**1.2 Digital recording identification features**

Easy bit-to-bit copying process of digital information and inapplicability of traditional "original vs copy" division both with non availability of automated procedures of digital sourcing had led to wide distribution of counterfeit production. Identification based on format features, metadata fields, etc is unreliable because of its removal and forgery simplicity. Use of digital watermarks for content protection is not always possible due to computational complexity of embedding procedure.

Digital Camera Identification Based on Original Images 301

them. DW, as a rule, contain some authentic code, the information on the proprietor or the operating information for reproduction and copying tools. Unlike usual watermarks, DW can be not only visible, but also (as a rule) invisible because by the nature DW are distortions of a signal, which is intended for perception by the person in the first place, and, hence, for preservation of consumer qualities of protected audiovisual production should be as less as possible. Invisible DW are analyzed by the special decoder which renders the decision on their presence, and if necessary, extracts the hidden message. The most suitable objects of protection by means of DW are static images, files of audio- and the video data[1- 3]. DW applications are not limited to information security applications. The basis areas of

Definition of the received information authenticity, plays a special role in a modern information exchange. Usually the digital signature is used for authentication. However it is not quite appropriate for authentication of multimedia information. The message with attached digital signature should be stored and transferred absolutely precisely, «bit-to-bit», while multimedia information can slightly be changed both at storage (at the expense of compression and due to insufficient correcting ability of a code), and at transfer (influence of single or package errors in a communication channel). Thus its quality remains admissible for the user, but the digital signature will not work, so the addressee cannot distinguish true, though and a little changed message from the completely false one. Besides, the multimedia data can be transformed from one format to another, thus traditional means of

It is possible to tell that DW are capable to protect the content of digital audio/video, instead of its digital representation in the form of sequence of bits. An essential lack of the digital signature is also that it is easy to completely remove it from the message and attach the new signature. Signature removal will allow the infringer to refuse authorship or to mislead the lawful addressee concerning authorship of the message. Modern systems of DW are projected so that to minimise possibility of similar infringements without simultaneous essential deterioration of record. DW should be robust or fragile (depending on application) to deliberate and casual influences. If DW is used for authenticity acknowledgement, inadmissible change of the container should lead to DW destruction (fragile DW). If DW contains an identification code, a firm logo, etc. it should remain at the maximum distortions of the container, of course, not leading to essential distortions of an initial signal. Thus, at use DW the basic problem are the attacks, which aim is infringement of their integrity. It is possible to distinguish the following attacks: the attacks directed on DW removal, the geometrical attacks directed on distortion of the container, cryptographic attacks, attacks against the used embedding method and DW checking procedure [4-6]. Researching new methods of embedding DW, robust against malicious attacks is base problem in researching new methods of protection of the multimedia information presented in a digital form. Along with clear advantages of a digital watermarks embedding, its application demands inclusion of the additional block of embedding in structure of each recording device. For already existing modern mobile digital recording devices it leads to at least updating of the microprogram and it can be impossible if computing resources of the device are limited.

DW technology can be united in four groups:


definition of integrity also will not work.



Widening of digital audio and videorecording devices distribution and an abrupt increase of storage density had led to situation where the most frequently identification case is identifiable records that are external to identifiable device, leading to complete absence of the primary physical state of the primary "source" and file system properties. Than the rest identification way are the identification based on file format features and identification based on features of recording path and postprocessing.

Copyright protection task operates with the same features, but the signal can be presented after multiple format conversions, which preserve consumption quality but changes the physical representation of original signal, so the identifiable and applicable features are ones containing in digital *content* rather than *format* representation.

Currently questions of identification of analog audio, still images and video recording devices are well researched and are based on traces which the recording device leaves on the carrier in process of writing at change of its physical properties. It is widely used at any carrying out of the expertizes which example is, in particular, phototechnical examination. Phototechnical expert appraisal represents judicial expertize on research of facsimiles of various property and the content, photos (including numeral), paper pictures (photo), for definite purposes of criminal, civil or arbitration legal proceedings. Each picture contains information about the circumstances concerning procedure of manufacturing. Phototechnical expert appraisal is produced with a view of identification of objects by their images photos, photographic materials and laboratory accessories on traces on negatives and positives, ascertainment of type and mark of "unknown" photofilms, detections on photos traces of tampering , ascertainment of other circumstances linked to photographing and handling of photographic materials (photos, photographic paper).

Thus, phototechnical expert appraisal tasks are subdivided on:

