How to Install the Openssl Libraries on Ubuntu

How do I install the OpenSSL libraries on Ubuntu?

You want to install the development package, which is libssl-dev:

sudo apt-get install libssl-dev

Why 'apt-get install openssl' did not install last version of OpenSSL?

You should choose the version you want to install on the OpenSSL's site. It seems you want to install the 1.1.0.
So, do as it follows.

wget https://www.openssl.org/source/openssl-1.1.0f.tar.gz
tar xzvf openssl-1.1.0f.tar.gz
cd openssl-1.1.0f
./config -Wl,--enable-new-dtags,-rpath,'$(LIBRPATH)'
make
sudo make install

openssl version -a

It is done. It is as simple as that.
Good luck with it.

I am trying to install openssl package in R using Ubuntu 18.04 without success

Try in terminal:

sudo apt-get install libssl-dev

and after that try to install package openssl in R again.

How do I install and build against OpenSSL 1.0.0 on Ubuntu?

Get the 1.0.0a source from here.

# tar -xf openssl-1.0.0a.tar.gz
# cd openssl-1.0.0a
# ./config
# sudo make install

This puts it in /usr/local/ssl by default

When you build, you need to tell gcc to look for the headers in /usr/local/ssl/include and link with libs in /usr/local/ssl/lib. You can specify this by doing something like:

gcc test.c -o test -I/usr/local/ssl/include -L/usr/local/ssl/lib -lssl -lcrypto

EDIT DO NOT overwrite any system libraries. It's best to keep new libs in /usr/local. Overwriting Ubuntu defaults can be hazardous to your health and break your system.

Additionally, I was wrong about the paths as I just tried this in Ubuntu 10.04 VM. Fixed.

Note, there is no need to change LD_LIBRARY_PATH since the openssl libs you link against by default are static libs (at least by default - there might be a way to configure them as dynamic libs in the ./config step)

You may need to link against libcrypto because you are using some calls that are built and defined in the libcrypto package. Openssl 1.0.0 actually builds two libraries, libcrypto and libssl.

EDIT 2 Added -lcrypto to gcc line.

Unable to locate package openssl-dev

openssl-dev is for RedHat and CentOS systems.

Install openssl and libssl-dev instead, which works on Ubuntu and Debian.

sudo apt-get install openssl libssl-dev