diff --git a/src/main/java/entralinked/gui/PidToolDialog.java b/src/main/java/entralinked/gui/PidToolDialog.java
index 039aa60..8724ef6 100644
--- a/src/main/java/entralinked/gui/PidToolDialog.java
+++ b/src/main/java/entralinked/gui/PidToolDialog.java
@@ -15,6 +15,7 @@ import com.formdev.flatlaf.extras.components.FlatTextField;
 
 import entralinked.Entralinked;
 import entralinked.model.user.User;
+import entralinked.utility.MD5;
 import entralinked.utility.SwingUtility;
 
 public class PidToolDialog {
@@ -40,8 +41,8 @@ public class PidToolDialog {
                 return;
             }
             
-            String userId = wfcIdField.getText().replace("-", "");
-            String friendCode = friendCodeField.getText().replace("-", "");
+            String userId = wfcIdField.getText().replace("-", "").replaceAll("\\s+", "");
+            String friendCodeString = friendCodeField.getText().replace("-", "").replaceAll("\\s+", "");
             
             // Make sure WFC ID is valid
             if(!WFC_ID_PATTERN.matcher(userId).matches()) {
@@ -50,13 +51,12 @@ public class PidToolDialog {
             }
             
             // Make sure Friend Code is valid
-            if(!FRIEND_CODE_PATTERN.matcher(friendCode).matches()) {
+            if(!FRIEND_CODE_PATTERN.matcher(friendCodeString).matches()) {
                 JOptionPane.showMessageDialog(dialog, "Please enter a valid Friend Code.", "Attention", JOptionPane.WARNING_MESSAGE);
                 return;
             }
             
             User user = entralinked.getUserManager().getUser(userId.substring(0, 13));
-            int profileId = (int)(Long.parseLong(friendCode) & 0x7FFFFFFF);
             
             // Make sure user exists
             if(user == null) {
@@ -64,6 +64,26 @@ public class PidToolDialog {
                 return;
             }
             
+            long friendCode = Long.parseLong(friendCodeString);
+            int profileId = (int)(friendCode & 0x7FFFFFFF);
+            int checksum = (int)(friendCode >> 32);
+            
+            // Compute friend code checksum
+            byte[] buffer = {0x00, 0x00, 0x00, 0x00, 0x4A, 0x41, 0x52, 0x49}; // Last 4 bytes is inverted game code (IRAJ)
+            buffer[0] = (byte)(profileId & 0xFF);
+            buffer[1] = (byte)(profileId >> 8 & 0xFF);
+            buffer[2] = (byte)(profileId >> 16 & 0xFF);
+            buffer[3] = (byte)(profileId >> 24 & 0xFF);
+            byte[] hash = MD5.digest(buffer);
+            int computedChecksum = hash[0] >> 1 & 0x7F;
+            
+            // Compare checksums
+            if(computedChecksum != checksum) {
+                JOptionPane.showMessageDialog(dialog, "This is not a valid Friend Code. Please check for typos.", "Attention", JOptionPane.WARNING_MESSAGE);
+                return;
+            }
+            
+            // Everything checks out -- update the profile id!
             user.setProfileIdOverride(profileId);
             JOptionPane.showMessageDialog(dialog,
                     "All done! Please restart your game and use Game Sync.\nGame profile data will be updated and saved once you do so.");
diff --git a/src/main/java/entralinked/utility/MD5.java b/src/main/java/entralinked/utility/MD5.java
index 845a02c..7cb2e0c 100644
--- a/src/main/java/entralinked/utility/MD5.java
+++ b/src/main/java/entralinked/utility/MD5.java
@@ -21,6 +21,13 @@ public class MD5 {
      * @return A hex-formatted MD5 hash of the specified input.
      */
     public static String digest(String string) {
+        return StringUtil.toHexStringPadded(digest(string.getBytes(StandardCharsets.ISO_8859_1)));
+    }
+    
+    /**
+     * @return An MD5 hash of the specified input.
+     */
+    public static byte[] digest(byte[] bytes) {
         if(digest == null) {
             try {
                 digest = MessageDigest.getInstance("MD5");
@@ -29,6 +36,6 @@ public class MD5 {
             }
         }
         
-        return StringUtil.toHexStringPadded(digest.digest(string.getBytes(StandardCharsets.ISO_8859_1)));
+        return digest.digest(bytes);
     }
 }