diff --git a/src/main/java/hs/fulda/de/ci/exam/project/Account.java b/src/main/java/hs/fulda/de/ci/exam/project/Account.java
index b5bbaa8..7097e7e 100644
--- a/src/main/java/hs/fulda/de/ci/exam/project/Account.java
+++ b/src/main/java/hs/fulda/de/ci/exam/project/Account.java
@@ -33,6 +33,15 @@ public class Account {
         this.status = status;
     }
 
+    public boolean isEnabled() {
+        if(status == AccountStatus.ACTIVE) return true;
+        return false;
+    }
+
+    public String getPasswordHash() {
+        return new PasswordEncoder().encode(password);
+    }
+
     public enum AccountStatus {
         ACTIVE,
         CLOSED,
@@ -67,4 +76,17 @@ public class Account {
     }
 
 }
+class PasswordEncoder{
+    String encode(String password){
+        int p = 31;
+        int m = (int) Math.pow(10, 9) + 9;
+        int hash_value = 0;
+        int p_pow = 1;
+        for (char c : password.toCharArray()) {
+            hash_value = (hash_value + (c - 'a' + 1) * p_pow) % m;
+            p_pow = (p_pow * p) % m;
+        }
+    return Integer.toString(hash_value);
+    }
+}
 
diff --git a/src/main/java/hs/fulda/de/ci/exam/project/AccountRepository.java b/src/main/java/hs/fulda/de/ci/exam/project/AccountRepository.java
index db9d3e8..90a96db 100644
--- a/src/main/java/hs/fulda/de/ci/exam/project/AccountRepository.java
+++ b/src/main/java/hs/fulda/de/ci/exam/project/AccountRepository.java
@@ -14,6 +14,11 @@ public class AccountRepository {
         }
         return false;
     }
+    Account findById(String id){
+        Account account = accountList.get(id);
+        return account;
+    }
+
     private String generateKey(Account account) {
         return String.format("%s", account.getId());
     }
diff --git a/src/main/java/hs/fulda/de/ci/exam/project/AccountService.java b/src/main/java/hs/fulda/de/ci/exam/project/AccountService.java
new file mode 100644
index 0000000..789ecba
--- /dev/null
+++ b/src/main/java/hs/fulda/de/ci/exam/project/AccountService.java
@@ -0,0 +1,24 @@
+package hs.fulda.de.ci.exam.project;
+
+public class AccountService {
+    private final AccountRepository accountRepository;
+    private final PasswordEncoder passwordEncoder;
+
+    public AccountService(AccountRepository accountRepository, PasswordEncoder passwordEncoder) {
+        this.accountRepository = accountRepository;
+        this.passwordEncoder = passwordEncoder;
+    }
+    public boolean isValidAccount(String id, String password){
+        Account account = accountRepository.findById(id);
+        return isEnabledAccount(account) && isValidPassword(account, password);
+    }
+
+    private boolean isEnabledAccount(Account account) {
+        return account!= null && account.isEnabled();
+    }
+
+    private boolean isValidPassword(Account account, String password) {
+        String encodedPassword = passwordEncoder.encode(password);
+        return encodedPassword.equals(account.getPasswordHash());
+    }
+}
diff --git a/src/test/java/hs/fulda/de/ci/exam/project/AccountServiceTest.java b/src/test/java/hs/fulda/de/ci/exam/project/AccountServiceTest.java
new file mode 100644
index 0000000..c9f1bdc
--- /dev/null
+++ b/src/test/java/hs/fulda/de/ci/exam/project/AccountServiceTest.java
@@ -0,0 +1,35 @@
+package hs.fulda.de.ci.exam.project;
+
+import org.junit.Before;
+
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class AccountServiceTest {
+    private static final String PASSWORD = "password";
+
+    private static final Account ENABLED_USER =
+            new Account("user id", "hash", Account.AccountStatus.ACTIVE);
+
+    private static final Account DISABLED_USER =
+            new Account("disabled user id", "disabled user password hash", Account.AccountStatus.CLOSED);
+
+    private AccountRepository accountRepository;
+    private PasswordEncoder passwordEncoder;
+    private AccountService accountService;
+
+    @Before
+    public void setup() {
+        passwordEncoder = createPasswordEncoder();
+        accountService = new AccountService(accountRepository, passwordEncoder);
+    }
+
+    private PasswordEncoder createPasswordEncoder() {
+        PasswordEncoder mock = mock(PasswordEncoder.class);
+        when(mock.encode(anyString())).thenReturn("any password hash");
+        when(mock.encode(PASSWORD)).thenReturn(ENABLED_USER.getPasswordHash());
+        return mock;
+    }
+
+}