diff --git a/hawkbit-security-integration/src/main/java/org/eclipse/hawkbit/security/ControllerPreAuthenticatedSecurityHeaderFilter.java b/hawkbit-security-integration/src/main/java/org/eclipse/hawkbit/security/ControllerPreAuthenticatedSecurityHeaderFilter.java
index 6965afe3f..a536b319d 100644
--- a/hawkbit-security-integration/src/main/java/org/eclipse/hawkbit/security/ControllerPreAuthenticatedSecurityHeaderFilter.java
+++ b/hawkbit-security-integration/src/main/java/org/eclipse/hawkbit/security/ControllerPreAuthenticatedSecurityHeaderFilter.java
@@ -10,7 +10,7 @@ package org.eclipse.hawkbit.security;
 
 import java.util.Arrays;
 import java.util.List;
-import java.util.Set;
+import java.util.stream.Collectors;
 
 import org.eclipse.hawkbit.dmf.json.model.TenantSecurityToken;
 import org.eclipse.hawkbit.repository.TenantConfigurationManagement;
@@ -19,15 +19,11 @@ import org.eclipse.hawkbit.tenancy.configuration.TenantConfigurationKey;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import com.google.common.collect.Sets;
-
 /**
  * An pre-authenticated processing filter which extracts the principal from a
  * request URI and the credential from a request header in a the
  * {@link TenantSecurityToken}.
  *
- *
- *
  */
 public class ControllerPreAuthenticatedSecurityHeaderFilter extends AbstractControllerAuthenticationFilter {
 
@@ -112,12 +108,10 @@ public class ControllerPreAuthenticatedSecurityHeaderFilter extends AbstractCont
             controllerId = secruityToken.getHeader(caCommonNameHeader);
         }
 
-        List<String> knownHashes = splitMultiHash(authorityNameConfigurationValue);
+        List<String> knownHashes = splitMultiHashBySemicolon(authorityNameConfigurationValue);
 
-        Set<HeaderAuthentication> multiHashes = Sets.newHashSetWithExpectedSize(knownHashes.size());
         final String cntlId = controllerId;
-        knownHashes.forEach(hashItem -> multiHashes.add(new HeaderAuthentication(cntlId, hashItem)));
-        return multiHashes;
+        return knownHashes.stream().map(hashItem -> new HeaderAuthentication(cntlId, hashItem)).collect(Collectors.toSet());
     }
 
     /**
@@ -128,8 +122,7 @@ public class ControllerPreAuthenticatedSecurityHeaderFilter extends AbstractCont
      */
     private String getIssuerHashHeader(final TenantSecurityToken secruityToken, final String knownIssuerHashes) {
         // there may be several knownIssuerHashes configured for the tenant
-        // separated by a semicolon
-        List<String> knownHashes = splitMultiHash(knownIssuerHashes);
+        List<String> knownHashes = splitMultiHashBySemicolon(knownIssuerHashes);
 
         // iterate over the headers until we get a null header.
         int iHeader = 1;
@@ -162,7 +155,7 @@ public class ControllerPreAuthenticatedSecurityHeaderFilter extends AbstractCont
         }
     }
 
-    private static List<String> splitMultiHash(String knownIssuerHashes) {
+    private static List<String> splitMultiHashBySemicolon(String knownIssuerHashes) {
         return Arrays.asList(knownIssuerHashes.split(";"));
     }
 }
diff --git a/hawkbit-security-integration/src/main/java/org/eclipse/hawkbit/security/PreAuthTokenSourceTrustAuthenticationProvider.java b/hawkbit-security-integration/src/main/java/org/eclipse/hawkbit/security/PreAuthTokenSourceTrustAuthenticationProvider.java
index 0809f6691..ffe1b7377 100644
--- a/hawkbit-security-integration/src/main/java/org/eclipse/hawkbit/security/PreAuthTokenSourceTrustAuthenticationProvider.java
+++ b/hawkbit-security-integration/src/main/java/org/eclipse/hawkbit/security/PreAuthTokenSourceTrustAuthenticationProvider.java
@@ -123,14 +123,18 @@ public class PreAuthTokenSourceTrustAuthenticationProvider implements Authentica
      * certificate.
      *
      * @param principal
+     *            the {@link HeaderAuthentication} from the header
      * @param credentials
+     *            a single {@link HeaderAuthentication} or a Collection of
+     *            HeaderAuthentication
      * @param tokenDetails
+     *            authentication details
      * @return <code>true</code> if authentication succeeded, otherwise
      *         <code>false</code>
      */
     private boolean calculateAuthenticationSuccess(Object principal, Object credentials, Object tokenDetails) {
         boolean successAuthentication = false;
-        if (Collection.class.isAssignableFrom(credentials.getClass())) {
+        if (credentials instanceof Collection) {
             final Collection<?> multiValueCredentials = (Collection<?>) credentials;
             if (multiValueCredentials.contains(principal)) {
                 successAuthentication = checkSourceIPAddressIfNeccessary(tokenDetails);
diff --git a/hawkbit-security-integration/src/test/java/org/eclipse/hawkbit/security/ControllerPreAuthenticatedSecurityHeaderFilterTest.java b/hawkbit-security-integration/src/test/java/org/eclipse/hawkbit/security/ControllerPreAuthenticatedSecurityHeaderFilterTest.java
index 1275e44b0..15e9c2055 100644
--- a/hawkbit-security-integration/src/test/java/org/eclipse/hawkbit/security/ControllerPreAuthenticatedSecurityHeaderFilterTest.java
+++ b/hawkbit-security-integration/src/test/java/org/eclipse/hawkbit/security/ControllerPreAuthenticatedSecurityHeaderFilterTest.java
@@ -8,8 +8,6 @@
  */
 package org.eclipse.hawkbit.security;
 
-
-//import static org.junit.Assert.*;
 import static org.fest.assertions.api.Assertions.assertThat;
 import static org.junit.Assert.assertEquals;
 import static org.mockito.Matchers.eq;
@@ -105,7 +103,6 @@ public class ControllerPreAuthenticatedSecurityHeaderFilterTest {
                 eq(TenantConfigurationKey.AUTHENTICATION_MODE_HEADER_AUTHORITY_NAME), eq(String.class)))
                         .thenReturn(CONFIG_VALUE_MULTI_HASH);
         assertThat(underTest.getPreAuthenticatedPrincipal(securityToken)).isNull();
-        ;
     }
 
     @Test