Data corruption of encrypted partition

Hi team,

I am encrypting my partition using dm-integrity and dm-crypt utility. I
am trying to corrupt my encryted partition using dd command utiltity as
below

/factory/ is a mounted point of encrypted partition
(/dev/mapper/factory-integrity-crypt)

dd if=/security/file.txt of=/factory/file.txt bs=512 seek=8

I am able to see my file.txt content using cat command

I am trying to corrupt the file content by writing to physical layer of
the encrypted partition using below command

dd if=/security/file.txt of=/dev/mmcblk0p5 bs=512 seek=8


/dev/mmcblk0p5 is the physical layer of the encrypted logical layer
(/dev/mapper/factory-integrity-crypt)


When I open the file , the file content is not corrupted and even I can
unmount and mount the partition again even if I corrupt the physical
block device of encrypted partition. Is this behaviour is expected?
Please provide your input.

Regards,
Sharmila