中文摘要：

提出了一种在数字印章图像中的圆环上嵌入信息的方法,以实现文档认证的目的。分析了Bresenham圆序列的各种性质,提出了两个具体的圆环信息嵌入算法,分析了它们的嵌入量和平均形变量。第一个算法仅在圆环的外圆中嵌入数据,其形变较小;第二个算法同时在外圆和内圆中嵌入信息,使信息嵌入量增大了一倍。实验与分析表明,两种算法的平均形变量均小于1像素,其嵌入效果也令人满意。此外,两种算法在普通大小的数字印章中可分别嵌入HMAC-SHA512认证码和1024比特的RSA签名结果。

英文摘要：

This paper presents a method to embed information in digital image of seal for the purpose of document authentication.The properties of sequences generated by Bresenham circle-drawing algorithm are investigated.Two algorithms to embed information in rings of seal image are proposed and their embedding capacity and distortion are analysed.The first one embeds data in outer circle of the ring and has a smaller distortion;the second one embeds data in inner and outer circles of the ring whose embedding capacity is double as that of the first algorithm.The distortion of two algorithms is satisfactory for common users and both of them have average distortion of less than 1 pixel.Moreover,a seal image with common size can accommodate the outputs of HMAC-SHA512 and RSA digital signature by two algorithms.