Images (typically JPEG) are used as evidence against cyber perpetrators. Typically the file is carved using standard patterns. Many concentrate on carving JPEG files and overlook the important of thumbnail in assistin...Images (typically JPEG) are used as evidence against cyber perpetrators. Typically the file is carved using standard patterns. Many concentrate on carving JPEG files and overlook the important of thumbnail in assisting forensic investigation. However, a new unique pattern is used to detect thumbnail/s and embedded JPEG file. This paper is to introduce a tool call PattrecCarv to recognize thumbnail/s or embedded JPEG files using unique hex patterns (UHP). A tool called PattrecCarv is developed to automatically carve thumbnail/s and embedded JPEG files using DFRWS 2006 and DFRWS 2007 datasets. The tool successfully recovers 11.5% more thumbnails and embedded JPEG files than PredClus.展开更多
文摘Images (typically JPEG) are used as evidence against cyber perpetrators. Typically the file is carved using standard patterns. Many concentrate on carving JPEG files and overlook the important of thumbnail in assisting forensic investigation. However, a new unique pattern is used to detect thumbnail/s and embedded JPEG file. This paper is to introduce a tool call PattrecCarv to recognize thumbnail/s or embedded JPEG files using unique hex patterns (UHP). A tool called PattrecCarv is developed to automatically carve thumbnail/s and embedded JPEG files using DFRWS 2006 and DFRWS 2007 datasets. The tool successfully recovers 11.5% more thumbnails and embedded JPEG files than PredClus.
文摘目的随着云存储服务的普及,人们越来越习惯在云中存储图像,但存在高开销的数据传输、数据篡改以及可能泄露用户隐私的问题。为此,本文提出一种新型的基于2维压缩感知(2D compressed sensing,2DCS)与缩略图格式保留加密(thumbnail-preserving encryption,TPE)结合的数据隐私保护方案。方法利用确定性二进制对角(deterministic binary block diagonal,DBBD)矩阵作为测量矩阵对原始图像进行压缩采样,压缩采样的观测值能够保留图像的结构相似性,提高视觉上的观感体验,并通过误差像素集和显著性像素集生成关键像素集,利用2维离散小波变换将关键像素集嵌入压缩信号,在保证图像恢复质量的同时极大地去除冗余信息。最后通过TPE使合法用户在隐私性与可用性之间取得良好平衡。结果该方案能够在压缩图像的同时保留图像的形态和重要特征,在压缩图像以降低存储成本的同时保证图像边缘和纹理等重要部分的重建质量。实验结果表明,重建图像的视觉效果与原图非常接近,实测平均信噪比(peak signal to noise ratio,PSNR)和结构相似性(structural similarity,SSIM)显著提升。压缩率为0.25时,平均PSNR大于31.8 d B,SSIM大于0.97。相比于未使用关键像素集重建图像,PSNR和SSIM分别提高约4%用于实际的图像云存储服务。结论与传统的压缩加密方案相比,基于2DCS与TPE的隐私保护方案(2DCS-TPE)不仅保证隐私性、可用性及合法用户体验,还实现了低采样复杂度和节约资源存储成本,减轻设备负担,并且具有较好的重建质量。
