Cryptography

Episode #8 of the course Cyber security basics by FutureLearn

Encryption is a modern form of cryptography that allows us to hide information from others to keep prying eyes out. While it might seem modern, examples of cryptography can in fact be traced throughout history, from the simple ciphers used by Julius Caesar to send military orders to his generals to the famous Enigma codes used in World War II. Modern-day encryption lies at the very heart of cyber security today, and we use this technology in everyday life when ordering online, logging into online banking, using wireless networks, casting electronic votes, withdrawing money from cash machines, and more.

Encryption uses a complex algorithm called a “cipher,” which transforms regular plain text data that is readable by anyone into a series of seemingly random characters called “ciphertext.” To read ciphertext, a special key is needed to decrypt the characters—and only those who possess the correct key can decrypt the data to view the original plain text. There are several types of encryption schemes, but regardless of the type of encryption, the data is only as secure as the passphrase that protects the encryption key.

Most web pages pass simply as plain text across the internet, readable by anyone should they choose to intercept. While the whole of the internet could be protected using cryptography, it takes computer processing power to encrypt and decrypt information, so it is typically reserved for sensitive data. Pages such as news websites or photo galleries are fine as plain text since they don’t contain sensitive content, whereas pages that contain passwords and personal information are pages vulnerable to interception from cybercriminals and as such require strong encryption.

Some websites you visit will be encrypted, and internet banking and online shopping services routinely use encryption to ensure that the data sent to and from your computer is safe from eavesdroppers. Web browsers have made it easy to determine if a website is secure by making all secure addresses begin with https:// rather than http://, with the “s” standing for “secure.” You might also spot a closed padlock symbol in or near the top of your browser window, which shows that a site is secure.

In some cases, web applications use encryption selectively for certain tasks, such as processing online shopping payments or in personal “My Account” areas of sites, which typically contain personal information about users and require a login. We can also choose to use encryption for other purposes, such as sending encrypted emails, though currently these tools are often quite tricky to set up and so aren’t in wide public use.

Recommended free course

Introduction to Cyber Security

Recommended book

“Hacking: The Art of Exploitation” by Jon Erickson

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