Merge pull request #164 from cleishm/signature-keys-to-box

Add conversion from signature to box keys

crypto/src/main/java/net/consensys/cava/crypto/sodium/Box.java

@@ -119,6 +119,33 @@ public static PublicKey fromBytes(byte[] bytes) {
       return Sodium.dup(bytes, PublicKey::new);
     }
 
+    /**
+     * Transforms the Ed25519 signature public key to a Curve25519 public key. See
+     * https://libsodium.gitbook.io/doc/advanced/ed25519-curve25519
+     *
+     * @param publicKey the signature public key
+     * @return the public key as a Curve25519 public key
+     */
+    public static PublicKey forSignaturePublicKey(Signature.PublicKey publicKey) {
+      Pointer publicKeyPtr = null;
+      try {
+        int publicKeyLength = PublicKey.length();
+        publicKeyPtr = Sodium.malloc(publicKeyLength);
+        int rc = Sodium.crypto_sign_ed25519_pk_to_curve25519(publicKeyPtr, publicKey.ptr);
+        if (rc != 0) {
+          throw new SodiumException("crypto_sign_ed25519_pk_to_curve25519: failed with results " + rc);
+        }
+        PublicKey pk = new PublicKey(publicKeyPtr, publicKeyLength);
+        publicKeyPtr = null;
+        return pk;
+      } catch (Throwable e) {
+        if (publicKeyPtr != null) {
+          Sodium.sodium_free(publicKeyPtr);
+        }
+        throw e;
+      }
+    }
+
     /**
      * Obtain the length of the key in bytes (32).
      *
@@ -226,6 +253,34 @@ public static SecretKey fromBytes(byte[] bytes) {
       return Sodium.dup(bytes, SecretKey::new);
     }
 
+    /**
+     * Transforms the Ed25519 secret key to a Curve25519 secret key. See
+     * https://libsodium.gitbook.io/doc/advanced/ed25519-curve25519
+     *
+     * @param secretKey the signature secret key
+     * @return the secret key as a Curve25519 secret key
+     */
+    public static SecretKey forSignatureSecretKey(Signature.SecretKey secretKey) {
+      checkArgument(secretKey.ptr != null, "Signature.SecretKey has been destroyed");
+      Pointer secretKeyPtr = null;
+      try {
+        int secretKeyLength = SecretKey.length();
+        secretKeyPtr = Sodium.malloc(secretKeyLength);
+        int rc = Sodium.crypto_sign_ed25519_sk_to_curve25519(secretKeyPtr, secretKey.ptr);
+        if (rc != 0) {
+          throw new SodiumException("crypto_sign_ed25519_sk_to_curve25519: failed with results " + rc);
+        }
+        SecretKey sk = new SecretKey(secretKeyPtr, secretKeyLength);
+        secretKeyPtr = null;
+        return sk;
+      } catch (Throwable e) {
+        if (secretKeyPtr != null) {
+          Sodium.sodium_free(secretKeyPtr);
+        }
+        throw e;
+      }
+    }
+
     /**
      * Obtain the length of the key in bytes (32).
      *
@@ -485,25 +540,7 @@ public static KeyPair fromSeed(Seed seed) {
      * @return A {@link KeyPair}.
      */
     public static KeyPair forSignatureKeyPair(Signature.KeyPair keyPair) {
-      Pointer signatureSecretKeyPtr = keyPair.secretKey().ptr;
-      checkArgument(signatureSecretKeyPtr != null, "Signature.SecretKey has been destroyed");
-      Pointer secretKey = null;
-      try {
-        int secretKeyLength = SecretKey.length();
-        secretKey = Sodium.malloc(secretKeyLength);
-        int rc = Sodium.crypto_sign_ed25519_sk_to_curve25519(secretKey, keyPair.secretKey().ptr);
-        if (rc != 0) {
-          throw new SodiumException("crypto_sign_ed25519_sk_to_curve25519: failed with results " + rc);
-        }
-        SecretKey sk = new SecretKey(secretKey, secretKeyLength);
-        secretKey = null;
-        return forSecretKey(sk);
-      } catch (Throwable e) {
-        if (secretKey != null) {
-          Sodium.sodium_free(secretKey);
-        }
-        throw e;
-      }
+      return forSecretKey(SecretKey.forSignatureSecretKey(keyPair.secretKey()));
     }
 
     /**

crypto/src/main/java/net/consensys/cava/crypto/sodium/LibSodium.java

@@ -1856,7 +1856,7 @@ int crypto_sign_ed25519_detached(
   int crypto_sign_ed25519_seed_keypair(@Out byte[] pk, @Out byte[] sk, @In byte[] seed);
 
   // int crypto_sign_ed25519_pk_to_curve25519(unsigned char * curve25519_pk, const unsigned char * ed25519_pk);
-  int crypto_sign_ed25519_pk_to_curve25519(@Out byte[] curve25519_pk, @In byte[] ed25519_pk);
+  int crypto_sign_ed25519_pk_to_curve25519(@Out Pointer curve25519_pk, @In Pointer ed25519_pk);
 
   // int crypto_sign_ed25519_sk_to_curve25519(unsigned char * curve25519_sk, const unsigned char * ed25519_sk);
   int crypto_sign_ed25519_sk_to_curve25519(@Out Pointer curve25519_sk, @In Pointer ed25519_sk);

crypto/src/main/java/net/consensys/cava/crypto/sodium/Signature.java

@@ -59,7 +59,7 @@ public final class Signature {
    * A signing public key.
    */
   public static final class PublicKey {
-    private final Pointer ptr;
+    final Pointer ptr;
     private final int length;
 
     private PublicKey(Pointer ptr, int length) {

crypto/src/main/java/net/consensys/cava/crypto/sodium/Sodium.java

@@ -2194,7 +2194,7 @@ static int crypto_sign_ed25519_seed_keypair(byte[] pk, byte[] sk, byte[] seed) {
     return libSodium().crypto_sign_ed25519_seed_keypair(pk, sk, seed);
   }
 
-  static int crypto_sign_ed25519_pk_to_curve25519(byte[] curve25519_pk, byte[] ed25519_pk) {
+  static int crypto_sign_ed25519_pk_to_curve25519(Pointer curve25519_pk, Pointer ed25519_pk) {
     return libSodium().crypto_sign_ed25519_pk_to_curve25519(curve25519_pk, ed25519_pk);
   }
 

crypto/src/test/java/net/consensys/cava/crypto/sodium/BoxTest.java

@@ -14,6 +14,7 @@
 
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assumptions.assumeTrue;
@@ -179,4 +180,15 @@ void checkBoxKeyPairForSignatureKeyPair() {
     Box.KeyPair boxKeyPair = Box.KeyPair.forSignatureKeyPair(signKeyPair);
     assertNotNull(boxKeyPair);
   }
+
+  @Test
+  void checkBoxKeysForSignatureKeys() {
+    Signature.KeyPair keyPair = Signature.KeyPair.random();
+    Box.PublicKey boxPubKey = Box.PublicKey.forSignaturePublicKey(keyPair.publicKey());
+    Box.SecretKey boxSecretKey = Box.SecretKey.forSignatureSecretKey(keyPair.secretKey());
+    assertEquals(boxPubKey, Box.KeyPair.forSecretKey(boxSecretKey).publicKey());
+
+    Box.KeyPair boxKeyPair = Box.KeyPair.forSignatureKeyPair(keyPair);
+    assertEquals(boxKeyPair, Box.KeyPair.forSecretKey(boxSecretKey));
+  }
 }