OpenSSL是一个开源项目，包括密码库和SSL/TLS工具集。 从项目的官方站点可以看到：
OpenSSL项目是安全套接字层（ secure sockets layer， SSL）和传输层安全（ transport layer security， TLS）协议的一个实现，是大家共同努力开发出的代码可靠、功能齐全、商业级别的开源工具集。项目由遍布世界的志愿者所组成的社区进行管理，他们通过互联网进行沟通、计划和开发OpenSSL工具集以及相关的文档。
OpenSSL在这一领域已经成为事实上的标准，并且拥有比较长的历史。现在几乎所有的服务器软件和很多客户端软件都在使用OpenSSL，其中基于命令行的工具是进行密钥、证书管理以及测试最常用到的软件了。
确定 OpenSSL 版本和配置
查看ubuntu版本
查看OpenSSL版本
上面最后一行的输出（ /usr/lib/ssl）是OpenSSL默认情况下查找配置和证书的目录 。
misc/目录包含一些补充脚本，其中最有用的脚本允许你实现一个私有的证书颁发机构。
查看可用命令
第一部分标准命令Standard commands列出了所有可以使用的工具。如果对于某个命令，想获取更加详细的信息，可以使用man加上工具的名称。例如man ciphers会告诉我们密码套件是如何配置的。
第二部分消息摘要命令Message Digest commands展示了可用的消息摘要命令。
第三部分加密命令Cipher commands 展示了所有的加密命令 。
创建可信证书库
OpenSSL没有自带可信根证书（也叫作可信证书库），所以如果你是自己从头开始安装的话，那么就需要从别的地方找找了。一种选择是使用操作系统自带的可信证书库，一般来说没有问题，但是这个可信证书库可能不是最新的。更好的一种选择是从Mozilla那里获取，虽然麻烦一点 。
密钥和证书管理
多数用户借助OpenSSL是因为希望配置并运行能够支持SSL的Web服务器。整个过程包括3个步骤： (1) 生成强加密的私钥； (2) 创建证书签名申请（ certificate signing request， CSR）并且发送给CA； (3) 在你的Web服务器上安装CA提供的证书。
生成密钥
现在，一般认为2048位的RSA密钥是安全的，所以你应该采用这个长度的密钥。 DSA密钥也应该不少于2048位， ECDSA密钥则应该是256位以上。
使用genrsa命令来生成RSA密钥
openssl genrsa -aes128 -out fd.key 2048
这里，我指定私钥会使用AES-128算法来加密保存。
私钥以所谓的PEM格式存储，该格式仅包含文本：
cat fd.key
乍一看私钥是一堆随机数据，其实不是。你可以使用下面的rsa命令解析出私钥的结构：
openssl rsa -text -in fd.key
Private-Key: (2048 bit)
modulus:
00:b3:02:c2:68:7a:bd:b3:11:47:98:d9:25:e1:21:
d8:16:84:aa:e7:23:85:aa:f9:38:8f:e2:7f:d1:b5:
2f:76:c8:5a:d9:75:f9:6c:d2:54:dd:e0:b2:be:3c:
f6:eb:9b:0e:3d:b6:37:eb:02:d1:44:09:09:40:f8:
4d:5d:1d:41:1d:53:79:dc:b1:55:2e:e7:8b:0a:62:
b7:07:2e:55:ef:fc:92:96:6a:ef:3c:27:0a:74:17:
8e:57:b7:79:d5:83:5f:cc:53:a9:e6:b9:8a:fa:00:
23:b9:ec:78:e2:a3:69:81:ac:28:3e:06:cb:92:05:
db:35:7b:00:b3:fc:52:da:2a:17:1c:14:67:67:ad:
1f:d4:e2:80:51:9f:40:4c:b8:a7:3e:9a:8b:2e:f8:
5c:a7:dd:73:55:84:c7:4d:9b:eb:24:0a:c7:b6:b0:
57:fc:96:a2:9a:81:14:18:dc:20:db:8b:d1:31:e1:
5d:01:78:23:cb:20:1d:c2:a4:fc:bd:da:b2:16:fc:
63:22:b9:31:d1:50:21:78:07:b6:91:9e:47:10:de:
80:3d:d4:8e:bb:cb:d0:ca:ba:8e:7b:6d:ba:3c:b5:
9a:af:49:96:8a:6f:72:bc:cc:a8:73:07:1f:8e:d3:
77:99:98:72:9e:35:eb:01:70:ee:f5:75:33:e9:ff:
e3:e5
publicExponent: 65537 (0x10001)
privateExponent:
7b:17:b5:a8:f4:65:c7:61:65:73:34:36:78:e5:b5:
da:5e:25:ca:c4:c1:60:7c:f9:28:ef:9d:e7:0d:08:
f3:4b:f8:34:ba:8b:e6:09:87:b3:fe:93:ca:7e:cf:
67:d9:7a:64:73:0d:66:7b:cc:7c:55:1e:58:df:a5:
0b:17:57:b4:1b:b7:9b:4b:11:81:2c:54:8e:b2:ac:
9a:b2:81:03:82:11:26:7f:a7:bc:1c:38:72:f5:d3:
ba:7b:7e:ba:94:18:e6:be:cd:00:cb:ab:46:17:9c:
79:77:a2:f4:6d:5b:da:80:10:37:fe:a2:32:e9:f5:
ff:83:72:4b:51:81:83:63:f1:89:7b:7e:80:35:5e:
55:92:8e:11:8c:bb:d8:36:b8:34:02:6d:ed:14:e0:
09:1a:d2:ea:90:d3:b8:04:cc:c3:48:1d:10:30:39:
da:e2:ab:a9:f5:a8:83:3b:54:6e:1f:8e:2d:6a:7e:
5b:2c:ef:0f:6b:b2:d9:33:d1:68:f7:b7:7b:ca:8f:
bf:33:f6:77:0d:88:f9:18:db:cc:be:16:93:d0:92:
be:8a:22:8c:aa:da:fa:80:59:eb:69:85:d3:ff:de:
c1:58:fd:5b:92:37:21:56:eb:56:ad:c4:d0:dd:96:
cd:55:e6:97:ed:e4:15:fb:10:de:a3:8e:75:0e:c7:
2d
prime1:
00:d9:48:10:0b:85:a5:bb:98:ef:03:89:05:37:74:
9a:97:2b:00:cf:6e:3a:bd:a2:8e:b0:a4:e9:de:32:
72:14:a8:50:4d:de:b7:d1:fa:bc:3c:43:97:c6:fe:
d2:24:a2:da:56:ff:40:be:75:bf:ee:63:bf:04:50:
dc:d3:8d:ea:31:77:11:f8:b1:48:55:39:c5:f1:92:
46:df:34:68:47:8f:70:3d:72:5c:b8:a7:3d:31:14:
44:38:f5:ff:2d:38:78:08:34:d0:2b:80:8b:63:fb:
bc:40:e1:29:91:37:99:f4:0b:36:5a:e5:42:19:81:
ec:e0:22:30:8c:8e:38:7c:3f
prime2:
00:d2:e8:dd:6d:e5:e7:62:2c:24:74:fb:c1:e3:52:
d6:f7:78:29:7d:39:03:65:76:d3:57:84:10:78:7f:
b1:08:9d:68:ee:f7:5c:50:d7:51:a0:e5:e8:ca:fc:
7d:2e:18:64:9a:c8:46:89:4d:49:86:5b:73:83:bf:
66:21:ac:45:98:b5:37:ce:6e:1f:ff:c1:5a:f5:2f:
1b:e1:67:75:a3:0f:06:cd:17:24:24:69:90:f5:ed:
2b:c8:b8:9c:be:ab:1f:a8:ba:79:6c:eb:e3:4d:c5:
c3:00:5c:17:6c:1d:de:c4:50:ff:d8:7c:6e:ef:8b:
41:c8:40:08:a7:60:b3:e6:db
exponent1:
00:8c:b1:40:d2:75:23:af:a9:83:7a:c2:8a:82:32:
1a:b7:af:bc:c2:94:19:ad:19:49:53:d0:35:2f:0f:
73:17:35:35:6a:76:c0:88:52:d6:f8:1e:bc:74:ba:
23:d0:5d:33:0c:0a:14:1e:3f:98:9c:00:32:7b:d4:
f0:68:7c:08:1d:27:80:97:8c:13:ce:3b:ae:94:91:
a7:1a:78:90:dd:65:5f:c4:29:fd:28:04:02:77:79:
2c:03:c6:26:09:5d:fb:3b:35:17:66:53:c1:ee:67:
de:aa:14:22:1a:49:ea:82:3f:90:5e:a2:fc:7e:0f:
c7:16:0a:8d:6d:35:da:15:79
exponent2:
00:87:07:3b:2c:ae:f2:32:72:1c:6d:20:f9:82:f6:
78:56:3b:82:24:7f:a9:e2:fd:ee:54:ab:62:78:23:
18:4e:71:a8:ca:c5:67:3f:02:7b:6a:4d:87:7a:dd:
a7:af:29:42:cf:ad:c5:2b:06:66:3a:34:b6:81:f4:
ba:08:78:e8:9d:d9:f7:7e:9c:16:b4:81:30:20:a5:
26:6e:6a:f4:6f:8e:a1:46:10:b8:bc:ef:31:35:a1:
c0:54:63:8d:46:ac:fc:39:e4:18:f5:59:18:4f:a4:
7b:31:f1:c3:b5:1e:72:8e:b1:64:fb:4e:bf:1f:71:
c2:8d:d8:21:32:37:c1:35:dd
coefficient:
00:9a:f0:08:62:0b:0d:0c:d0:ff:23:f1:06:8d:e4:
8f:db:7d:16:f5:33:d5:6c:d1:dc:1e:d1:35:33:a1:
4f:7b:e4:ef:ed:eb:ac:a1:36:a1:87:44:f3:e1:d2:
24:3b:45:c0:d3:47:92:63:ec:ec:06:aa:a4:da:9c:
f4:0b:97:70:26:d1:c1:33:d8:40:ca:b7:46:95:e3:
a3:f6:ed:be:76:bf:1d:ee:71:a8:0f:9e:73:9a:e3:
5c:a1:d4:c3:03:77:29:ea:47:64:a4:e0:ac:4d:c4:
25:ea:cf:4a:15:58:fa:bb:b0:bd:7d:0c:cd:0f:23:
fc:9b:a8:72:fb:29:40:72:a7
writing RSA key
-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----