Secret Communication Based on Quantization

• Main Authors: Wei-Chih Chen, 陳韋志
• Other Authors: Po-Yueh Chen
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/73836304313770864536

碩士 === 國立彰化師範大學 === 資訊工程學系 === 100 === 　　Because of the prevalence of internet, the information security issues have attracted much attention in recent years. Protecting privacy of exchanging information through media becomes the subject of many studies. Cryptography effectively provides protection for the privacy of both senders and receivers. On the other hand, steganography is also widely used to increase more protection mechanism. JPEG, the most common format of storage and transformation for natural images, is a general standard for still image coding. The quantization of JPEG is to quantize the coefficients transformed by Discrete Cosine Transform (DCT) using the Quantization Table (QT) generated by a quality factor. Quantizing DCT coefficients by different QTs can be adopted to record the secret messages. Based on the variation of QTs, we propose two schemes in frequency domain to improve a data hiding method, in terms of correct extraction rate and image quality. Based on the same concept, we propose another scheme in spatial domain which effectively increases the embedding capacity. Experimental results show that the proposed approaches can provide better correct extraction rate, higher image quality, and satisfactory embedding capacity.