyPair, TranscriptData transcript);
+
     // ====================== Supporting Classes ======================
 
     /**
@@ -248,5 +243,4 @@ public int hashCode() {
             return Arrays.hashCode(value);
         }
     }
-
 }

polkaj-schnorrkel/src/main/java/io/emeraldpay/polkaj/schnorrkel/SchnorrkelNative.java

@@ -1,5 +1,7 @@
 package io.emeraldpay.polkaj.schnorrkel;
 
+import io.emeraldpay.polkaj.merlin.TranscriptData;
+
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.file.Files;
@@ -55,6 +57,8 @@ private static byte[] encodeKeyPair(Schnorrkel.KeyPair keyPair) {
         return result;
     }
 
+    // ====================== Mapping to the Native Library ======================
+
     private static native byte[] sign(byte[] publicKey, byte[] secretKey, byte[] message);
 
     private static native byte[] keypairFromSeed(byte[] seed);
@@ -67,7 +71,9 @@ private static byte[] encodeKeyPair(Schnorrkel.KeyPair keyPair) {
 
     private static native byte[] derivePublicKeySoft(byte[] publicKey, byte[] cc);
 
-    // ====================== Mapping to the Native Library ======================
+    private static native boolean vrfVerify(byte[] publicKey, TranscriptData transcript, byte[] vrfOutput, byte[] vrfProof);
+
+    private static native byte[] vrfSign(byte[] secretKey, TranscriptData transcript);
 
     private static boolean extractAndLoadJNI() throws IOException {
         // define which of files bundled with Jar to extract
@@ -99,7 +105,6 @@ private static boolean extractAndLoadJNI() throws IOException {
 
         // extract native lib to the filesystem
         InputStream lib = Schnorrkel.class.getResourceAsStream(classpathFile);
-        System.out.println(classpathFile);
         if (lib == null) {
             System.err.println("Library " + classpathFile + " is not found in the classpath");
             return false;
@@ -109,7 +114,7 @@ private static boolean extractAndLoadJNI() throws IOException {
 
         Files.copy(lib, target);
         System.load(target.toFile().getAbsolutePath());
-        System.out.println("library " + classpathFile + " is loaded");
+        System.out.println("Library " + classpathFile + " is loaded");
 
         // setup JVM to delete files on exit, when possible
         target.toFile().deleteOnExit();
@@ -170,4 +175,28 @@ public PublicKey derivePublicKeySoft(PublicKey base, ChainCode chainCode) throws
         return new Schnorrkel.PublicKey(key);
     }
 
+    @Override
+    public boolean vrfVerify(PublicKey pk, TranscriptData transcript, VrfOutputAndProof vrfOutputAndProof) {
+        return vrfVerify(
+            pk.getPublicKey(),
+            transcript,
+            vrfOutputAndProof.getOutput(),
+            vrfOutputAndProof.getProof()
+        );
+    }
+
+    @Override
+    public VrfOutputAndProof vrfSign(KeyPair keyPair, TranscriptData transcript) {
+        byte[] vrfOutputAndProofBytes = vrfSign(keyPair.getSecretKey(), transcript);
+        final int OUTPUT_LEN = VrfOutputAndProof.OUTPUT_BYTE_LEN;
+        final int PROOF_LEN = VrfOutputAndProof.PROOF_BYTE_LEN;
+
+        // effectively, split the array
+        byte[] vrfOutput = new byte[OUTPUT_LEN];
+        byte[] vrfProof = new byte[PROOF_LEN];
+        System.arraycopy(vrfOutputAndProofBytes, 0, vrfOutput, 0, OUTPUT_LEN);
+        System.arraycopy(vrfOutputAndProofBytes, OUTPUT_LEN, vrfProof, 0, PROOF_LEN);
+
+        return VrfOutputAndProof.wrap(vrfOutput, vrfProof);
+    }
 }

polkaj-schnorrkel/src/main/java/io/emeraldpay/polkaj/schnorrkel/VrfOutputAndProof.java

@@ -0,0 +1,40 @@
+package io.emeraldpay.polkaj.schnorrkel;
+
+/**
+ * Essentially a record to hold the VRF output together with its proof.
+ */
+public class VrfOutputAndProof {
+    public static final int OUTPUT_BYTE_LEN = 32;
+    public static final int PROOF_BYTE_LEN = 64;
+
+    private final byte[] output;
+
+    private final byte[] proof;
+
+    public static VrfOutputAndProof wrap(byte[] output, byte[] proof) {
+        if (output.length != OUTPUT_BYTE_LEN) {
+            throw new IllegalArgumentException(
+                String.format("VRF output must be %d bytes (compressed ristretto point).", OUTPUT_BYTE_LEN));
+        }
+
+        if (proof.length != PROOF_BYTE_LEN) {
+            throw new IllegalArgumentException(
+                String.format("VRF proof must be %d bytes (compressed ristretto point).", PROOF_BYTE_LEN));
+        }
+
+        return new VrfOutputAndProof(output, proof);
+    }
+
+    private VrfOutputAndProof(byte[] output, byte[] proof) {
+        this.output = output;
+        this.proof = proof;
+    }
+
+    public byte[] getOutput() {
+        return output;
+    }
+
+    public byte[] getProof() {
+        return proof;
+    }
+}

polkaj-schnorrkel/src/rust/.gitignore

@@ -1,2 +1 @@
-Cargo.lock
 target/

polkaj-schnorrkel/src/rust/.vscode/settings.json

@@ -0,0 +1,5 @@
+{
+  "rust-analyzer.linkedProjects": [
+    "./Cargo.toml"
+  ]
+}