Digital signature value /Contents attribute

Hello,

I am currently working on adobe pdf digital signature. I used the DLI sample contained in Adobe PDF library.

During signature calculation, encryptBuffer function (which encrypts the document hash using private key) returns

a 256 characters long hex value which is supposed to be written in /Contents dictionary item under digital signature value object.

But when I inspect the value written inside /Contents in pdf document, it is 262 character long instead of 256. There are 6 additional

hex characters at the start. Can you please explain what do they represent? I have gone through all the documentation available but

couldn't find the answer. DLI doesn't suite us. We are trying to implement signature support by writing signature objects directly in pdf file without using

any Adobe API's. For that purpose we need clarification on those additional 6 characters written in /Contents. Your immediate response will be highly appreciated.