Problem with keys in EF mvc5 asp .net

I have defined the keys in each of those entities with the attribute [key] as you can see in the photo, apart from that the namespace is imported "using System.ComponentModel.DataAnnotations;" and when creating controllers this happens.

for this case, the traveling class is defined as follows:

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;

namespace OsAgenciaUSBT.Models
{
    public class Viajero
    {
        [key]
        public int IdViajero { get; set; }
        public string tipoViajero { get; set; }
        public string nombres { get; set; }
        public string Apellidos { get; set; }
        public int telefono { get; set; }

        [DataType(DataType.Date)]
        public DateTime Update { get { return DateTime.Now; } }


        public virtual ICollection<Venta> Venta { get; set; }
    }
}