Add public key to address transformation (#154)

eth/src/main/java/org/apache/tuweni/eth/Address.java

@@ -17,12 +17,36 @@
 
 import org.apache.tuweni.bytes.Bytes;
 import org.apache.tuweni.bytes.DelegatingBytes;
+import org.apache.tuweni.crypto.SECP256K1;
 
 /**
  * An Ethereum account address.
  */
 public final class Address extends DelegatingBytes {
 
+  /**
+   * Transform a public key into an Ethereum address.
+   * 
+   * @param publicKey the public key
+   * @return the address
+   */
+  public static Address fromPublicKey(SECP256K1.PublicKey publicKey) {
+    requireNonNull(publicKey);
+    return fromPublicKeyBytes(publicKey.bytes());
+  }
+
+  /**
+   * Transform a public key into an Ethereum address.
+   * 
+   * @param bytes the bytes of the public key
+   * @return the address
+   */
+  public static Address fromPublicKeyBytes(Bytes bytes) {
+    requireNonNull(bytes);
+    Bytes value = org.apache.tuweni.crypto.Hash.keccak256(bytes);
+    return new Address(value.slice(12));
+  }
+
   /**
    * Create an address from Bytes.
    *

eth/src/test/java/org/apache/tuweni/eth/PublicKeyToAddressTest.java

@@ -0,0 +1,35 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE
+ * file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file
+ * to You under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the
+ * License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ */
+package org.apache.tuweni.eth;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.apache.tuweni.bytes.Bytes32;
+import org.apache.tuweni.crypto.SECP256K1;
+import org.apache.tuweni.junit.BouncyCastleExtension;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+@ExtendWith(BouncyCastleExtension.class)
+class PublicKeyToAddressTest {
+
+  @Test
+  public void testTransformFromSecretKeyToAddress() {
+    SECP256K1.SecretKey key = SECP256K1.SecretKey
+        .fromBytes(Bytes32.fromHexString("4ee50b74f1f903a80df52c4f6b43a17bc1319636e203f3fe9c09294f74907849"));
+    SECP256K1.PublicKey pk = SECP256K1.KeyPair.fromSecretKey(key).publicKey();
+    Address addr = Address.fromPublicKeyBytes(pk.bytes());
+    assertEquals(Address.fromHexString("0x25851ab5f8151a68d0014fd508609bbf6b4d6d1d"), addr);
+  }
+}