openssl实例。
环境：ubuntu 16.04 64 bit。

一、安装

sudo apt-get install libssl-dev openssl

二、生成证书

sudo openssl genrsa -out privkey.pem 2048

genrsa表示生成rsa密钥，-out指定输出文件为privkey.pem，最后的2048是私钥大小，这里用默认值2048。

$ sudo openssl req -new -x509 -key privkey.pem -out cacert.pem -days 1024

req -new表示生成一个新证书请求，-key指定用到的私钥文件（即上面已经生成的privkey.pem），-out指定证书文件为cacert.pem，-days表示证书有效期，单位为天数，默认是365，这里改为1024。

执行过程如下，其中“:”为手动输入信息，也可直接回车：

You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:CN
State or Province Name (full name) [Some-State]:Guangxi
Locality Name (eg, city) []:nanning
Organization Name (eg, company) [Internet Widgits Pty Ltd]:CST Studio
Organizational Unit Name (eg, section) []:CST
Common Name (e.g. server FQDN or YOUR name) []:Late Lee
Email Address []:li@latelee.org

三、代码

待写