how to generate a unique token which expires after 24 hours

Question

I have a WCF Webservice which checks if the user is valid    If the user is valid I want to generate a token which expires after 24 hours   public bool authenticateUserManual string userName  string password string language string token        if  Membership ValidateUser userName password                                    string token                                     return true            else                return false

User · Answer

This way a token will exist up-to 24 hours  here is the code to generate token which will valid up-to 24 Hours  this code we use but i did not compose it  public static string GenerateToken         int month   DateTime Now Month      int day   DateTime Now Day      string token     day   100   month    700   day   13  ToString        return token

User · Answer

I like Guffa s answer and since I can t comment I will provide the answer Udil s question here  I needed something similar but I wanted certein logic in my token  I wanted to   See the expiration of a token Use a guid to mask validate  global application guid or user guid  See if the token was provided for the purpose I created it  no reuse    See if the user I send the token to is the user that I am validating it for  Now points 1-3 are fixed length so it was easy  here is my code  Here is my code to generate the token  public string GenerateToken string reason  MyUser user        byte    time       BitConverter GetBytes DateTime UtcNow ToBinary         byte    key        Guid Parse user SecurityStamp  ToByteArray        byte    Id         GetBytes user Id ToString         byte    reason     GetBytes reason       byte   data         new byte  time Length    key Length    reason Length  Id Length        System Buffer BlockCopy  time  0  data  0   time Length       System Buffer BlockCopy  key   0  data   time Length   key Length       System Buffer BlockCopy  reason  0  data   time Length    key Length   reason Length       System Buffer BlockCopy  Id  0  data   time Length    key Length    reason Length   Id Length        return Convert ToBase64String data ToArray        Here is my Code to take the generated token string and validate it  public TokenValidation ValidateToken string reason  MyUser user  string token        var result   new TokenValidation        byte   data       Convert FromBase64String token       byte    time       data Take 8  ToArray        byte    key        data Skip 8  Take 16  ToArray        byte    reason     data Skip 24  Take 2  ToArray        byte    Id         data Skip 26  ToArray         DateTime when   DateTime FromBinary BitConverter ToInt64  time  0        if  when  lt  DateTime UtcNow AddHours -24                 result Errors Add  TokenValidationStatus Expired                  Guid gKey   new Guid  key       if  gKey ToString      user SecurityStamp                result Errors Add TokenValidationStatus WrongGuid              if  reason    GetString  reason                 result Errors Add TokenValidationStatus WrongPurpose              if  user Id ToString      GetString  Id                 result Errors Add TokenValidationStatus WrongUser                  return result     private static string GetString byte   reason    gt  Encoding ASCII GetString reason    private static byte   GetBytes string reason    gt  Encoding ASCII GetBytes reason    The TokenValidation class looks like this  public class TokenValidation       public bool Validated   get   return Errors Count    0          public readonly List lt TokenValidationStatus gt  Errors   new List lt TokenValidationStatus gt        public enum TokenValidationStatus       Expired      WrongUser      WrongPurpose      WrongGuid    Now I have an easy way to validate a token  no Need to Keep it in a list for 24 hours or so  Here is my Good-Case Unit test  private const string ResetPasswordTokenPurpose    quot RP quot   private const string ConfirmEmailTokenPurpose     quot EC quot    change here change bit length for reason  section  2 per char    TestMethod  public void GenerateTokenTest         MyUser user           CreateTestUser  quot name quot        user Id               123      user SecurityStamp    Guid NewGuid   ToString        var token     sit GenerateToken ConfirmEmailTokenPurpose  user       var validation      sit ValidateToken ConfirmEmailTokenPurpose  user  token       Assert IsTrue validation Validated  quot Token validated for user 123 quot       One can adapt the code for other business cases easely  Happy Coding Walter

User · Answer

Use Dictionary lt string  DateTime gt  to store token with timestamp   static Dictionary lt string  DateTime gt  dic   new Dictionary lt string  DateTime gt       Add token with timestamp whenever you create new token   dic Add  yourToken   DateTime Now     There is a timer running to remove any expired tokens out of dic    timer   new Timer 1000 60     assume run in 1 minute  timer Elapsed    timer Elapsed    static void timer Elapsed object sender  ElapsedEventArgs e                var expiredTokens   dic Where p   gt  p Value AddDays 1   lt   DateTime Now                                 Select p   gt  p Key            foreach  var key in expiredTokens              dic Remove key           So  when you authenticate token  just check whether token exists in dic or not

User · Answer

you need to store the token while creating for 1st registration  When you retrieve data from login table you need to differentiate entered date with current date if it is more than 1 day  24 hours  you need to display message like your token is expired   To generate key refer here

User · Answer

There are two possible approaches  either you create a unique value and store somewhere along with the creation time  for example in a database  or you put the creation time inside the token so that you can decode it later and see when it was created   To create a unique token   string token   Convert ToBase64String Guid NewGuid   ToByteArray       Basic example of creating a unique token containing a time stamp   byte   time   BitConverter GetBytes DateTime UtcNow ToBinary     byte   key   Guid NewGuid   ToByteArray    string token   Convert ToBase64String time Concat key  ToArray       To decode the token to get the creation time   byte   data   Convert FromBase64String token   DateTime when   DateTime FromBinary BitConverter ToInt64 data  0    if  when  lt  DateTime UtcNow AddHours -24          too old     Note  If you need the token with the time stamp to be secure  you need to encrypt it  Otherwise a user could figure out what it contains and create a false token

[c#] how to generate a unique token which expires after 24 hours?

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