for rbd, how to use qmp directly to add dick

["longguang.yue" <libvirt@xxxxxxx>]

Hi, all:
    in my case, i need to add device via qmp.  but for rbd  drive needs a secret object.  how to produce secret object.  
  'base64 -d'  outputs unreadable code .


-object
secret,id=virtio-disk0-secret0,data=2YVH6svMZa42RfVx8MbIIVjtU6iGO8QzFADuDnLk7BU=,keyid=masterKey0,iv=/m3QyHQ33NeMEfDDMuDEeg==,format=base64


thanks