一种频域加密算法，图像经过DCT变换得到DCT系数，然后对DCT系数进行加密。然后对加密的DCT系数进行DCT反变换图像数据。最后对其加密后的图像数据进行线性变换来调整图像数据的取值范围在[0，255]。最后得到加密图像-A frequency-domain encryption algorithm, the image obtained through the DCT transform DCT coefficients, and then encrypt the DCT coefficien

对.tar/.zip/文件进行解密,通过缓冲区调整控制文件解密速度.-Of .tar/.zip/decrypt files, decrypt files by a buffer to adjust the speed control.

md5的C语言实现，百度到的，代码写的不错，自己调整了格式以便于阅读-the implement of the md5 with C language, the code is writed very well, i adjust the format for easier reading