Transactions on Data Hiding and Multimedia Security V

In forensic investigations, it is common for forensic investigators to obtain a photograph of evidence left at the scene of crimes to aid them catch the culprit(s). Although, fingerprints are the most popular evidence that can be used, scene of crime officers claim that more than 30% of the evidence recovered from crime scenes originate from palms. Usually, palmprints evidence left at crime scenes are partial since very rarely full palmprints are obtained. In particular, partial palmprints do not exhibit a structured shape and often do not contain a reference point that can be used for their alignment to achieve efficient matching. This makes conventional matching methods based on alignment and minutiae pairing, as used in fingerprint recognition, to fail in partial palmprint recognition problems. In this paper a new partial-to-full palmprint recognition based on invariant minutiae descriptors is proposed where the partial palmprint’s minutiae are extracted and considered as the distinctive and discriminating features for each palmprint image. This is achieved by assigning to each minutiae a feature descriptor formed using the values of all the orientation histograms of the minutiae at hand. This allows for the descriptors to be rotation invariant and as such do not require any image alignment at the matching stage. The results obtained show that the proposed technique yields a recognition rate of 99.2%. The solution does give a high confidence to the judicial jury in their deliberations and decision.

For post incident investigation a complete reconstruction of an event is needed based on surveillance footage of the crime scene and surrounding areas. Reconstruction of the whereabouts of the people in the incident requires the ability to follow persons within a camera’s field-of-view (tracking) and between different cameras (tracing). In constrained situations a combination of shape and color information is shown to be best at discriminating between persons. In this paper we focus on person tracing between uncalibrated cameras with non-overlapping field-of-view. In these situations standard image matching techniques perform badly due to large, uncontrolled variations in viewpoint, light source, background and shading. We show that in these unconstrained real-life situations, tracing results are very dependent on the appearance of the subject.

This paper provides a review of previous work and recent results on the design and analysis of collusion-resistant fingerprinting systems. Collusion attacks examined in previous work are with constant weights for all colluders. Collusion attacks on continuous media (such as audio and video) with time-varying weights are simple to implement, but have never been treated by other researchers. In recent years, we have proposed a new fingerprinting system called MC-CDMA-based fingerprinting since it is inspired by the multi-carrier code division multi-access (MC-CDMA) communication technique. The time-varying collusion attack can be conveniently analyzed by drawing an analogy to the multi-access interference (MAI) problem in a wireless communication system with a time-varying channel response. As a result, many powerful tools from wireless communications can be borrowed to design a collusion-resistant fingerprinting system. They include codeword design, shifted spreading, pilot-based channel estimation, receiver design, etc. Furthermore, we present results on capacity, throughput, and distortion of a colluded media file. Finally, we will mention some open research problems.

We herein propose an image matching in the scrambled domain for preventing illegal image matching, which is defined as a malicious and intentional act conducted in order to deduce the content of images. The phase of discrete Fourier transform (DFT) coefficients of images is scrambled for visual protection. In addition, the magnitude of DFT coefficients is scrambled for preventing illegal image matching. Phase-only correlation (POC) or phase correlation can be applied directly to images in the scrambled domain for alignment and similarity. The accuracy of POC in the scrambled domain is the same as that in the non-scrambled domain. Simulations are presented to confirm the appropriateness and effectiveness of the proposed scrambling.

Visual cryptography (VC) is a powerful technique that combines the notions of perfect ciphers and secret sharing in cryptography with that of raster graphics. VC takes a binary image (the secret) and divides it into two or more pieces known as shares. When the shares are printed on transparencies and then superimposed, the secret can be recovered. No computer participation is required, thus demonstrating one of the distinguishing features of VC. VC is a unique technique in the sense that the encrypted message can be decrypted directly by the human visual system (HVS). In this survey, we will summarize the latest developments of visual cryptography since its inception in 1994, introduce the main research topics in this area and outline the current problems and possible solutions. Directions and trends for future VC work shall also be examined along with possible VC applications.

Visual cryptography provides a very powerful technique by which one secret can be distributed into two or more pieces known as shares. When the shares are printed on transparencies and then superimposed exactly together, the original secret can be recovered without computer participation. In this paper, we take multiple secrets into consideration and generate a key share for all the secrets; correspondingly, we share each secret using this key share. The secrets are recovered when the key is superimposed on the combined share in different locations using the proposed scheme. Also discussed and illustrated within this paper is how to embed a share of visual cryptography into halftone and colour images. The remaining share is used as a key share in order to perform the decryption. It is also worth noting that no information regarding the secrets is leaked in any of our proposed schemes. We provide the corresponding results in this paper.