diff --git a/src/main/scala/com/fluency03/blockchain/core/Wallet.scala b/src/main/scala/com/fluency03/blockchain/core/Wallet.scala
index fcaf404..65173a8 100644
--- a/src/main/scala/com/fluency03/blockchain/core/Wallet.scala
+++ b/src/main/scala/com/fluency03/blockchain/core/Wallet.scala
@@ -4,6 +4,7 @@ package core
 import java.security.KeyPair
 
 import com.fluency03.blockchain.core.Wallet.balanceOfWallet
+import com.fluency03.blockchain.core.Transaction.signTxIn
 
 import scala.collection.mutable
 
@@ -15,6 +16,9 @@ case class Wallet() {
 
   def balance(uTxOs: mutable.Map[Outpoint, TxOut]): Long = balanceOfWallet(this, uTxOs)
 
+  def sign(txId: String, txIn: TxIn, uTxOs: mutable.Map[Outpoint, TxOut]): Option[TxIn] =
+    signTxIn(txId, txIn, keyPair, uTxOs)
+
 }
 
 object Wallet {
diff --git a/src/test/scala/com/fluency03/blockchain/core/WalletTest.scala b/src/test/scala/com/fluency03/blockchain/core/WalletTest.scala
index 856fe73..ba25c80 100644
--- a/src/test/scala/com/fluency03/blockchain/core/WalletTest.scala
+++ b/src/test/scala/com/fluency03/blockchain/core/WalletTest.scala
@@ -1,4 +1,5 @@
-package com.fluency03.blockchain.core
+package com.fluency03.blockchain
+package core
 
 import com.fluency03.blockchain.core.Wallet._
 
@@ -22,5 +23,21 @@ class WalletTest extends FlatSpec with Matchers {
     wallet.balance(uTxOs) shouldEqual 40
   }
 
+  "Wallet" should "be able to sign a TxIn." in {
+    val wallet = Wallet()
+    val id = "".toSha256
+    val txIn = TxIn(Outpoint("def0", 0), "abc")
+    val uTxOs: mutable.Map[Outpoint, TxOut] = mutable.Map.empty[Outpoint, TxOut]
+
+    val signedTxIn0 = wallet.sign(id, txIn, uTxOs)
+    signedTxIn0 shouldEqual None
+
+    uTxOs += (Outpoint("def0", 0) -> TxOut(wallet.address, 40))
+    uTxOs += (Outpoint("def0", 1) -> TxOut("abc4", 40))
+
+    val signedTxIn = wallet.sign(id, txIn, uTxOs)
+    signedTxIn shouldEqual Some(TxIn(Outpoint("def0", 0), signedTxIn.get.signature))
+  }
+
 
 }