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Posted 3 Apr 2006

HttpSecureCookie, A Way to Encrypt Cookies with ASP.NET 2.0

, 3 Apr 2006
Discussing how to encode and tamper-proof text and cookies using the MachineKey, by using reflection.
using System;
using System.Web;
using System.Web.Security;
using System.Reflection;

namespace AdamTibi.Web.Security {

    /// <summary>
    /// A wrapper arroud System.Web.Security.CookieProtectionHelper internal class
    /// </summary>
    public static class CookieProtectionHelperWrapper {

        private static MethodInfo _encode;
        private static MethodInfo _decode;

        /// <summary>
        /// Constructor
        /// </summary>
        static CookieProtectionHelperWrapper() {
            // obtaining a reference to System.Web assembly
            Assembly systemWeb = typeof(HttpContext).Assembly;
            if (systemWeb == null) {
                throw new InvalidOperationException("Unable to load System.Web.");
            // obtaining a reference to the internal class CookieProtectionHelper
            Type cookieProtectionHelper = systemWeb.GetType("System.Web.Security.CookieProtectionHelper");
            if (cookieProtectionHelper == null) {
                throw new InvalidOperationException("Unable to get the internal class System.Web.Security.CookieProtectionHelper.");
            // obtaining references to the methods of CookieProtectionHelper class
            _encode = cookieProtectionHelper.GetMethod("Encode", BindingFlags.NonPublic | BindingFlags.Static);
            _decode = cookieProtectionHelper.GetMethod("Decode", BindingFlags.NonPublic | BindingFlags.Static);

            if (_encode == null || _decode == null) {
                throw new InvalidOperationException("Unable to get the methods to invoke.");

        /// <summary>
        /// Wrapper arround CookieProtectionHelper.Encode
        /// </summary>
        /// <param name="cookieProtection">Protection Type</param>
        /// <param name="buf">Bytes buffer to encode</param>
        /// <param name="count">The number of bytes in the buffer</param>
        /// <returns>Encoded text</returns>
        public static string Encode(CookieProtection cookieProtection, byte[] buf, int count) {
            return (string)_encode.Invoke(null, new object[] { cookieProtection, buf, count });

        /// <summary>
        /// Wrapper arround CookieProtectionHelper.Decode
        /// </summary>
        /// <param name="cookieProtection">Protection Type</param>
        /// <param name="data">String to decode</param>
        /// <returns>Decoded bytes</returns>
        public static byte[] Decode(CookieProtection cookieProtection, string data) {
            return (byte[])_decode.Invoke(null, new object[] { cookieProtection, data });



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About the Author

Adam Tibi
United Kingdom United Kingdom
Passionate about refining software practices, promoting self-motivated teams and orchestrating agile projects.
Lives in London, UK and works as a .NET architect consultant in the City.

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Web03 | 2.8.171020.1 | Last Updated 3 Apr 2006
Article Copyright 2006 by Adam Tibi
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