# File lib/openid/association.rb, line 64
    def serialize
      data = {
        :version => '2',
        :handle => handle,
        :secret => Util.to_base64(secret),
        :issued => issued.to_i.to_s,
        :lifetime => lifetime.to_i.to_s,
        :assoc_type => assoc_type,
      }

      Util.assert(data.length == FIELD_ORDER.length)

      pairs = FIELD_ORDER.map{|field| [field.to_s, data[field]]}
      return Util.seq_to_kv(pairs, strict=true)
    end