3.1 installation openSSL

Download the openSSL exe file at slproweb.com/products/Wi… Download the appropriate installation package from the website.

After downloading, open the installation and select the installation location. Do not install 64-bit and 32-bit files in the same directory.

Select copy the DLL to the OpenSSL directory.

After the installation is complete, if you want to donate, you can do so. If you don’t want to donate, uncheck and click “Finish”.

3.2 Setting up an OpenSSL Environment with VS2017

Create a new empty project and configure the project properties (include directories added to openSSL’s include folder; Library directory Add openSSL’s lib folder.

Copy libeay32.dll and ssleay32.dll in the bin folder of the OpenSSL installation directory to the project directory.

3.3 Generating a Certificate

Start by generating the server-side private key (key file)

 
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1. openssl genrsa -des3 -out server.key 1024

This will prompt you for a password that will be used to encrypt the key file (des3 is the encryption algorithm, of course, you can choose any other algorithm that you think is secure). You will need to enter the password whenever you need to read this file (through the command or API provided by OpenSSL). You can remove this password if it’s inconvenient, but be sure to use other protection measures!

Command to remove the key file password:

 
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1. openssl rsa -in server.key -out server.key

 
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1. openssl req -new -key server.key -out server.csr

The Certificate Signing Request (CSR) is generated, and the GENERATED CSR file is submitted to the CA to form the server’s own Certificate. There will be a prompt on the screen, follow its instructions step by step to enter the desired personal information.

Do the same for the client to generate the key and CSR files.

 
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1. openssl genrsa -des3 -out client.key 1024
2. openssl req -new -key client.key -out client.csr

The CA key file is generated to generate a CA self-signed certificate.

First generate the CA key file:

 
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1. openssl genrsa-des3 -out ca.key 1024

Regenerating a CA self-signed certificate:

 
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1. openssl req -new -x509 -key ca.key -out ca.crt

Sign the server. CSR and client. CSR files you just generated with the generated CA certificate.

Openssl also ships with a file called ca.pl that you can use to generate files.

3.4 Programming of server and client

3.4.1 Client programming framework

 
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1. /* Generate an SSL structure */
2. meth = SSLv23_client_method();
3. ctx = SSL_CTX_new (meth);
4. ssl = SSL_new(ctx);
5.  
6. /* The following is the normal socket process */
7. fd = socket();
8. connect();
9.  
10. /* Connect the socket to the SSL structure */
11. SSL_set_fd(ssl,fd);
12.  
13. /*SSL handshake process */
14. SSL_connect(ssl);
15.  
16. / * the SSL_write (), SSL_read () instead of the original the write (), read () * /
17. SSL_write(SSL," I am the client ",strlen(" I am the client "));

3.4.2 Server writing framework

 
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1. /* Generate an SSL structure */
2. meth = SSLv23_server_method();
3. ctx = SSL_CTX_new (meth);
4. ssl = SSL_new(ctx);
5.  
6. /* The following is the normal socket process */
7. fd = socket();
8. bind();
9. listen();
10. accept();
11.  
12. /* Connect the socket to the SSL structure */
13. SSL_set_fd(ssl,fd);
14.  
15. /*SSL handshake process */
16. SSL_connect(ssl);
17.  
18. / * the SSL_write (), SSL_read () instead of the original the write (), read () * /
19. SSL_read (ssl, buf, sizeof(buf));