balloon-cost {
    {field . {map}}
    {field s {int} >0} {# space cost}
    {field t {int} >0} {# time cost}
    {field p {int} >0} {# parallel cost}
}

kem-balloon-blake2b-hkdf {
    {field . {map}}
    {field a {str} =balloon-blake2b-hkdf}
    {field cek {bin} >0} {# wrapped CEK}
    {field salt {bin} >0}
    {field cost {with balloon-cost}}
}