%% You should probably cite rfc7619 instead of this I-D.
@techreport{ietf-ipsecme-ikev2-null-auth-02,
    number =    {draft-ietf-ipsecme-ikev2-null-auth-02},
    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-ipsecme-ikev2-null-auth/02/},
    author =    {Valery Smyslov and Paul Wouters},
    title =     {{The NULL Authentication Method in IKEv2 Protocol}},
    pagetotal = 12,
    year =      2015,
    month =     jan,
    day =       13,
    abstract =  {This document specifies the NULL Authentication Method and the ID\_NULL Identification Payload ID Type for the IKEv2 Protocol. This allows two IKE peers to establish single-side authenticated or mutual un-authenticated IKE sessions for those use cases where a peer is unwilling or unable to authenticate itself. This ensures IKEv2 can be used for Opportunistic Security (also known as Opportunsitic Encryption) to defend against Pervasive Monitoring attacks without the need to sacrifice anonimity.},
}