用 openssl 生成一对私钥和公钥

参考网站：

http://www.madboa.com/geek/openssl/

go to the folder in terminal.

1.  openssl genrsa -out mykey.pem 1024

2.openssl rsa -in mykey.pem -pubout > mykey.pub  extract the public key and print that out.

This is what happen in terminal:

lin-wangs-MacBook-Pro:key linwang$ openssl genrsa -out private.pem 1024
Generating RSA private key, 1024 bit long modulus
........++++++
............++++++
e is 65537 (0x10001)
lin-wangs-MacBook-Pro:key linwang$ openssl rsa -in private.pem -pubout > public.pub
writing RSA key