Raybbo Raybbo - 1 year ago 220
ASP.NET (C#) Question

"Error occurred during a cryptographic operation" when decrypting Forms cookie

I've uploaded my website to a webhosting and this error came up;

'Error occurred during a cryptographic operation.'.

I've done some research and it seems that the formauthenticated cookie is bound to the MachineKey (which differs when using webhost).

I've found a method that should fix this problem but the error remains.


/// <summary>
/// This method removes a cookie if the machine key is different than the one that saved the cookie;
/// </summary>
protected void Application_Error(object sender, EventArgs e)
var error = Server.GetLastError();
var cryptoEx = error as CryptographicException;
if (cryptoEx != null)
Global.Cookies.FormAuthenticated Cookie = new Global.Cookies.FormAuthenticated();


[CryptographicException: Error occurred during a cryptographic operation.]
System.Web.Security.Cryptography.HomogenizingCryptoServiceWrapper.HomogenizeErrors(Func`2 func, Byte[] input) +115
System.Web.Security.Cryptography.HomogenizingCryptoServiceWrapper.Unprotect(Byte[] protectedData) +59
System.Web.Security.FormsAuthentication.Decrypt(String encryptedTicket) +9824926
Archive_Template.Main.resolveLoginUser(String sessionKey) in f:\Archive_Template\Archive_Template\Main.aspx.cs:481
Archive_Template.Main.OnPreInit(EventArgs e) in f:\Archive_Template\Archive_Template\Main.aspx.cs:52
System.Web.UI.Page.PerformPreInit() +31
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +335

Answer Source

For anyone who hasn't solved their problem, I was missing the "machineKey" entry for encrypt/decrypt in my web.config

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