Invalid length for a Base-64 char array

Question

As the title says  I am getting       Invalid length for a Base-64 char   array    I have read about this problem on here and it seems that the  suggestion is to store ViewState in SQL if it is large  I am  using a wizard with a good deal of data collection so chances are my ViewState is large  But  before I turn to the  store-in-DB  solution  maybe somebody can take a look and tell me if I have  other options   I construct the email for delivery using the below method   public void SendEmailAddressVerificationEmail string userName  string to        string msg    Please click on the link below or paste it into a browser to verify your email account  lt BR gt  lt BR gt                           lt a href        configuration RootURL    Accounts VerifyEmail aspx a                         userName Encrypt  verify         gt                          configuration RootURL    Accounts VerifyEmail aspx a                         userName Encrypt  verify       lt  a gt         SendEmail to           Account created  Email verification required    msg       The Encrypt method looks like this    public static string Encrypt string clearText  string Password         byte   clearBytes   System Text Encoding Unicode GetBytes clearText        PasswordDeriveBytes pdb   new PasswordDeriveBytes Password  new byte     0x49  0x76  0x61  0x6e  0x20  0x4d  0x65  0x64  0x76  0x65  0x64  0x65  0x76           byte   encryptedData   Encrypt clearBytes  pdb GetBytes 32   pdb GetBytes 16         return Convert ToBase64String encryptedData       Here is what the HTML looks like in hotmail      Please click on the link below or   paste it into a browser to verify your   email account       http   localhost 1563 Accounts VerifyEmail aspx a YOHY57xYRENEOu3H FGq1Rf09AZAI56EPjfwuK8XWKg    On the receiving end  the VerifyEmail aspx cs page has the line    string username   Cryptography Decrypt  webContext UserNameToVerify   verify      Here is the getter for UserNameToVerify   public string UserNameToVerify       get               return GetQueryStringValue  a   ToString              And here is the GetQueryStringValue method   private static string GetQueryStringValue string key        return HttpContext Current Request QueryString Get key       And the decrypt method looks like   public static string Decrypt string cipherText  string password              THE ERROR IS THROWN HERE         byte   cipherBytes   Convert FromBase64String cipherText     Can this error be remedied with a code fix or must I store ViewState in the database

User · Answer

I m not Reputable enough to upvote or comment yet  but LukeH s answer was spot on for me   As AES encryption is the standard to use now  it produces a base64 string  at least all the encrypt decrypt implementations I ve seen    This string has a length in multiples of 4  string length   4   0   The strings I was getting contained   and   on the beginning or end  and when you just concatenate that into a URL s querystring  it will look right  for instance  in an email you generate   but when the the link is followed and the  NET page recieves it and puts it into this Page Request QueryString  those special characters will be gone and your string length will not be in a multiple of 4   As the are special characters at the FRONT of the string  ex      as well as   at the end  you can t just add some   to make up the difference as you are altering the cypher text in a way that doesn t match what was actually in the original querystring   So  wrapping the cypher text with HttpUtility URLEncode  not HtmlEncode  transforms the non-alphanumeric characters in a way that ensures  NET parses them back into their original state when it is intepreted into the querystring collection   The good thing is  we only need to do the URLEncode when generating the querystring for the URL   On the incoming side  it s automatically translated back into the original string value   Here s some example code  string cryptostring   MyAESEncrypt MySecretString   string URL   WebFunctions ToAbsoluteUrl    ResetPassword aspx RPC     HttpUtility UrlEncode cryptostring

User · Answer

The length of a base64 encoded string is always a multiple of 4   If it is not a multiple of 4  then   characters are appended until it is   A query string of the form  name value has problems when the value contains   charaters  some of them will be dropped  I don t recall the exact behavior    You may be able to get away with appending the right number of   characters before doing the base64 decode   Edit 1  You may find that the value of UserNameToVerify has had     s changed to     s so you may need to do something like so   a   a Replace              This should get the length right   int mod4   a Length   4  if  mod4  gt  0         a    new string      4 - mod4       Of course calling UrlEncode  as in LukeH s answer  should make this all moot

User · Answer

string stringToDecrypt   CypherText Replace                int len   stringToDecrypt Length      byte   inputByteArray   Convert FromBase64String stringToDecrypt

User · Answer

My guess is that you simply need to URL-encode your Base64 string when you include it in the querystring   Base64 encoding uses some characters which must be encoded if they re part of a querystring  namely   and    and maybe   too   If the string isn t correctly encoded then you won t be able to decode it successfully at the other end  hence the errors   You can use the HttpUtility UrlEncode method to encode your Base64 string   string msg    Please click on the link below or paste it into a browser                   to verify your email account  lt br   gt  lt br   gt  lt a href                     configuration RootURL    Accounts VerifyEmail aspx a                  HttpUtility UrlEncode userName Encrypt  verify          gt                   configuration RootURL    Accounts VerifyEmail aspx a                  HttpUtility UrlEncode userName Encrypt  verify        lt  a gt

User · Answer

The encrypted string had two special characters    and         sign was giving the error  so below solution worked well     replace   sign  encryted string   encryted string Replace        2b         2b  is HTTP encoded string for       sign   OR      encode special charactes   encryted string   HttpUtility UrlEncode encryted string      then pass it to the decryption process

User · Answer

My initial guess without knowing the data would be that the UserNameToVerify is not a multiple of 4 in length   Check out the FromBase64String on msdn      Ok byte   b1   Convert FromBase64String  CoolDude       Exception byte   b2   Convert FromBase64String  MyMan

[c#] Invalid length for a Base-64 char array

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