Image sharing with steganography and authentication

More and more data are being transmitted via the public access network, the Internet, due to its favorable characteristics such as low cost, speed, and reliability. Although the Internet is a public access network, certain data require secrecy, such as commercial or military images, to protect them from illegitimate users during transmission. Steganography is a technique for transmitting secret data without being noticed. This technique hides secret messages into cover media to avoid malicious attacks. The cover media can be digital images, digital videos, source codes, or even Hyper Text Markup Language (HTML) codes. The digital image used to embed the secret data is called a cover image, which becomes a stego-image once the secret data are embedded. With steganography, malicious attackers do not know that a stego-image carries secret data. Therefore, they will not try to extract the data or otherwise trespass on it. However, there is a weakness common to all steganographic techniques. If one of the stego-media is lost or corrupted, the secret data cannot be revealed exactly and completely. Therefore, several secret sharing techniques have been proposed to overcome this weakness. With regard to the concept of secret sharing, the well-known (k, n)-threshold schemes pioneered by Shamir [20] and Blakley [2], respectively, have four characteristics in common: (1) k ≤ n. (2) The secret is shared among n participants. (3) Only k or more participants can reconstruct the original secret. (4) When the number of participants is (k - 1) or less, they cannot recover the original secret.