MD5 加密方法

#import <CommonCrypto/CommonDigest.h> // Need to import for CC_MD5 access

- (NSString *)md5:(NSString *)str{    const char *cStr = [str UTF8String];    unsigned char result[16];    CC_MD5(cStr, strlen(cStr), result); // This is the md5 call    return [NSString stringWithFormat:        @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",        result[0], result[1], result[2], result[3],         result[4], result[5], result[6], result[7],        result[8], result[9], result[10], result[11],        result[12], result[13], result[14], result[15]        ]; }