hide certain field writing in signing up

[okui]

Hi,

 

 

i want to collect some info about the client,

 

some day,he may lose some info and we need to check if this account is his one,

 

we hope they can answer some question,

 

for example,what is your mother' name...etc,

 

and they answer it when signing up,

 

but those info can not show in client area,only admin area can find those info,

 

some day,they may ask some service and we need to verify,

 

we may ask them those question to verify.

 

 

about the hidden field,how can i add it in signing up page?

 

 

thank