**Introduction**

It’s encrypted cryptography systems are based on mathematical problems, so complex that cannot be solved without a key somewhere out there’s a bad guy who wants your information in the digital age one of the ways we protect our information is with encryption uses mathematical functions to jumble up our data so badly that no one else can read it unless of course they have a secret key to unjam bêlit again but that doesn‘t stop the bad guys from trying so, it’s important to get it right in this, and the next two articles we’ll get an overview of how encryption works and why it’s important to us we talk about encryption, and the digital age but in truth encryption is not new.

#### The Caesar Cipher

among the earliest known forms of encryption is the Caesar cipher this was used by Julius Caesar when communicating with his generals take this simple phrase that might be sent to a general this is easily readable and is called the plaintext to encrypt this information we take each letter, and we shift it along a certain number of positions Caesar apparently shifted his alphabet by three, so we’ll do the same we then take each letter from the plaintext phrase and substitute it with a shifted letter, so P becomes s R becomes u he becomes H and so on each time we’re shifting by three, letters the result is a jumbled up unreadable sentence this is called the cipher text once the general receives his encrypted message he will need to decrypt it this is a simple case of reversing the process but for this to work the general needs to know how many letters to shift by if he were to shift by anything other than three he won’t be able to decode the original message, so for us the number three is our encryption key we use this number to encrypt the message, and we use it again to grip the message if we want we can use some other numbers our key this is like our password it’s critical that it is keeping secret because anyone who has this key or password can decrypt our messages the Caesar cipher is a type of encryption called a substitution cipher this is because we’re simply substituting one letter for another letter the problem with the caesar cipher is that it’s easily broken especially by today’s standards it’s easily broken as there is only one way to encode each letter in the example we used earlier and II will always encode to an H this was the whole plot point of a Sherlock Holmes story in which Holmes was able to break a substitution cipher by working out which symbols are more common substituting letters in and seeing if they were to make sense and once you’ve worked out a few letters the rest is like a playing wheel of fortune and guessing the rest also as there are only 26 letters in the alphabet, we can only have 25 possible different keys it’s not hard to just try each one of them and to see what happens we call this a brute-force attack I’ve put a few interesting links in the description so, you can read more about this if you are interested.

### The Enigma Machine

fast-forward to the early 20th century and encryption is still being used in warfare however it’s now a lot more complicated this is the Enigma machine it was used by German forces during World War two to make their communications unreadable by enemy forces it looks and acts a lot like an old typewriter the operator would type in their plaintext and lamps would light up showing the cipher text letters this is still a substitution cipher that is it replaces one letter for another letter but it’s much more advanced than the old Caesar cipher as one letter won’t encode to the same encrypted letter every single time, for example, pressing the key may encode to the letter Q press a again and now it might be an s every time a key is pressed the encoding changes each enigma machine has a variety of settings in the front is a plug board that can be rewired into different configurations inside our rotors that turn whenever a key is pressed this is how encoding changes for every key press there are different rotors that can be used, and they can be setup in different orders this combination of settings forms the key if you know which settings were used to encrypt a message you could set up to the machine accordingly and then decrypt the message for a long time this was considered as an unbreakable code there were so many key combinations that it would take a mathematician several lifetimes to brute-force a message in addition to this the keys would change every day many people were working to break the code eventually English mathematician Alan Turing and his team found some success tearing built a machine called the bombe an ancestor of modern computers which was designed specifically to break encryption it would quickly try different key combinations and reject the ones that are obviously wrong this would result in a few likely settings which someone could then work out by hand this was made easier when they found that operators was using very specific phrases in their encrypted messages they would always start with a weather report and always sign-off the same way at the end if you have some ciphertext as well as some plain text that goes with it’s much easier for someone smart enough to find the relationship between the two these days we encrypt all sorts of things not just text messages this happens all the time and you may not even now it thinks of as your web browser when you’re visiting a secure site perhaps online banking it has a padlock symbol meaning that the connection to the web server is secure your web browser is using encryption algorithms and protocols to jumble up the data you’re sending and receiving, and yes there are a lot more advanced than the old substitution ciphers, and that’s just the start we can use encryption to keep transmitted information or information stored on a hard drive private, but the creative ways to use encryption doesn‘t end there a message doesn‘t always need to be a secret, but we often need to confirm that no one has tampered with it encryption can provide us with a way to verify messages integrity and when.

### Encryption Today

you’re online who are you communicating with how do you know the person or server you’re communicating with is in fact genuine encryption can help us here too playing a part in authentication, and no one can ignore the comparatively recent explosion in cryptocurrency yes, you guessed it that uses cryptographic principles too for what actually makes all of this possible essentially it is very large complicated numbers and math the idea is that it’s easy to compute these complicated numbers, and therefore create keys but it’s very difficult to reverse the process think of this simple example take 11 and 13 both of which are prime numbers, and multiply them that’s not hard right you just grab a calculator out, and you type these numbers in, and you get 143 but what if I had had asked you to do the reverse instead what if I asked you to tell me which two prime numbers multiply together to make 143 not so easy now is it and remember that numbers in cryptography are massive while computer could eventually brute-force this it would take multiple lifetimes to do so and by this time whatever they’re trying to break is probably irrelevant anyway, and that is what makes encryption possible by making something so hard that it can’t be figured out in your lifetime so if you’re an IT professional or you’re just someone who’s just plain interested you will probably want to know how these modern forms of encryption work in the real world, so we’re going to take a look into this in a bit more detail in the next two articles, so I hope you’ll join me there