MD5 加密的实现

#pragma mark - Public Method 获取md5值
+ (NSString *)getMD5:(NSString *)str {
    if (!str)
    {
        return nil;
    }
    const char *cStr = [str UTF8String];
    unsigned char result[16];
    CC_MD5( cStr, strlen(cStr), result );
    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]
             ] lowercaseString];
    
  
}