diff --git a/enabler/src/de/schildbach/pte/AbstractHafasMobileProvider.java b/enabler/src/de/schildbach/pte/AbstractHafasMobileProvider.java
index 06cb82ba..7c18b3bc 100644
--- a/enabler/src/de/schildbach/pte/AbstractHafasMobileProvider.java
+++ b/enabler/src/de/schildbach/pte/AbstractHafasMobileProvider.java
@@ -43,7 +43,11 @@ import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;
 
+import com.google.common.base.Charsets;
 import com.google.common.base.Joiner;
+import com.google.common.hash.HashCode;
+import com.google.common.hash.HashFunction;
+import com.google.common.hash.Hashing;
 
 import de.schildbach.pte.dto.Departure;
 import de.schildbach.pte.dto.Fare;
@@ -78,6 +82,10 @@ public abstract class AbstractHafasMobileProvider extends AbstractHafasProvider
     public String apiAuthorization;
     @Nullable
     public String apiClient;
+    @Nullable
+    public String requestChecksumSalt;
+
+    private static final HashFunction MD5 = Hashing.md5();
 
     public AbstractHafasMobileProvider(final NetworkId network, final HttpUrl apiBase, final Product[] productsMap) {
         super(network, productsMap);
@@ -100,6 +108,11 @@ public abstract class AbstractHafasMobileProvider extends AbstractHafasProvider
         return this;
     }
 
+    protected AbstractHafasMobileProvider setRequestChecksumSalt(final String requestChecksumSalt) {
+        this.requestChecksumSalt = requestChecksumSalt;
+        return this;
+    }
+
     @Override
     public NearbyLocationsResult queryNearbyLocations(final EnumSet<LocationType> types, final Location location,
             final int maxDistance, final int maxLocations) throws IOException {
@@ -144,7 +157,7 @@ public abstract class AbstractHafasMobileProvider extends AbstractHafasProvider
                         + "\"getPOIs\":" + getPOIs + "}", //
                 false);
 
-        final HttpUrl url = checkNotNull(mgateEndpoint);
+        final HttpUrl url = requestUrl(request);
         final CharSequence page = httpClient.get(url, request, "application/json");
 
         try {
@@ -209,7 +222,7 @@ public abstract class AbstractHafasMobileProvider extends AbstractHafasProvider
                         + getPasslist + "}",
                 false);
 
-        final HttpUrl url = checkNotNull(mgateEndpoint);
+        final HttpUrl url = requestUrl(request);
         final CharSequence page = httpClient.get(url, request, "application/json");
 
         try {
@@ -317,7 +330,7 @@ public abstract class AbstractHafasMobileProvider extends AbstractHafasProvider
                         + ",\"meta\":false},\"maxLoc\":" + DEFAULT_MAX_LOCATIONS + "}}",
                 false);
 
-        final HttpUrl url = checkNotNull(mgateEndpoint);
+        final HttpUrl url = requestUrl(request);
         final CharSequence page = httpClient.get(url, request, "application/json");
 
         try {
@@ -414,7 +427,7 @@ public abstract class AbstractHafasMobileProvider extends AbstractHafasProvider
                 + "\"getPolyline\":false,\"getPasslist\":true,\"getIST\":false,\"getEco\":false,\"extChgTime\":-1}", //
                 false);
 
-        final HttpUrl url = checkNotNull(mgateEndpoint);
+        final HttpUrl url = requestUrl(request);
         final CharSequence page = httpClient.get(url, request, "application/json");
 
         try {
@@ -597,6 +610,16 @@ public abstract class AbstractHafasMobileProvider extends AbstractHafasProvider
                 + "\"formatted\":" + formatted + "}";
     }
 
+    private HttpUrl requestUrl(final String body) {
+        final HttpUrl.Builder url = checkNotNull(mgateEndpoint).newBuilder();
+        if (requestChecksumSalt != null) {
+            final HashCode checksum = MD5.newHasher().putString(body, Charsets.UTF_8)
+                    .putString(requestChecksumSalt, Charsets.UTF_8).hash();
+            url.addQueryParameter("checksum", checksum.toString());
+        }
+        return url.build();
+    }
+
     private String jsonLocation(final Location location) {
         if (location.type == LocationType.STATION && location.hasId())
             return "{\"type\":\"S\",\"extId\":" + JSONObject.quote(location.id) + "}";