참고문서: http://www.fis.unipr.it/pub/linux/redhat/9/en/doc/RH-DOCS/rhl-cg-ko-9/s1-secureserver-certs.html
1. private key 생성.
# openssl genrsa -des3 -out server.key 1024
Generating RSA private key, 1024 bit long modulus
……….++++++
………………………….++++++
e is 65537 (0x10001)
Enter pass phrase for server.key:
Verifying – Enter pass phrase for server.key: