Abstract: Although the Optimal Parity Assignment（OPA） steganography has the characteristics of good concealment and small distortion，it will be revealed for it’s generated binary image，which color is confused.This paper proposes an improved OPA steganography method，which introduces the color intensity into the color sets of the OPA to optimize the color parity assignment.The new method can eliminate the effect of the confused color in the generated binary image，and keep the high stego-data quotiety at the same time.SHA-1 algorithm is also introduced to implement the new stego-data algorithm，which improves the security of the new method.

摘要： 最佳奇偶分配密写（OPA）是针对调色板图像密写中的一种低失真、高隐蔽性的方法。首先对OPA算法及其分析算法进行了深入研究。并针对颜色混乱分析提出了一种新型OPA算法，该算法引入亮度分量参与颜色的奇偶分配，能够有效兼顾密写信息容量和信息安全的双方面要求。最后，还提出利用SHA-1算法完成新密写算法的伪随机游走写入，进一步提高了密写过程的安全性和隐蔽性。