The WannaCry System

The wild country

In the May of 2017 when things were standing still, a thing knocked on doors of digital world.
The most popularly running Windows Operating system was about to meet with its nightmare.

A ransomeware that would go on to affect not only the millions of personal computers around the world but also bringing down major organisational work including that of:

• National Health Service hospitals of England and Scotland resulting in postponed surgeries and diverted ambulances
• Motor manufacturing giants like Nissan and Renault halting the production
• Courier giants like Fedex stopping
• Railways in Russia
• Goverment offices and Police Stations in India

Walk before the knock

EternalBlue was an exploit in the Windows saved by National Security Agency (NSA) for future use.
Everyone knows what future use means.

Though Microsoft had already earlier sent a patch, but there were still a majority of systems hanging around that have either not installed the update or were out of vendors support duration or had Windows version that Microsoft had stopped supporting.

This exploit information got stolen by a group of hackers called The Shadow Brokers.

Short period of time later the knock was heard.

Keys

In the world of technology safety and conceiling are handled by keys.
You encrypt the data with your key and the person who is supposed to receive it will decrypt using his own.

There are two types of key-system:

Asymmetric:
This uses two set of keys. One for encryption, another for decryption.
Popular technology in this area being RSA, Diffie-Hellman.
Refer this link for deep-dive in RSA.
Refer this link for deep-dive in Diffie-Hellman.

Symmetric:
This uses only one key for both encryption and decryption.
Popular technology in this area being AES.
Refer this link for deep-dive in to AES.