ORA-19913: unable to decrypt backup

admin

ORA-19913: unable todecrypt backup
Cause: A backup piece could not be decrypted. This message isaccompanied
with another message that indicates the name of the encrypted backup that could
not be restored. The reason could be either that an invalid password wasentered,
or that, when using transparent decryption, the database external securitydevice
is not open.
Action: Ifpassword-based restore was enabled for this backup, then supply the
correct password using the RMAN SET DECRYPTION command. If transparent
restore was enabled for this backup, then ensure that the database external
security device is open.