%% You should probably cite rfc2634 instead of this I-D.
@techreport{ietf-smime-ess-12,
    number =    {draft-ietf-smime-ess-12},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-ietf-smime-ess/12/},
    author =    {Paul E. Hoffman},
    title =     {{Enhanced Security Services for S/MIME}},
    pagetotal = 58,
    year =      1999,
    month =     mar,
    day =       30,
    abstract =  {This document describes four optional security service extensions for S/MIME. {[}STANDARDS-TRACK{]}},
}