using System;

using System.Collections.Generic;

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

public class Program

{

    public static void Main()

    {

        string json = @"

            {

              ""Vault"": 1,

              ""Transaction"": {

                ""gateway"": {

                  ""Login"": ""Nick"",

                  ""Password"": ""Password""

                },

                ""credit_card"": {

                  ""number"": ""4111111111111""

                }

              }

            }";

        JToken token = JToken.Parse(json);

        string[] jsonPaths = ExampleConfigSettings.GetJsonPathsToObscure();

        JsonHelper.ObscureMatchingValues(token, jsonPaths);

        ExampleLogger.Log(token.ToString(Formatting.None));

    }

}

​

public static class JsonHelper

{

    public static void ObscureMatchingValues(JToken token, IEnumerable<string> jsonPaths)

    {

        foreach (string path in jsonPaths)

        {

            foreach (JToken match in token.SelectTokens(path))

            {

                match.Replace(new JValue(Obscure(match.ToString())));

            }

        }

    }

    public static string Obscure(string s)

    {

        if (string.IsNullOrEmpty(s)) return s;

        int len = s.Length;

        int leftLen = len > 4 ? 1 : 0;

        int rightLen = len > 6 ? Math.Min((len - 6) / 2, 4) : 0;

        return s.Substring(0, leftLen) +

            new string('*', len - leftLen - rightLen) +

            s.Substring(len - rightLen);

    }

}

​

public static class ExampleConfigSettings

{

    public static string[] GetJsonPathsToObscure()

    {

        // In real code this would read the paths from a config file

        return new string[] { "$..Password", "$..credit_card.number" };

    }

}

​

public static class ExampleLogger

{

    public static void Log(string s)

    {

        // In real code this would write to a file or SQL table

        Console.WriteLine(DateTime.UtcNow.ToString("yyyy-MM-dd HH:mm:ss.fff") + " - " + s); 

    }

}