Encryption key plays central role in detection process of video watermarks, especially in pirated videos

The success of the internet, its increasing penetration, and the quality of service for networks have made the creation, replication, transmission, and distribution of digital video content almost effortless. There is, therefore, a need to protect digital content and enforce intellectual property rights. While DRM protected content is safe during transmission, there is an evident risk of content piracy once content reaches the user device. Hence, watermarking techniques are necessary to protect the content from illegal distribution and identify the exact source of leakage.

Watermarking approaches require embedding watermarks with information and extracting the information in the event of content infringement. The embedded information can be restricted or unrestricted depending on the use case. For example, if copy protection is the primary goal of using a video watermarking technology, the watermark should be readable by everyone and unrestricted key watermarking technology will, therefore, be used. However, if the security of the embedded information is of primary concern, restricted-key watermarking techniques are applied. The usage of cryptographic techniques are, thus, prominent in addressing different security levels required for video protection. Encryption helps in reaping the combined benefits of data hiding and cryptographic techniques. It makes watermark detection significantly more difficult and prevents pirates from tampering with it.

The secret key could include identification information for the authentication of source, a set of codes or parameters of the original un-watermarked content which makes detection more robust since a different key is needed for each watermarked copy. Knowledge of this secret key is needed to embed the watermark as well as detect it. While potential attackers generally do not have access to watermark detecting techniques, a security threat could emerge if they somehow get access to them.

In a secret key scheme, the same key is used for both watermark insertion and extraction. Hence, the key must be transmitted from the owner to the viewer through a secure channel. In case of public keys, the integrity and ownership of the asset can be verified using a public key. In such a system, the owner of the image inserts a watermark using a private key. During the watermark extraction procedure, any person can use the public key to extract a binary watermark that will indicate any changes made to the watermarked file.