How to hide password from the expdp/impdp

 Hello All,

I am tried to hide the password during datapump export / import at Oracle 10g version. Haved tried to make use of parfile, however, this is a plain text. Can it be possible to use mkfifo to make use the pipe cos having following error. Seemed that the data pump can not get the input from the mkfifo pipe :

>nohup echo "USERID=username/password DIRECTORY=d_app_MAPT DUMPFILE=isb_crr_ext_201101.dmp LOGFILE=d_app_MAPT_LOG:Exp_isb_crr_ext_20110104.log TABLES=TBL_MAPT_ISB_CRR_ext EXCLUDE=INDEX" > test.par &

[1]     2044102
>nohup expdp parfile=test.par &

[3]     2166938
>Sending nohup output to nohup.out.