Attribute to decorate the type declaration for a class that has auto encrypted properties

EncryptedTypeAttribute.cs

using System;
using System.Collections.Generic;
using System.Security.Cryptography;

using PostSharp.Aspects;
using PostSharp.Aspects.Advices;
using PostSharp.Aspects.Dependencies;

namespace DataAccess.Aspects {
    [Serializable]
    [AspectTypeDependency(AspectDependencyAction.Order, AspectDependencyPosition.Before, typeof(EncryptedAttribute))]
    [IntroduceInterface(typeof(IEncrypted), OverrideAction = InterfaceOverrideAction.Ignore)]
    [AttributeUsage(AttributeTargets.Class)]
    public class EncryptedTypeAttribute : InstanceLevelAspect, IEncrypted  {

        [IntroduceMember(IsVirtual=false,OverrideAction=MemberOverrideAction.OverrideOrFail, Visibility=PostSharp.Reflection.Visibility.Public)]
        public Dictionary<string, string> EncryptedValues { get; set; }
       
        public override void RuntimeInitialize(Type type) {
            EncryptedValues = new Dictionary<string, string>();
        }

        public object AsClear(string Name) {
            if (null != EncryptedValues) {
                if (EncryptedValues.ContainsKey(Name))
                    return System.Text.UnicodeEncoding.Unicode.GetString(ProtectedData.Unprotect(
                        Convert.FromBase64String(EncryptedValues[Name].Substring(136)), 
                        Convert.FromBase64String(EncryptedValues[Name].Substring(0, 136)), 
                        DataProtectionScope.CurrentUser));
            }
            return null;
        }
    }
}