在程序中由playfair(char *s,int length) 的实现加密和解密；解密原理与加密类似，只是加密过程的逆过程，它基于密文，采用同行取左边，同列取下边，其余取交叉的相反原理；在程序中用FLAG标识区别，当其值为1时，为加密过程；值为0时，为解密过程。-in the proceedings by PLAYFAIR (char * s, int length) the realization of encryption and decryption; encryption and decryption principle similar encryption process is the inverse process. It is based on the secret-using counterparts from the left, with the top candidate out from the rest of the cross from the opposite principle; the identification procedures used FLAG distinction, when its value to 1:00 for encryption process; the value of 0, for decryption.