Double Jpeg detection with the same quantization matrix (Notes)

1. Introduction

介绍一下几篇论文中等质量双压缩检测的方法,备忘。State of the-art double jepg compression detection with the same quantization matrix.

2. Methods

2.1 Proposed by Fangjun et al.

Detecting Double JPEG Compression With the Same Quantization Matrix

2.1.1 jpeg压缩和解压缩过程导致的三种误差

i. 量化误差 压缩过程中,DCT系数量化导致的误差
ii. 截断误差 解压缩过程中,IDCT变换可能导致值在[0,255]之外,需要截断到0或者255
iii. 舍入误差 解压缩, IDCT变换得到的值为浮点数,需要舍入为最接近的整数

2.1.2 jpeg多重压缩统计特征

\(J_n\)代表压缩n次的Jpeg图片,\(D_n\)代表 \(J_n\)和\(J_{n+1}\)中JPEG系数(量化后的DCT系数)不一样的个数,\(S_n\)代表\(J_n\)中非0 JPEG系数的个数。
统计特征:随着n增加,\(D_n\)单调减小

Read more   2016/7/31 posted in  Digital Image Forensics

Digital image forensics: a booklet for beginners

1. Introduction

  • Digital image forensics(DIF)
    • two principal research paths:
      1. attempt at answering question a)(device captured the image as declared), by performing some kind of ballistic analysis to identify the device that captured the image, or at least to determine which devices did not capture it.
      2. exposing traces of semantic manipulation (i.e. forgeries) by studying inconsistencies in natural image statistics.

2. the role of digital image forensics in multimedia security

  • acquisition process and the tampering techniques leave subtle traces

    • active protection: watermarking

    - passive protection: tools in digital image forensics

Read more   2016/7/31 posted in  Digital Image Forensics