PDF Steganography based on Chinese Remainder Theorem

We propose different approaches of PDF files based steganography, essentially based on the Chinese Remainder Theorem. Here, after a cover PDF document has been released from unnecessary characters of ASCII code A0, a secret message is hidden in it using one of the proposed approaches, making it invisible to common PDF readers, and the file is then transmitted through a non-secure communication channel. Where each of our methods, tries to ensure the condition that the number of inserted A0 is less than the number of characters of the secret message s.