%% You should probably cite draft-ietf-dane-smime instead of this I-D.
@techreport{hoffman-dane-smime-04,
    number =    {draft-hoffman-dane-smime-04},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-hoffman-dane-smime/04/},
    author =    {Paul E. Hoffman and Jakob Schlyter},
    title =     {{Using Secure DNS to Associate Certificates with Domain Names For S/MIME}},
    pagetotal = 6,
    year =      2012,
    month =     sep,
    day =       8,
    abstract =  {This document describes how to use secure DNS to associate an S/MIME user's certificate with the intended domain name, similar to the way that DANE (RFC 6698) does for TLS.},
}