System.ComponentModel.DataAnnotations.MetadataTypeAttribute is a handy bridge to attributes defined in other files, especially in code generated files. It works with the validation frameworks. I don't see why it wouldn't here.

Example:

[GeneratedCode]
[MetadataTypeAttribute(typeof(DtoMetadata))]
public partial class Dto
{
    public string Private { get; set; }
}

internal class DtoMetadata
{
     [NotLogged]
     public object Private { get; set; }
}

I think it would be great if both sources could be utilized, but the configuration on the primary class would win in the event of a conflict.