Q:

Why the data in Aircraft's Black Box is Encrypted?

I have read somewhere that the Data in Air Craft Black Boxes are encrypted using various algorithm and only the manufacturers could gain access to the actual data of the BlackBoxe,
Why the data in Aircraft's Black Box is Encrypted anyway ?
Here is the source where i read that: http://www.astm.org/SNEWS/OCTOBER_2001/bbox_oct01.html
For example, after any aircraft crash incident the airline company has to send the Black Box to the original manufacturers of it so that the data could be revived, and It takes month to recover the data.
I am saying that , What is the need to encrypt data at first place ?

A:

First thing: encoding is not the same as encrypting. 
Not all flight recorders are encrypted, it is however a feature requested by some users, e.g. Ministries of Defence. 
Keep in mind that flight recorders are not solely for crash investigations and can be read out and analyzed at any time. As flight recorders include conversations on communication channels it can be useful to encrypt this data. 

