diff --git a/src/main/scala/com/fluency03/blockchain/api/actors/PeerActor.scala b/src/main/scala/com/fluency03/blockchain/api/actors/PeerActor.scala
index ac238b5..bcde51b 100644
--- a/src/main/scala/com/fluency03/blockchain/api/actors/PeerActor.scala
+++ b/src/main/scala/com/fluency03/blockchain/api/actors/PeerActor.scala
@@ -5,36 +5,38 @@ import java.security.KeyPair
 
 import akka.actor.Props
 import com.fluency03.blockchain.api.actors.PeerActor._
-import com.fluency03.blockchain.core.Peer
+import com.fluency03.blockchain.core.{Peer, Wallet}
 
 import scala.collection.mutable
 
 object PeerActor {
   final case object GetPublicKeys
-  final case object CreateKeyPair
+  final case object CreateWallet
   def props: Props = Props[PeerActor]
 }
 
 class PeerActor extends ActorSupport {
-  override def preStart(): Unit = log.info("{} started!", this.getClass.getSimpleName)
+  override def preStart(): Unit = {
+    log.info("{} started!", this.getClass.getSimpleName)
+    addWallet()
+    log.info("Created initial wallet: {}", wallets.head._1)
+  }
   override def postStop(): Unit = log.info("{} stopped!", this.getClass.getSimpleName)
 
   // TODO (Chang): need persistence
-  val wallets = mutable.Map.empty[String, KeyPair]
-  addNewKeyPair()
-
+  val wallets = mutable.Map.empty[String, Wallet]
   val others = mutable.Map.empty[String, Peer]
 
   def receive: Receive = {
-    case GetPublicKeys => sender() ! wallets.values.map(_.getPublic.toHex).toSet
-    case CreateKeyPair => sender() ! addNewKeyPair().getPublic.toHex
+    case GetPublicKeys => sender() ! wallets.values.map(_.address).toSet
+    case CreateWallet => sender() ! addWallet()
     case _ => unhandled _
   }
 
-  private def addNewKeyPair(): KeyPair = {
-    val pair: KeyPair = Crypto.generateKeyPair()
-    wallets += (pair.getPublic.toHex -> pair)
-    pair
+  private def addWallet(): String = {
+    val newWallet = Wallet()
+    wallets += (newWallet.address -> newWallet)
+    newWallet.address
   }
 
 }
diff --git a/src/main/scala/com/fluency03/blockchain/core/Wallet.scala b/src/main/scala/com/fluency03/blockchain/core/Wallet.scala
new file mode 100644
index 0000000..fcaf404
--- /dev/null
+++ b/src/main/scala/com/fluency03/blockchain/core/Wallet.scala
@@ -0,0 +1,28 @@
+package com.fluency03.blockchain
+package core
+
+import java.security.KeyPair
+
+import com.fluency03.blockchain.core.Wallet.balanceOfWallet
+
+import scala.collection.mutable
+
+case class Wallet() {
+
+  private[this] val keyPair: KeyPair = Crypto.generateKeyPair()
+
+  lazy val address: String = keyPair.getPublic.toHex
+
+  def balance(uTxOs: mutable.Map[Outpoint, TxOut]): Long = balanceOfWallet(this, uTxOs)
+
+}
+
+object Wallet {
+
+  def balanceOfWallet(wallet: Wallet, uTxOs: mutable.Map[Outpoint, TxOut]): Long =
+    balanceOfAddress(wallet.address, uTxOs)
+
+  def balanceOfAddress(address: String, uTxOs: mutable.Map[Outpoint, TxOut]): Long =
+    uTxOs.values.filter(_.address == address).map(_.amount).sum
+
+}
\ No newline at end of file
diff --git a/src/test/scala/com/fluency03/blockchain/api/actors/PeerActorTest.scala b/src/test/scala/com/fluency03/blockchain/api/actors/PeerActorTest.scala
index e176005..cf8706c 100644
--- a/src/test/scala/com/fluency03/blockchain/api/actors/PeerActorTest.scala
+++ b/src/test/scala/com/fluency03/blockchain/api/actors/PeerActorTest.scala
@@ -2,7 +2,7 @@ package com.fluency03.blockchain.api.actors
 
 import akka.actor.{ActorRef, ActorSystem, Props}
 import akka.testkit.{ImplicitSender, TestKit}
-import com.fluency03.blockchain.api.actors.PeerActor.GetPublicKeys
+import com.fluency03.blockchain.api.actors.PeerActor.{CreateWallet, GetPublicKeys}
 import org.scalatest.{BeforeAndAfterAll, Matchers, WordSpecLike}
 
 class PeerActorTest extends TestKit(ActorSystem("PeerActorTest")) with ImplicitSender
@@ -22,6 +22,13 @@ class PeerActorTest extends TestKit(ActorSystem("PeerActorTest")) with ImplicitS
       val publicKeys = expectMsgType[Set[String]]
       publicKeys.size shouldEqual 1
 
+      peerActor ! CreateWallet
+      expectMsgType[String]
+
+      peerActor ! GetPublicKeys
+      val publicKeys2 = expectMsgType[Set[String]]
+      publicKeys2.size shouldEqual 2
+
       peerActor ! "other"
       expectNoMessage
     }
diff --git a/src/test/scala/com/fluency03/blockchain/core/WalletTest.scala b/src/test/scala/com/fluency03/blockchain/core/WalletTest.scala
new file mode 100644
index 0000000..856fe73
--- /dev/null
+++ b/src/test/scala/com/fluency03/blockchain/core/WalletTest.scala
@@ -0,0 +1,26 @@
+package com.fluency03.blockchain.core
+
+import com.fluency03.blockchain.core.Wallet._
+
+import org.scalatest.{FlatSpec, Matchers}
+
+import scala.collection.mutable
+
+class WalletTest extends FlatSpec with Matchers {
+
+  "balanceOfWallet" should "obtain the balance of a Wallet based on UTXOs." in {
+    val wallet = Wallet()
+    val uTxOs: mutable.Map[Outpoint, TxOut] = mutable.Map.empty[Outpoint, TxOut]
+
+    balanceOfWallet(wallet, uTxOs) shouldEqual 0
+    wallet.balance(uTxOs) shouldEqual 0
+
+    uTxOs += (Outpoint("def0", 0) -> TxOut(wallet.address, 40))
+    uTxOs += (Outpoint("def0", 1) -> TxOut("abc4", 40))
+
+    balanceOfWallet(wallet, uTxOs) shouldEqual 40
+    wallet.balance(uTxOs) shouldEqual 40
+  }
+
+
+}