diff --git a/src/Amazon.Extensions.CognitoAuthentication/CognitoUser.cs b/src/Amazon.Extensions.CognitoAuthentication/CognitoUser.cs
index 5758708..a3a521b 100644
--- a/src/Amazon.Extensions.CognitoAuthentication/CognitoUser.cs
+++ b/src/Amazon.Extensions.CognitoAuthentication/CognitoUser.cs
@@ -123,13 +123,8 @@ public CognitoUser(string userID, string clientID,
             }
 
             this.ClientSecret = clientSecret;
-            if (!string.IsNullOrEmpty(clientSecret))
-            {
-                this.SecretHash = CognitoAuthHelper.GetUserPoolSecretHash(userID, clientID, clientSecret);
-            }
 
             this.UserID = userID;
-            this.Username = userID;
             if (!string.IsNullOrEmpty(username))
             {
                 this.Username = username;
@@ -139,6 +134,11 @@ public CognitoUser(string userID, string clientID,
                 this.Username = userID;
             }
 
+            if (!string.IsNullOrEmpty(clientSecret))
+            {
+                this.SecretHash = CognitoAuthHelper.GetUserPoolSecretHash(Username, clientID, clientSecret);
+            }
+
             this.Status = status;
 
             this.UserPool = pool;
diff --git a/src/Amazon.Extensions.CognitoAuthentication/CognitoUserAuthentication.cs b/src/Amazon.Extensions.CognitoAuthentication/CognitoUserAuthentication.cs
index 361ffd7..aa15a52 100644
--- a/src/Amazon.Extensions.CognitoAuthentication/CognitoUserAuthentication.cs
+++ b/src/Amazon.Extensions.CognitoAuthentication/CognitoUserAuthentication.cs
@@ -66,7 +66,7 @@ public virtual async Task<AuthFlowResponse> StartWithSrpAuthAsync(InitiateSrpAut
             if (srpRequest.IsCustomAuthFlow)
             {
                 initiateRequest.AuthFlow = AuthFlowType.CUSTOM_AUTH;
-                initiateRequest.AuthParameters.Add("CHALLENGE_NAME", "SRP_A");
+                initiateRequest.AuthParameters.Add(CognitoConstants.ChlgParamChallengeName, CognitoConstants.ChlgParamSrpA);
             }
             InitiateAuthResponse initiateResponse = await Provider.InitiateAuthAsync(initiateRequest, cancellationToken).ConfigureAwait(false);
             UpdateUsernameAndSecretHash(initiateResponse.ChallengeParameters);
@@ -132,7 +132,7 @@ private RespondToAuthChallengeRequest CreateDeviceSrpAuthRequest(RespondToAuthCh
             
             RespondToAuthChallengeRequest authChallengeRequest = new RespondToAuthChallengeRequest()
             {
-                ChallengeName = "DEVICE_SRP_AUTH",
+                ChallengeName = ChallengeNameType.DEVICE_SRP_AUTH,
                 ClientId = ClientID,
                 Session = challenge.Session,
                 ChallengeResponses = new Dictionary<string, string>
@@ -143,9 +143,8 @@ private RespondToAuthChallengeRequest CreateDeviceSrpAuthRequest(RespondToAuthCh
                 }
 
             };
-            if (!string.IsNullOrEmpty(ClientSecret))
+            if (!string.IsNullOrEmpty(SecretHash))
             {
-                SecretHash = CognitoAuthHelper.GetUserPoolSecretHash(Username, ClientID, ClientSecret);
                 authChallengeRequest.ChallengeResponses.Add(CognitoConstants.ChlgParamSecretHash, SecretHash);
             }
             return authChallengeRequest;
@@ -192,9 +191,8 @@ private RespondToAuthChallengeRequest CreateDevicePasswordVerifierAuthRequest(Re
                 {CognitoConstants.ChlgParamDeviceKey, Device.DeviceKey }
             };
 
-            if (!string.IsNullOrEmpty(ClientSecret))
+            if (!string.IsNullOrEmpty(SecretHash))
             {
-                SecretHash = CognitoAuthHelper.GetUserPoolSecretHash(Username, ClientID, ClientSecret);
                 srpAuthResponses.Add(CognitoConstants.ChlgParamSecretHash, SecretHash);
             }
 
@@ -814,9 +812,8 @@ private RespondToAuthChallengeRequest CreateSrpPasswordVerifierAuthRequest(Initi
                 {CognitoConstants.ChlgParamTimestamp, timeStr },
             };
 
-            if (!string.IsNullOrEmpty(ClientSecret))
+            if (!string.IsNullOrEmpty(SecretHash))
             {
-                SecretHash = CognitoAuthHelper.GetUserPoolSecretHash(Username, ClientID, ClientSecret);
                 srpAuthResponses.Add(CognitoConstants.ChlgParamSecretHash, SecretHash);
             }