diff --git a/src/main/java/jota/utils/Signing.java b/src/main/java/jota/utils/Signing.java
index a1e3cdf..19cba57 100644
--- a/src/main/java/jota/utils/Signing.java
+++ b/src/main/java/jota/utils/Signing.java
@@ -54,47 +54,25 @@ public class Signing {
         curl.reset();
         curl.absorb(seed, 0, seed.length);
 
-        final List<Integer> key = new ArrayList<>();
-        int[] buffer = new int[seed.length];
+        final int[] key = new int[length * seed.length * 27];
         int offset = 0;
 
         while (length-- > 0) {
-
             for (int i = 0; i < 27; i++) {
-                curl.squeeze(buffer, offset, buffer.length);
-                for (int j = 0; j < 243; j++) {
-                    key.add(buffer[j]);
-                }
+                curl.squeeze(key, offset, seed.length);
+                offset += seed.length;
             }
         }
-        return to(key);
-    }
-
-    private int[] to(List<Integer> key) {
-        int a[] = new int[key.size()];
-        int i = 0;
-        for (Integer v : key) {
-            a[i++] = v;
-        }
-        return a;
+        return key;
     }
 
     public int[] signatureFragment(int[] normalizedBundleFragment, int[] keyFragment) {
 
-        int[] hash;
-
         for (int i = 0; i < 27; i++) {
-
-            hash = Arrays.copyOfRange(keyFragment, i * 243, (i + 1) * 243);
-
             for (int j = 0; j < 13 - normalizedBundleFragment[i]; j++) {
                 curl.reset()
-                        .absorb(hash, 0, hash.length)
-                        .squeeze(hash, 0, hash.length);
-            }
-
-            for (int j = 0; j < 243; j++) {
-                System.arraycopy(hash, j, keyFragment, i * 243 + j, 1);
+                        .absorb(keyFragment, i * 243, 243)
+                        .squeeze(keyFragment, i * 243, 243);
             }
         }
 
@@ -112,41 +90,34 @@ public class Signing {
     public int[] digests(int[] key) {
 
         int[] digests = new int[(int) Math.floor(key.length / 6561) * 243];
-        int[] buffer = new int[243];
 
         for (int i = 0; i < Math.floor(key.length / 6561); i++) {
             int[] keyFragment = Arrays.copyOfRange(key, i * 6561, (i + 1) * 6561);
 
             for (int j = 0; j < 27; j++) {
-
-                buffer = Arrays.copyOfRange(keyFragment, j * 243, (j + 1) * 243);
                 for (int k = 0; k < 26; k++) {
                     curl.reset()
-                            .absorb(buffer)
-                            .squeeze(buffer);
+                            .absorb(keyFragment, j * 243, 243)
+                            .squeeze(keyFragment, j * 243, 243);
                 }
-                System.arraycopy(buffer, 0, keyFragment, j * 243, 243);
             }
 
             curl.reset();
             curl.absorb(keyFragment, 0, keyFragment.length);
-            curl.squeeze(buffer, 0, buffer.length);
-
-            System.arraycopy(buffer, 0, digests, i * 243, 243);
+            curl.squeeze(digests, i * 243, 243);
         }
         return digests;
     }
 
     public int[] digest(int[] normalizedBundleFragment, int[] signatureFragment) {
         curl.reset();
+        ICurl jCurl = SpongeFactory.create(SpongeFactory.Mode.KERL);
         int[] buffer = new int[243];
 
         for (int i = 0; i < 27; i++) {
             buffer = Arrays.copyOfRange(signatureFragment, i * 243, (i + 1) * 243);
 
             for (int j = normalizedBundleFragment[i] + 13; j-- > 0; ) {
-
-                ICurl jCurl = SpongeFactory.create(SpongeFactory.Mode.KERL);
                 jCurl.reset();
                 jCurl.absorb(buffer);
                 jCurl.squeeze(buffer);
@@ -202,9 +173,7 @@ public class Signing {
 
             int[] digestBuffer = digest(normalizedBundleFragments[i % 3], Converter.trits(signatureFragments[i]));
 
-            for (int j = 0; j < 243; j++) {
-                System.arraycopy(digestBuffer, j, digests, i * 243 + j, 1);
-            }
+            System.arraycopy(digestBuffer, 0, digests, i * 243, 243);
         }
         String address = Converter.trytes(address(digests));
 
diff --git a/src/test/java/jota/SigningTest.java b/src/test/java/jota/SigningTest.java
new file mode 100644
index 0000000..1b4a5a6
--- /dev/null
+++ b/src/test/java/jota/SigningTest.java
@@ -0,0 +1,61 @@
+package jota;
+
+import jota.error.InvalidAddressException;
+import jota.model.Bundle;
+import jota.utils.Checksum;
+import jota.utils.Constants;
+import jota.utils.Converter;
+import jota.utils.InputValidator;
+import jota.utils.IotaAPIUtils;
+import jota.utils.SeedRandomGenerator;
+import jota.utils.Signing;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.util.Arrays;
+
+/**
+ * @author schierlm@gmx.de
+ */
+public class SigningTest {
+
+    private static final String TEST_SEED = "IHDEENZYITYVYSPKAURUZAQKGVJEREFDJMYTANNXXGPZ9GJWTEOJJ9IPMXOGZNQLSNMFDSQOTZAEETUEA";
+    private static final String FIRST_ADDR = "LXQHWNY9CQOHPNMKFJFIJHGEPAENAOVFRDIBF99PPHDTWJDCGHLYETXT9NPUVSNKT9XDTDYNJKJCPQMZCCOZVXMTXC";
+    private static final String SIXTH_ADDR = "HLHRSJNPUUGRYOVYPSTEQJKETXNXDIWQURLTYDBJADGIYZCFXZTTFSOCECPPPPY9BYWPODZOCWJKXEWXDPUYEOTFQA";
+    private static final String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
+    private static final String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
+
+    @Test
+    public void testAddressGeneration() throws InvalidAddressException {
+        assertEquals(FIRST_ADDR, IotaAPIUtils.newAddress(TEST_SEED, 2, 0, true, null));
+        assertEquals(SIXTH_ADDR, IotaAPIUtils.newAddress(TEST_SEED, 2, 5, true, null));
+    }
+
+    @Test
+    public void testSigning() throws InvalidAddressException {
+        // we can sign any hash, so for convenience we will sign the first
+        // address of our test seed
+        // (but remove the checksum) with the key of our fifth address
+        String hashToSign = removeChecksum(FIRST_ADDR);
+        Signing signing = new Signing(null);
+        final int[] key = signing.key(Converter.trits(TEST_SEED), 5, 2);
+        int[] normalizedHash = new Bundle().normalizedBundle(hashToSign);
+        int[] signature = signing.signatureFragment(Arrays.copyOfRange(normalizedHash, 0, 27), Arrays.copyOfRange(key, 0, 6561));
+        assertEquals(SIGNATURE1, Converter.trytes(signature));
+        int[] signature2 = signing.signatureFragment(Arrays.copyOfRange(normalizedHash, 27, 27 * 2), Arrays.copyOfRange(key, 6561, 6561 * 2));
+        assertEquals(SIGNATURE2, Converter.trytes(signature2));
+    }
+
+    @Test
+    public void testVerifying() throws InvalidAddressException {
+        assertTrue(new Signing(null).validateSignatures(removeChecksum(SIXTH_ADDR), new String[] { SIGNATURE1, SIGNATURE2 }, removeChecksum(FIRST_ADDR)));
+    }
+
+    private String removeChecksum(String address) throws InvalidAddressException {
+        assertTrue(Checksum.isValidChecksum(address));
+        return address.substring(0, Constants.ADDRESS_LENGTH_WITHOUT_CHECKSUM);
+    }
+}