diff --git a/VoiceInk/Services/Obfuscator.swift b/VoiceInk/Services/Obfuscator.swift
new file mode 100644
index 0000000..777860e
--- /dev/null
+++ b/VoiceInk/Services/Obfuscator.swift
@@ -0,0 +1,62 @@
+import Foundation
+import IOKit
+
+/// Simple utility to obfuscate sensitive data stored in UserDefaults
+struct Obfuscator {
+    
+    /// Encodes a string using Base64 with a device-specific salt
+    static func encode(_ string: String, salt: String) -> String {
+        let salted = salt + string + salt
+        let data = Data(salted.utf8)
+        return data.base64EncodedString()
+    }
+    
+    /// Decodes a Base64 string using a device-specific salt
+    static func decode(_ base64: String, salt: String) -> String? {
+        guard let data = Data(base64Encoded: base64),
+              let salted = String(data: data, encoding: .utf8) else {
+            return nil
+        }
+        
+        // Remove the salt from both ends
+        guard salted.hasPrefix(salt), salted.hasSuffix(salt) else { 
+            return nil 
+        }
+        
+        return String(salted.dropFirst(salt.count).dropLast(salt.count))
+    }
+    
+    /// Gets a device-specific identifier to use as salt
+    /// Uses the same logic as PolarService for consistency
+    static func getDeviceIdentifier() -> String {
+        // Try to get Mac serial number first
+        if let serialNumber = getMacSerialNumber() {
+            return serialNumber
+        }
+        
+        // Fallback to stored UUID
+        let defaults = UserDefaults.standard
+        if let storedId = defaults.string(forKey: "VoiceInkDeviceIdentifier") {
+            return storedId
+        }
+        
+        // Create and store new UUID
+        let newId = UUID().uuidString
+        defaults.set(newId, forKey: "VoiceInkDeviceIdentifier")
+        return newId
+    }
+    
+    /// Try to get the Mac serial number
+    private static func getMacSerialNumber() -> String? {
+        let platformExpert = IOServiceGetMatchingService(kIOMainPortDefault, IOServiceMatching("IOPlatformExpertDevice"))
+        if platformExpert == 0 { return nil }
+        
+        defer { IOObjectRelease(platformExpert) }
+        
+        if let serialNumber = IORegistryEntryCreateCFProperty(platformExpert, "IOPlatformSerialNumber" as CFString, kCFAllocatorDefault, 0) {
+            return (serialNumber.takeRetainedValue() as? String)?.trimmingCharacters(in: .whitespacesAndNewlines)
+        }
+        
+        return nil
+    }
+}
diff --git a/VoiceInk/Services/PolarService.swift b/VoiceInk/Services/PolarService.swift
index 9ac4bbd..4110768 100644
--- a/VoiceInk/Services/PolarService.swift
+++ b/VoiceInk/Services/PolarService.swift
@@ -36,37 +36,9 @@ class PolarService {
         let status: String
     }
     
-    // Generate a unique device identifier
+    // Generate a unique device identifier using shared logic
     private func getDeviceIdentifier() -> String {
-        // Use the macOS serial number or a generated UUID that persists
-        if let serialNumber = getMacSerialNumber() {
-            return serialNumber
-        }
-        
-        // Fallback to a stored UUID if we can't get the serial number
-        let defaults = UserDefaults.standard
-        if let storedId = defaults.string(forKey: "VoiceInkDeviceIdentifier") {
-            return storedId
-        }
-        
-        // Create and store a new UUID if none exists
-        let newId = UUID().uuidString
-        defaults.set(newId, forKey: "VoiceInkDeviceIdentifier")
-        return newId
-    }
-    
-    // Try to get the Mac serial number
-    private func getMacSerialNumber() -> String? {
-        let platformExpert = IOServiceGetMatchingService(kIOMainPortDefault, IOServiceMatching("IOPlatformExpertDevice"))
-        if platformExpert == 0 { return nil }
-        
-        defer { IOObjectRelease(platformExpert) }
-        
-        if let serialNumber = IORegistryEntryCreateCFProperty(platformExpert, "IOPlatformSerialNumber" as CFString, kCFAllocatorDefault, 0) {
-            return (serialNumber.takeRetainedValue() as? String)?.trimmingCharacters(in: .whitespacesAndNewlines)
-        }
-        
-        return nil
+        return Obfuscator.getDeviceIdentifier()
     }
     
     // Check if a license key requires activation
diff --git a/VoiceInk/Services/UserDefaultsManager.swift b/VoiceInk/Services/UserDefaultsManager.swift
index 2c85b64..4315a11 100644
--- a/VoiceInk/Services/UserDefaultsManager.swift
+++ b/VoiceInk/Services/UserDefaultsManager.swift
@@ -8,6 +8,11 @@ extension UserDefaults {
         static let audioInputMode = "audioInputMode"
         static let selectedAudioDeviceUID = "selectedAudioDeviceUID"
         static let prioritizedDevices = "prioritizedDevices"
+        
+        // Obfuscated keys for license-related data
+        enum License {
+            static let trialStartDate = "VoiceInkTrialStartDate"
+        }
     }
     
     // MARK: - AI Provider API Key
@@ -22,10 +27,32 @@ extension UserDefaults {
         set { setValue(newValue, forKey: Keys.licenseKey) }
     }
     
-    // MARK: - Trial Start Date
+    // MARK: - Trial Start Date (Obfuscated)
     var trialStartDate: Date? {
-        get { object(forKey: Keys.trialStartDate) as? Date }
-        set { setValue(newValue, forKey: Keys.trialStartDate) }
+        get {
+            let salt = Obfuscator.getDeviceIdentifier()
+            let obfuscatedKey = Obfuscator.encode(Keys.License.trialStartDate, salt: salt)
+            
+            guard let obfuscatedValue = string(forKey: obfuscatedKey),
+                  let decodedValue = Obfuscator.decode(obfuscatedValue, salt: salt),
+                  let timestamp = Double(decodedValue) else {
+                return nil
+            }
+            
+            return Date(timeIntervalSince1970: timestamp)
+        }
+        set {
+            let salt = Obfuscator.getDeviceIdentifier()
+            let obfuscatedKey = Obfuscator.encode(Keys.License.trialStartDate, salt: salt)
+            
+            if let date = newValue {
+                let timestamp = String(date.timeIntervalSince1970)
+                let obfuscatedValue = Obfuscator.encode(timestamp, salt: salt)
+                setValue(obfuscatedValue, forKey: obfuscatedKey)
+            } else {
+                removeObject(forKey: obfuscatedKey)
+            }
+        }
     }
 
     // MARK: - Audio Input Mode