A brief history of cryptography and why it matters

Cryptography, cyphers, secret codes. Words that summon up images of a world of covert messages, clandestine meetings and international espionage. Those associations were reinforced recently when Queen Elizabeth II of the UK unveiled a commemorative plaque to mark the centenary of GCHQ – the Government Communications Headquarters in Cheltenham, England.

The plaque unveiled by Her Majesty Queen Elizabeth also contained a secret code of its own, which was made up of a series of dots and dashes under letters and numbers in the plaque’s dedication. Taken together the highlighted characters spell out the message hundred years – not the kind of classified material likely to get any spymasters feeling hot under the collar, nor a level of encryption you’d need a quantum computer to decipher. But a fitting touch to this particular memorial.

GCHQ was formed in the aftermath of World War I. It's where the British military’s signals and intelligence units developed expertise in cracking coded German messages – one of which was the so-called Zimmermann telegram of 1917. Zimmermann, the then German Foreign Minister, had concocted a plan to keep the US out of the war by provoking disturbances along the Mexican border. This, it was hoped, would distract attention from US merchant ships being sunk in the Atlantic by German submarines.

But by intercepting and decoding the Zimmermann telegram, British intelligence publicized the German plan, which helped turn public opinion in America toward joining the fight.

The wisdom of the ancients

Despite the illustrious 100-year history of GCHQ, the practice of cryptography actually goes back thousands of years. One of the earliest examples dates back to around 200 BCE and was devised by the Greek historian Polybius. In a Polybius square, letters fill out a grid of 25 spaces and each letter is identified by its coordinates in the square. This allows for strings of numbers to be used as encoded messages that will only make sense to someone with a copy of the same Polybius square.

In the example below, a message reading ‘44 23 15 13 11 44 43 11 44 34 33 44 23 15 32 11 44’ would translate as the cat sat on the mat. Whether Polybius was in possession of either cats or mats, however, is unclear.

According to Nicholas McDonald of the Department of Electrical and Computer Engineering at the University of Utah: “The earliest known text containing components of cryptography originates in the Egyptian town Menet Khufu on the tomb of nobleman Khnumhotep II nearly 4,000 years ago.”

The Spartans were also known to have developed a form of cryptography, based on wrapping parchment around a polygonal cylinder and Julius Caesar used a basic cypher to encode his messages – moving along the alphabet by a pre-agreed number of letters. But there’s a lot more to encryption than making it tricky for people to read your messages and despite its interesting historical roots, it is one of the fundamentals of business and personal life here in the 21st century.

Cryptography is at the heart of all secure digital communications – the emails you send, the websites you visit (well, a growing proportion of them) and the apps you use. It allows for data to be scrambled and rendered unreadable by everyone except the intended recipient. Its use can range from your bank card details being sent to a retailer via their online store to messaging apps such as Whatsapp or Telegram. It’s also hugely important to the internet of things (IoT) where data is seamlessly communicated between smart sensors and corporate networks.

Someone’s knocking at the (back) door

It transpired just a few years ago that international terrorist groups and organized criminal gangs were communicating via encrypted messages. This led to calls from politicians in Europe, the US and beyond for government intelligence services to be given the tools to intercept and read those messages. It’s an issue that was thrust centre stage amid one of America’s worst mass shootings of recent years.

On the morning of 2 December 2015, Syed Rizwan Farook and his wife Tashfeen Malik shot and killed 14 people in the Californian city of San Bernardino. Approximately 20 others were injured. The attackers were tracked down later that day and in an ensuing gun battle were both killed. Determined to find answers regarding the killers’ motives, the FBI soon sought help from Apple to unlock an iPhone belonging to Farook. Apple, however, refused to comply.

A legal row broke out over the obligations, rights and wrongs of tech firms providing a back door to government agencies that would allow them to bypass encryption. The Justice Department described the situation as unfortunate, saying: “Apple continues to refuse to assist the department in obtaining access to the phone of one of the terrorists involved in a major terror attack on US soil.”

It was a view that garnered much support in the public domain but which Apple’s CEO Tim Cook called a “potentially” chilling breach of privacy: “The same engineers who built strong encryption into the iPhone to protect our users would, ironically, be ordered to weaken those protections and make our users less safe.” The problem, as Apple and many others in the tech industry see it, is that providing any kind of back-door access for official use would weaken security.

The end of the (encrypted) world as we know it

The next stage in the development of encryption may involve the use of quantum computers, which will add layers of complexity that are currently not possible. But until quantum cryptography becomes commonplace, there is a fear that this new groundbreaking technology could render current encryption next-to-useless. Attempts to hack encrypted services are thwarted by the use of long, complex prime numbers which can only be determined by the use of cryptography keys.

Encryption effectively shows you the answer to a puzzle or question and will only let you in if you know what the right question is. So, if the answer is 18, the question might be 3x6 or 2x9. But when the answer you’re dealing with is a very long prime number and the calculations are a complex sequence of multiplication, division and subtraction, a simple guess will never crack the code. A series of guesses, using a computer, could take hundreds of years. But a quantum computer could, theoretically, run through all the possible permutations of your encryption keys simultaneously.