diff --git a/Guardian/Generators/OneTimePasswordGenerator.swift b/Guardian/Generators/OneTimePasswordGenerator.swift
index 7d844e6..f14dbe6 100644
--- a/Guardian/Generators/OneTimePasswordGenerator.swift
+++ b/Guardian/Generators/OneTimePasswordGenerator.swift
@@ -82,17 +82,13 @@ struct OneTimePasswordGenerator: TOTP, HOTP {
         var c = UInt64(counter).bigEndian
         let buffer = Data(bytes: &c, count: MemoryLayout<UInt64>.size);
         let digestData = hmac.sign(buffer)
-        let hash = digestData.withUnsafeBytes { (bytes: UnsafePointer<UInt8>) -> UInt32 in
-            let last = bytes.advanced(by: hmac.digestLength - 1)
-            let offset = last.pointee & 0x0f
-            let start = bytes.advanced(by: Int(offset))
-            let value = start.withMemoryRebound(to: UInt32.self, capacity: 1) { $0 }
-            var hash = UInt32(bigEndian: value.pointee)
-            hash &= 0x7fffffff
-            hash = hash % UInt32(pow(10, Float(self.parameters.digits)))
-            return hash
-        }
-
+        let length = MemoryLayout<UInt32>.size
+        // digestData.count - 1 will always be >0, because digestData depends on algorythm and can be only 20, 32, or 64.
+        let offset = Int(digestData[digestData.count - 1] & 0x0f)
+        // offset is always <=15, length is always 4, so prefix will always be within digestData count.
+        var hash = digestData.dropFirst(offset).prefix(length).reduce(0, { $0 << 8 | UInt32($1) })
+        hash &= 0x7fffffff
+        hash = hash % UInt32(pow(10, Float(self.parameters.digits)))
         return Int(hash)
     }
 
diff --git a/GuardianApp/State.swift b/GuardianApp/State.swift
index 41b1069..b2e0efc 100644
--- a/GuardianApp/State.swift
+++ b/GuardianApp/State.swift
@@ -28,9 +28,9 @@ struct GuardianState: Codable {
 
     let identifier: String
     let localIdentifier: String
-    let token: String
     let keyTag: String
     let otp: OTPParameters?
+    let userId: String
 
     func save() throws {
         let encoder = JSONEncoder()
diff --git a/GuardianApp/ViewController.swift b/GuardianApp/ViewController.swift
index 7f4d6bd..424e973 100644
--- a/GuardianApp/ViewController.swift
+++ b/GuardianApp/ViewController.swift
@@ -93,7 +93,7 @@ class ViewController: UIViewController, QRCodeReaderViewControllerDelegate {
                     case .failure(let cause):
                         self.showError("Enroll failed", cause)
                     case .success(let enrollment):
-                        AppDelegate.state = GuardianState(identifier: enrollment.id, localIdentifier: enrollment.localIdentifier, token: enrollment.deviceToken, keyTag: signingKey.tag, otp: enrollment.totp)
+                        AppDelegate.state = GuardianState(identifier: enrollment.id, localIdentifier: enrollment.localIdentifier, keyTag: signingKey.tag, otp: enrollment.totp, userId: enrollment.userId)
                     }
                     self.updateView()
             }
@@ -119,7 +119,7 @@ class ViewController: UIViewController, QRCodeReaderViewControllerDelegate {
         if let enrollment = AppDelegate.state {
             let request = Guardian
                 .api(forDomain: AppDelegate.guardianDomain)
-                .device(forEnrollmentId: enrollment.identifier, token: enrollment.token)
+                .device(forEnrollmentId: enrollment.identifier, userId: enrollment.userId, signingKey: enrollment.signingKey)
                 .delete()
             debugPrint(request)
             request.start { [unowned self] result in