using System;

using System.Linq;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string text=@"""firstName"": ""AClinician"", 

""lastName"": ""Password\"": \""shouldbe \""secret\"": \""Hello "" 

 ""MyPassword"":""860-234-1234"", ""MySecreta"":  ""860-234-1234"" 

 ""Authorization"":   ""bearer"",

 ""secret"" :  ""860\\6

 6\\""\\6"",

 ""Cookie"":   ""session-id=abcd"", ""Set-Cookie"": ""session-id=12345""

 ""lastName""   : ""My last name  \""Password\"" : \""Will Stay unmask\""  ""SendResetPassword"": true   

​

} ";

            string prefix = @"""[a-zA-Z]*";

            string suffix = @"[a-zA-Z]*""";

​

            var terms = string.Join( "|",

                              (new string[] { "password", "secret", "authorization", "Cookie", "Set-Cookie" })

                                    .Select(s => prefix + s + suffix).ToList());

​

            //string pattern = @"(?im)(" + terms + @")\s?(:[=""\s]*)""(?:.*?)[^""]""([^""][""\s])";

        string pattern=  @"(?im)(" + terms + @")\s?(:[=""\s]*)""(?:(.*[\\][""].*?)|(.*?[\\].*?)|(.*?))(?:"")";

            string replace = @"$1$2""***""";

           Console.WriteLine( Regex.Replace(text, pattern, replace) );

           Console.WriteLine( Regex.Replace( 

               @"""Headers"":{""Set-Cookie"":""session-id=\""EAAAAI8vcVykYpGJ1J2NmziPU % 2fuz4R\\"" \\''\\""inasl % 2fpmS % 2bYUCXMYxQBfqvDOtTFBi9kzRbKR66wkQOZtjLlRhNdgEp % 2fMHk % 2f5M % 3d; expires = Wed, 16 Nov 2016 09:34:23 GMT; domain = cognigramdevci1api.azurewebsites.net; path =/; secure; httponly"", ""Not-Cookie"": ""Hello""},"

            , pattern, replace));

    }

}