How to install cryptography on ubuntu?

The answer is on the docs of cryptography's installation section which pretty much reflects Angelos' answer:

Quoting it:

For Debian and Ubuntu, the following command will ensure that the required dependencies are installed:

$ sudo apt-get install build-essential libssl-dev libffi-dev python-dev

For Fedora and RHEL-derivatives, the following command will ensure that the required dependencies are installed:

$ sudo yum install gcc libffi-devel python-devel openssl-devel

You should now be able to build and install cryptography with the usual

$ pip install cryptography

If you're using Python 3, please use python3-dev instead of python-dev in the first command. (thanks to @chasmani)

If you're installing this on Ubuntu 18.04, please use libssl1.0 instead of libssl-dev in the first command. (thanks to @pobe)

I had the same problem when pip installing the cryptography module on Ubuntu 14.04. I solved it by installing libffi-dev:

apt-get install -y libffi-dev

Then I got the following error:

build/temp.linux-x86_64-3.4/_openssl.c:431:25: fatal error: openssl/aes.h: No such file or directory #include <openssl/aes.h>                         ^compilation terminated.error: command 'x86_64-linux-gnu-gcc' failed with exit status 1

Which I resolved by installing libssl-dev:

apt-get install -y libssl-dev

Installing libssl-dev and python-dev was enough for me on ubuntu 16.04.