diff --git a/Signal/src/ViewControllers/Registration/OnboardingAccountDetailsViewController.swift b/Signal/src/ViewControllers/Registration/OnboardingAccountDetailsViewController.swift
index 6d67e58a3..0039e4257 100644
--- a/Signal/src/ViewControllers/Registration/OnboardingAccountDetailsViewController.swift
+++ b/Signal/src/ViewControllers/Registration/OnboardingAccountDetailsViewController.swift
@@ -1,13 +1,13 @@
 
 final class OnboardingAccountDetailsViewController : OnboardingBaseViewController {
     
-    private lazy var displayNameTextField: UITextField = {
+    private lazy var userNameTextField: UITextField = {
         let result = UITextField()
         result.textColor = Theme.primaryColor
         result.font = UIFont.ows_dynamicTypeBodyClamped
         result.textAlignment = .center
         result.placeholder = NSLocalizedString("Display Name (Optional)", comment: "")
-        result.accessibilityIdentifier = "onboarding.accountDetailsStep.displayNameTextField"
+        result.accessibilityIdentifier = "onboarding.accountDetailsStep.userNameTextField"
         return result
     }()
     
@@ -22,8 +22,8 @@ final class OnboardingAccountDetailsViewController : OnboardingBaseViewControlle
         return result
     }()
 
-    private var normalizedName: String? {
-        let result = displayNameTextField.text!.ows_stripped()
+    private var normalizedUserName: String? {
+        let result = userNameTextField.text!.ows_stripped()
         return !result.isEmpty ? result : nil
     }
     
@@ -46,7 +46,7 @@ final class OnboardingAccountDetailsViewController : OnboardingBaseViewControlle
             topSpacer,
             displayNameLabel,
             UIView.spacer(withHeight: 8),
-            displayNameTextField,
+            userNameTextField,
             UIView.spacer(withHeight: 16),
             passwordLabel,
             UIView.spacer(withHeight: 8),
@@ -67,15 +67,15 @@ final class OnboardingAccountDetailsViewController : OnboardingBaseViewControlle
     
     public override func viewDidAppear(_ animated: Bool) {
         super.viewDidAppear(animated)
-        displayNameTextField.becomeFirstResponder()
+        userNameTextField.becomeFirstResponder()
     }
     
     @objc private func handleNextButtonPressed() {
-        if let normalizedName = normalizedName {
+        if let normalizedName = normalizedUserName {
             guard !OWSProfileManager.shared().isProfileNameTooLong(normalizedName) else {
                 return OWSAlerts.showErrorAlert(message: NSLocalizedString("PROFILE_VIEW_ERROR_PROFILE_NAME_TOO_LONG", comment: "Error message shown when user tries to update profile with a profile name that is too long"))
             }
         }
-        onboardingController.pushKeyPairViewController(from: self, userName: normalizedName)
+        onboardingController.pushKeyPairViewController(from: self, userName: normalizedUserName)
     }
 }
diff --git a/Signal/src/ViewControllers/Registration/OnboardingKeyPairViewController.swift b/Signal/src/ViewControllers/Registration/OnboardingKeyPairViewController.swift
index 11f06259b..c4c6b4b0f 100644
--- a/Signal/src/ViewControllers/Registration/OnboardingKeyPairViewController.swift
+++ b/Signal/src/ViewControllers/Registration/OnboardingKeyPairViewController.swift
@@ -42,12 +42,22 @@ final class OnboardingKeyPairViewController : OnboardingBaseViewController {
     }()
     
     private lazy var restoreStackView: UIStackView = {
-        let result = UIStackView(arrangedSubviews: [ mnemonicTextField, UIView.spacer(withHeight: 24), registerButton ])
+        let result = UIStackView(arrangedSubviews: [ errorLabel, UIView.spacer(withHeight: 32), mnemonicTextField, UIView.spacer(withHeight: 24), registerButton ])
         result.accessibilityIdentifier = "onboarding.keyPairStep.restoreStackView"
         result.axis = .vertical
         return result
     }()
     
+    private lazy var errorLabel: UILabel = {
+        let result = createExplanationLabel(text: "")
+        result.accessibilityIdentifier = "onboarding.keyPairStep.errorLabel"
+        result.textColor = UIColor.red
+        var fontTraits = result.font.fontDescriptor.symbolicTraits
+        fontTraits.insert(.traitBold)
+        result.font = UIFont(descriptor: result.font.fontDescriptor.withSymbolicTraits(fontTraits)!, size: result.font.pointSize)
+        return result
+    }()
+    
     private lazy var mnemonicTextField: UITextField = {
         let result = UITextField(frame: CGRect.zero)
         result.accessibilityIdentifier = "onboarding.keyPairStep.mnemonicTextField"
@@ -129,16 +139,16 @@ final class OnboardingKeyPairViewController : OnboardingBaseViewController {
     
     // MARK: Updating
     private func handleModeChanged() {
+        UIView.animate(withDuration: 0.25) {
+            self.registerStackView.alpha = (self.mode == .register ? 1 : 0)
+            self.restoreStackView.alpha = (self.mode == .restore ? 1 : 0)
+        }
         let registerOrRestoreButtonTitle: String = {
             switch mode {
             case .register: return NSLocalizedString("Register", comment: "")
             case .restore: return NSLocalizedString("Restore", comment: "")
             }
         }()
-        UIView.animate(withDuration: 0.25) {
-            self.registerStackView.alpha = (self.mode == .register ? 1 : 0)
-            self.restoreStackView.alpha = (self.mode == .restore ? 1 : 0)
-        }
         self.registerOrRestoreButton.setTitle(registerOrRestoreButtonTitle)
     }
     
@@ -180,10 +190,14 @@ final class OnboardingKeyPairViewController : OnboardingBaseViewController {
             do {
                 let hexEncodedPrivateKey = try Mnemonic.decode(mnemonic: mnemonic)
                 let keyPair = ECKeyPair.generate(withHexEncodedPrivateKey: hexEncodedPrivateKey)
-                // TODO: Store key pair
+                let databaseConnection = OWSIdentityManager.shared().value(forKey: "dbConnection") as! YapDatabaseConnection
+                databaseConnection.setObject(keyPair, forKey: "TSStorageManagerIdentityKeyStoreIdentityKey", inCollection: OWSPrimaryStorageIdentityKeyStoreCollection)
                 hexEncodedPublicKey = keyPair.hexEncodedPublicKey
             } catch let error {
-                fatalError(error.localizedDescription) // TODO: Handle
+                let error = error as? Mnemonic.DecodingError ?? Mnemonic.DecodingError.generic
+                errorLabel.text = error.description
+                errorLabel.isHidden = false
+                return
             }
         }
         let accountManager = TSAccountManager.sharedInstance()
diff --git a/Signal/src/util/Mnemonic.swift b/Signal/src/util/Mnemonic.swift
index 0ef519d7d..e636f7395 100644
--- a/Signal/src/util/Mnemonic.swift
+++ b/Signal/src/util/Mnemonic.swift
@@ -45,6 +45,16 @@ enum Mnemonic {
     
     enum DecodingError : Error {
         case generic, inputTooShort, missingLastWord, invalidWord, verificationFailed
+        
+        var description: String {
+            switch self {
+            case .generic: return NSLocalizedString("Something went wrong. Please check your mnemonic and try again.", comment: "")
+            case .inputTooShort: return NSLocalizedString("Looks like you didn't enter enough words. Please check your mnemonic and try again.", comment: "")
+            case .missingLastWord: return NSLocalizedString("You seem to be missing the last word of your mnemonic. Please check what you entered and try again.", comment: "")
+            case .invalidWord: return NSLocalizedString("There appears to be an invalid word in your mnemonic. Please check what you entered and try again.", comment: "")
+            case .verificationFailed: return NSLocalizedString("Your mnemonic couldn't be verified. Please check what you entered and try again.", comment: "")
+            }
+        }
     }
     
     static func encode(hexEncodedString string: String, language: Language = .english) -> String {