diff --git a/enzevalos_iphone.xcodeproj/project.pbxproj b/enzevalos_iphone.xcodeproj/project.pbxproj
index fe470109f72945b05264a001dde4a28520905518..b0c4aa04d02c8135164c23818fe412d27445b415 100644
--- a/enzevalos_iphone.xcodeproj/project.pbxproj
+++ b/enzevalos_iphone.xcodeproj/project.pbxproj
@@ -154,6 +154,10 @@
 		47691A8C1ECC3EC7004BCFC5 /* EphemeralMail.swift in Sources */ = {isa = PBXBuildFile; fileRef = 47691A8B1ECC3EC7004BCFC5 /* EphemeralMail.swift */; };
 		477548DE21F5DABE000B22A8 /* MailServerConnectionError.swift in Sources */ = {isa = PBXBuildFile; fileRef = 477548DD21F5DABE000B22A8 /* MailServerConnectionError.swift */; };
 		477548DF21F5DABE000B22A8 /* MailServerConnectionError.swift in Sources */ = {isa = PBXBuildFile; fileRef = 477548DD21F5DABE000B22A8 /* MailServerConnectionError.swift */; };
+		477548E221F77466000B22A8 /* SecurityIndicator.swift in Sources */ = {isa = PBXBuildFile; fileRef = 477548E121F77466000B22A8 /* SecurityIndicator.swift */; };
+		477548E421F77BA0000B22A8 /* StudyParameterProtocol.swift in Sources */ = {isa = PBXBuildFile; fileRef = 477548E321F77BA0000B22A8 /* StudyParameterProtocol.swift */; };
+		477548E521F77DF5000B22A8 /* StudyParameterProtocol.swift in Sources */ = {isa = PBXBuildFile; fileRef = 477548E321F77BA0000B22A8 /* StudyParameterProtocol.swift */; };
+		477548E621F77DF7000B22A8 /* SecurityIndicator.swift in Sources */ = {isa = PBXBuildFile; fileRef = 477548E121F77466000B22A8 /* SecurityIndicator.swift */; };
 		47953AA91FD7000200D4631A /* bitcoinde.asc in Resources */ = {isa = PBXBuildFile; fileRef = 47953AA81FD7000200D4631A /* bitcoinde.asc */; };
 		47953AAA1FD7000200D4631A /* bitcoinde.asc in Resources */ = {isa = PBXBuildFile; fileRef = 47953AA81FD7000200D4631A /* bitcoinde.asc */; };
 		479B5977206914BE00B3944D /* CryptoTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 479B5976206914BE00B3944D /* CryptoTests.swift */; };
@@ -351,6 +355,8 @@
 		47691A891ECB56D1004BCFC5 /* Mail.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Mail.swift; sourceTree = "<group>"; };
 		47691A8B1ECC3EC7004BCFC5 /* EphemeralMail.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = EphemeralMail.swift; sourceTree = "<group>"; };
 		477548DD21F5DABE000B22A8 /* MailServerConnectionError.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MailServerConnectionError.swift; sourceTree = "<group>"; };
+		477548E121F77466000B22A8 /* SecurityIndicator.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SecurityIndicator.swift; sourceTree = "<group>"; };
+		477548E321F77BA0000B22A8 /* StudyParameterProtocol.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = StudyParameterProtocol.swift; sourceTree = "<group>"; };
 		47953AA81FD7000200D4631A /* bitcoinde.asc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = bitcoinde.asc; sourceTree = "<group>"; };
 		479B5976206914BE00B3944D /* CryptoTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CryptoTests.swift; sourceTree = "<group>"; };
 		479C649521F2139B00A01071 /* support_pk.asc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = support_pk.asc; sourceTree = "<group>"; };
@@ -625,6 +631,15 @@
 			name = mail;
 			sourceTree = "<group>";
 		};
+		477548E021F77445000B22A8 /* study parameters */ = {
+			isa = PBXGroup;
+			children = (
+				477548E121F77466000B22A8 /* SecurityIndicator.swift */,
+				477548E321F77BA0000B22A8 /* StudyParameterProtocol.swift */,
+			);
+			path = "study parameters";
+			sourceTree = "<group>";
+		};
 		47B91AC01EC0C1CF000AE3EE /* coredata */ = {
 			isa = PBXGroup;
 			children = (
@@ -845,6 +860,7 @@
 		A17FDFF1202C680A00F7BA89 /* debug and study */ = {
 			isa = PBXGroup;
 			children = (
+				477548E021F77445000B22A8 /* study parameters */,
 				A17FDFF2202C685800F7BA89 /* StudySettings.swift */,
 				47D1302A1F7CEE6D007B14DF /* DebugSettings.swift */,
 				A111F6AB1FA77AF80060AFDE /* Logging */,
@@ -1433,6 +1449,7 @@
 				3E9709031FAC95F5005825C9 /* MessageBodyTableViewCell.swift in Sources */,
 				3E9709041FAC95F5005825C9 /* ReadVENDelegate.swift in Sources */,
 				3E9709061FAC95F5005825C9 /* PersistentKey+CoreDataClass.swift in Sources */,
+				477548E621F77DF7000B22A8 /* SecurityIndicator.swift in Sources */,
 				3E9709081FAC95F5005825C9 /* KeyViewController.swift in Sources */,
 				3E9709091FAC95F5005825C9 /* ExportCells.swift in Sources */,
 				3E97090B1FAC95F5005825C9 /* CNMailAddressesExtension.swift in Sources */,
@@ -1456,6 +1473,7 @@
 				3E9709231FAC95F5005825C9 /* MailAddress.swift in Sources */,
 				3E9709241FAC95F5005825C9 /* MailHandlerDelegator.swift in Sources */,
 				3E97092A1FAC95F5005825C9 /* LabelStyleKit.swift in Sources */,
+				477548E521F77DF5000B22A8 /* StudyParameterProtocol.swift in Sources */,
 				3E97092C1FAC95F5005825C9 /* SubBadgeTableViewCell.swift in Sources */,
 				3E97092D1FAC95F5005825C9 /* FrequentCell.swift in Sources */,
 				3E97092E1FAC95F5005825C9 /* ListViewController.swift in Sources */,
@@ -1504,6 +1522,7 @@
 				8428A86F1F436A1E007649A5 /* InviteFriendViewController.swift in Sources */,
 				A1735DFA205AB88500B336DB /* SendViewState.swift in Sources */,
 				475B00331F7B9565006CDD41 /* SwiftPGP.swift in Sources */,
+				477548E421F77BA0000B22A8 /* StudyParameterProtocol.swift in Sources */,
 				3EB4FAA420120096001D0625 /* DialogOption.swift in Sources */,
 				F14239C11F30A99C00998A83 /* QRCodeGenerator.swift in Sources */,
 				F1AF938F1E2D04BA00755128 /* CustomCells.swift in Sources */,
@@ -1526,6 +1545,7 @@
 				F12060801DA540FE00F6EF37 /* RefreshControlExtension.swift in Sources */,
 				A13526811D955BDF00D3BFE1 /* enzevalos_iphone.xcdatamodeld in Sources */,
 				472F39821E1E5347009260FB /* Mail_Address+CoreDataProperties.swift in Sources */,
+				477548E221F77466000B22A8 /* SecurityIndicator.swift in Sources */,
 				476373C21E09BA88004D5EFE /* UserData.swift in Sources */,
 				A1EB05A01D95696C008659C1 /* MessageBodyTableViewCell.swift in Sources */,
 				F18B44621E73286C0080C041 /* ReadVENDelegate.swift in Sources */,
diff --git a/enzevalos_iphone/HideShowPasswordTextField.swift b/enzevalos_iphone/HideShowPasswordTextField.swift
index 451696a891fb914fdfec85d91d8efabcc37682c9..3864480b04bd5c4704483a08a269aedbb4bf2740 100644
--- a/enzevalos_iphone/HideShowPasswordTextField.swift
+++ b/enzevalos_iphone/HideShowPasswordTextField.swift
@@ -3,7 +3,7 @@
 //  Guidebook
 //
 //  Created by Mike Sprague on 4/15/16.
-// See: https://github.com/Guidebook/HideShowPasswordTextField
+//  See: https://github.com/Guidebook/HideShowPasswordTextField
 //
 //
 
diff --git a/enzevalos_iphone/LabelStyleKit.swift b/enzevalos_iphone/LabelStyleKit.swift
index f1757a4485a3af9ac52147ba9d69d411813aaca9..88787b5489d573fa2bb788a4112ca908429bd812 100644
--- a/enzevalos_iphone/LabelStyleKit.swift
+++ b/enzevalos_iphone/LabelStyleKit.swift
@@ -8,7 +8,6 @@
 //  Generated by PaintCode
 //  http://www.paintcodeapp.com
 //
-//  This code was partly generated by Trial version of PaintCode, therefore cannot be used for commercial purposes.
 //
 
 
diff --git a/enzevalos_iphone/MailServerConnectionError.swift b/enzevalos_iphone/MailServerConnectionError.swift
index 483f90112f810a87267b113ac91aadf97cf10cef..b8856c36f4aa836c8b224ce5503f1e8a10f80a64 100644
--- a/enzevalos_iphone/MailServerConnectionError.swift
+++ b/enzevalos_iphone/MailServerConnectionError.swift
@@ -104,7 +104,7 @@ enum MailServerConnectionError: Error {
         case "The server does not support STARTTLS connections.".uppercased():
             mscError = .StartTLSNotAvailableError
             break
-        case  "The SMTP storage limit was hit while trying to send a large message.".uppercased():
+        case "The SMTP storage limit was hit while trying to send a large message.".uppercased():
             mscError = .StorageLimitSMTPError
             break
         case "Authentication is required for this SMTP server.".uppercased():
diff --git a/enzevalos_iphone/PasswordToggleVisibilityView.swift b/enzevalos_iphone/PasswordToggleVisibilityView.swift
index c39d6c2b8615d7f0d65a8c4316d0980e5609dc83..65eb319a7a441ff5164137696586425aa9ddbaf9 100644
--- a/enzevalos_iphone/PasswordToggleVisibilityView.swift
+++ b/enzevalos_iphone/PasswordToggleVisibilityView.swift
@@ -3,7 +3,7 @@
 //  Guidebook
 //
 //  Created by Mike Sprague on 4/14/16.
-// See: https://github.com/Guidebook/HideShowPasswordTextField
+//  See: https://github.com/Guidebook/HideShowPasswordTextField
 //
 //
 
diff --git a/enzevalos_iphone/StudySettings.swift b/enzevalos_iphone/StudySettings.swift
index c4e71fcc74f622a458fd493422c586d9f368cd8c..ec9c8e22b98bb2e65edf85cfbfdf453590f3928f 100644
--- a/enzevalos_iphone/StudySettings.swift
+++ b/enzevalos_iphone/StudySettings.swift
@@ -24,6 +24,7 @@ import KeychainAccess
 enum StudyParamter: Int {
     case Warning = 0
     case Invitation = 1
+    case Indicator = 2
 
     var name: String {
         get {
@@ -32,6 +33,8 @@ enum StudyParamter: Int {
                 return "warning"
             case .Invitation:
                 return "invitation"
+            case .Indicator:
+                return "indicator"
             }
         }
     }
@@ -43,7 +46,10 @@ enum StudyParamter: Int {
                 return "hideWarnings"
             case .Invitation:
                 return "invitation mode"
+            case .Indicator:
+                return "indicator mode"
             }
+            
         }
     }
     var numberOfTreatments: UInt32 {
@@ -53,6 +59,8 @@ enum StudyParamter: Int {
                 return 2
             case .Invitation:
                 return 3
+            case .Indicator:
+                return 2
             }
         }
     }
@@ -65,10 +73,13 @@ enum InvitationMode: Int {
     case FreeText
 }
 
+
+
+
 class StudySettings {
     static var studyMode = true
     static var presentFirstQuestionaireMail = false
-    static let parameters = [StudyParamter.Invitation]
+    static let parameters = [StudyParamter.Indicator]
     
     static let bitcoinStudyBody =
     """
@@ -153,7 +164,6 @@ class StudySettings {
 
     static var invitationsmode: InvitationMode {
         get {
-            return UserManager.loadInvitationMode()
             let value = UserDefaults.standard.integer(forKey: StudyParamter.Invitation.keyName)
             if let mode = InvitationMode.init(rawValue: value) {
                 return mode
diff --git a/enzevalos_iphone/study parameters/SecurityIndicator.swift b/enzevalos_iphone/study parameters/SecurityIndicator.swift
new file mode 100644
index 0000000000000000000000000000000000000000..12d36e151a9d39bb7d61e4420320855bf0445626
--- /dev/null
+++ b/enzevalos_iphone/study parameters/SecurityIndicator.swift	
@@ -0,0 +1,138 @@
+//
+//  SecurityIndicator.swift
+//  enzevalos_iphone
+//
+//  Created by Oliver Wiese on 22.01.19.
+//  Copyright © 2019 fu-berlin. All rights reserved.
+//
+
+import Foundation
+
+
+
+enum SecurityIndicator: Int, StudyParameterProtocol {
+    case letter = 0, padlock = 1
+
+    static func startStudy() {
+    }
+    
+    var name: String {
+        get {
+            return "indicator"
+        }
+    }
+    
+    var keyName: String {
+        get {
+            return "indicator mode"
+        }
+    }
+    
+    var numberOfTreatments: UInt32 {
+        get {
+            return 2
+        }
+    }
+    
+    
+    func imageOfSecureIndicator(background: Bool = false, open: Bool = false) -> UIImage {
+        switch self {
+        case .letter:
+            if open {
+                return IconsStyleKit.imageOfLetterOpen
+            }
+            if background {
+                return IconsStyleKit.imageOfLetterBG
+            }
+            return IconsStyleKit.imageOfLetter
+        case .padlock:
+            return IconsStyleKit.imageOfPadlockSecure
+        }
+    }
+    
+    
+    func imageOfCorruptedIndicator(background: Bool = false) -> UIImage {
+        switch self {
+        case .letter:
+            return IconsStyleKit.imageOfLetterCorrupted
+        case .padlock:
+            return IconsStyleKit.imageOfPadlockError
+        }
+    }
+    
+    func imageOfInsecureIndicator(background: Bool = false) -> UIImage {
+        switch self {
+        case .letter:
+            if background {
+                return IconsStyleKit.imageOfPostcardBG
+            }
+            return IconsStyleKit.imageOfPostcard
+        case .padlock:
+            return IconsStyleKit.imageOfPadlockInsecure
+        }
+    }
+    
+    func drawOfSecureIndictor(frame: CGRect?, rezising: IconsStyleKit.ResizingBehavior = .aspectFit, color: UIColor = IconsStyleKit.strokeColor, fillbackground: Bool = false, open: Bool) {
+        switch self {
+        case .letter:
+            if open {
+                var f = CGRect(x: 0, y: 0, width: 47, height: 43)
+                if let frame = frame {
+                    f = frame
+                }
+                IconsStyleKit.drawLetterOpen(frame: f, resizing: rezising, color: color)
+            }
+            else {
+                var f = CGRect(x: 0, y: 0, width: 50, height: 35)
+                if let frame = frame {
+                    f = frame
+                }
+                IconsStyleKit.drawLetter(frame: f, resizing: .aspectFit, color: color, fillBackground: fillbackground)
+            }
+            break
+        case .padlock:
+            var f = CGRect(x: 0, y: 0, width: 80, height: 100)
+            if let frame = frame {
+                f = frame
+            }
+            IconsStyleKit.drawPadlockSecure(frame: f, resizing: rezising, color: color, fillBackground: fillbackground)
+        }
+    }
+    
+     func drawOfInSecureIndictor(frame: CGRect?, rezising: IconsStyleKit.ResizingBehavior = .aspectFit, color: UIColor = IconsStyleKit.strokeColor, fillbackground: Bool = false, open: Bool) {
+        switch self {
+        case .letter:
+            var f = CGRect(x: 0, y: 0, width: 49, height: 34)
+            if let frame = frame {
+                f = frame
+            }
+            IconsStyleKit.drawPostcard(frame: f, resizing: rezising, color: color, fillBackground: fillbackground)
+            break
+        case .padlock:
+            var f = CGRect(x: 0, y: 0, width: 80, height: 100)
+            if let frame = frame {
+                f = frame
+            }
+            IconsStyleKit.drawPadlockInsecure(frame: f, resizing: rezising, color: color, fillBackground: fillbackground)
+        }
+    }
+    
+     func drawOfCorruptedIndictor(frame: CGRect?, rezising: IconsStyleKit.ResizingBehavior = .aspectFit, color: UIColor = IconsStyleKit.strokeColor, fillbackground: Bool = false, open: Bool) {
+        switch self {
+        case .letter:
+            var f = CGRect(x: 0, y: 0, width: 49, height: 34)
+            if let frame = frame {
+                f = frame
+            }
+            IconsStyleKit.drawLetterCorrupted(frame: f, resizing: rezising, color: color)
+            break
+        case .padlock:
+            var f = CGRect(x: 0, y: 0, width: 80, height: 100)
+            if let frame = frame {
+                f = frame
+            }
+            IconsStyleKit.drawPadlockError(frame: f, resizing: rezising, color: color, fillBackground: fillbackground)
+        }
+    }
+    
+}
diff --git a/enzevalos_iphone/study parameters/StudyParameterProtocol.swift b/enzevalos_iphone/study parameters/StudyParameterProtocol.swift
new file mode 100644
index 0000000000000000000000000000000000000000..b67e66efd8339c00bdbe1cc3912bf6430ddccf74
--- /dev/null
+++ b/enzevalos_iphone/study parameters/StudyParameterProtocol.swift	
@@ -0,0 +1,16 @@
+//
+//  StudyParameterProtocol.swift
+//  enzevalos_iphone
+//
+//  Created by Oliver Wiese on 22.01.19.
+//  Copyright © 2019 fu-berlin. All rights reserved.
+//
+
+import Foundation
+
+protocol StudyParameterProtocol {
+    var name: String {get}
+    var keyName: String {get}
+    var numberOfTreatments: UInt32 {get}
+    static func startStudy()
+}