java - CipherInputStream how to turn on/off the cipher for different bytes you are reading -

i trying read file has data encrypted , not encrypted.
start of each message has unencrypted header contains byte size of encrypted message follows.

my class read extends fileinputstream , override read operation.
when create stream class, pass in cipher constructor.

in read(), need able turn cipher on/off different bits in file buffer.
is there way turn on/off cipher when performing read?

thank you

as far know, can't this. you'd have split data.