网络多媒体教学datahidinginimagesjnu.ppt

Outlines Cryptography for Image Protection Digital Image Watermarking Cryptography Cryptography : focuses on methods to make encrypted information meaningless to unauthorized parties A legal user can decode the data with a private key Illegal one can not decrypt the information since the key is secret Symmetric cryptography (Traditional Protection Methods) Drawback of encryption: decrypted media data becomes unprotected Unauthorized Use ofDigital Contents Digital multimedia can be stored, copied, and distributed easily, rapidly, and with no loss of fidelity can be manipulated and edited easily and inexpensively Are these properties always advantageous? Some Hollywood studios will not release DVDs unless copyright protection can be guaranteed USA Today, Jan. 2000:Estimated lost revenue from digital audio piracy US 8,500,000,000.00 Watermarking “A secret message” inserted into unprotected data for ownership proof Inserted message: Watermark Unprotected data: Cover data or host data, such as image, audio clip, video, text, etc. Visible Watermark Claim the ownership and prevent content piracy Robust, Visible but Non-obtrusive Suitable for e.g. live TV broadcast Invisible Watermarkleast significant bit Watermarking model Principle: insert information that travels with the protected data, wherever it goes Watermarking before Encryption Watermark Robustness Watermarking applications Watermarking may be appropriate for applications in which data about a work must be imperceptibly embedded. Different applications place different requirements on watermarking system properties. List of examples discussed Broadcast Monitoring Owner Identification Proof of Ownership Content Authentication Copy Control Broadcast monitoring Broadcast monitoring Verify advertising broadcasts (1997 scandal in Japan) Verify royalty payments ($1000 of unpaid royalties to actors per hour of broadcast) Catch instances of piracy Owner identification Owner identification Help honest people ide