Encryption

Encryption is a way to change information so that only certain people can read it. It turns the original message, called plaintext, into a secret form called ciphertext. This helps keep messages safe from people who should not see them.

To encrypt a message, a special secret number, called an encryption key, is used. This key is created by a special set of rules called an algorithm. Only someone with the right key can change the ciphertext back into the original message.

People have used encryption for a long time, especially in the military, to keep important messages private. Today, encryption is used everywhere in computers and the internet. Modern encryption uses two main methods: public-key and symmetric-key. These methods make it very hard for anyone to break the encryption, keeping our information safe.

History

Ancient

One of the earliest ways people hid messages was by replacing symbols, found in an ancient tomb in Egypt around 1900 BC. These symbols needed a special key to understand. This method was used in places like Ancient Greece and Rome, especially for secret military messages. A famous example is the Caesar cipher, where each letter in a message is moved a certain number of places in the alphabet to hide it.

Around 800 AD, a mathematician named al-Kindi found a way to guess these hidden messages by looking at how often each letter appeared. But later, new methods like the polyalphabetic cipher made it harder to guess by changing the hiding rule as the message was written.

19th–20th century

In the late 1700s, Thomas Jefferson thought of a way to hide messages using a wheel-like device called the Jefferson Disk. Though never built, the idea was to mix up letters in a message. A similar tool, the M-94, was made in 1917 and used by the US Army until 1942.

During World War II, the Axis powers used an even more complex machine called the Enigma Machine. Each day, it changed its mixing rule, making it very hard to break. However, the Allies used computers to find smarter ways to solve the puzzle without trying every possible mix.

Modern

Today, encryption helps keep messages safe when we use the Internet. As computers get faster, new ways to hide messages are created. One early method, DES, was broken in 1999 by a special computer built just for that purpose. Now, stronger methods like AES are used, making it almost impossible to guess the hidden message by trying every option. The best way to break these today is by finding special weaknesses in how the hiding works.

Encryption in cryptography

Encryption helps keep information private and safe. When we send important things like passwords over the Internet, we want to make sure only the right person can read them. Encryption changes the information so that only someone with a special key can change it back to understand it.

There are two main ways to do this. In one way, called symmetric-key encryption, the same key is used to change the information and to change it back. Everyone who wants to talk securely needs to have this same key. The German Enigma Machine used a new key every day for this purpose. In the other way, called public-key cryptography, anyone can use a public key to change the information, but only the person who receives it has a special private key to change it back to read it. This method was first described in 1973.

Pretty Good Privacy (PGP) is a free tool for encryption that was created in 1991 and is still used today.

Uses

Encryption has been used for a long time by militaries and governments to keep messages secret. Today, it is also used to protect information in many everyday systems. For example, many companies use encryption to keep data safe when it is being sent or stored on devices like computers and USB flash drives. This helps protect personal information if a laptop or drive is lost or stolen.

Encryption is also important for protecting data when it is sent over networks, such as the Internet or mobile telephones. This prevents unauthorized people from seeing the information as it travels. It is especially useful for e-commerce, wireless microphones, wireless intercom systems, Bluetooth devices, and bank automatic teller machines.

Regulatory compliance

Encryption helps meet rules that protect sensitive information. For example, under the HIPAA Security Rule, encryption is important for protecting electronic health information. There are also rules like the Payment Card Industry Data Security Standard that require encryption for credit card data when it is stored or sent over public networks.

Data erasure

Main article: Data erasure

Instead of slowly deleting data by overwriting it, encryption can make deletion almost instant. This is called crypto-shredding. For example, iOS devices use a special storage area to keep the key needed to unlock data. However, if someone gets physical access to the device, this method alone may not fully protect the information.

Limitations

Encryption helps keep digital data safe in today’s world. As computers get faster, encryption has become stronger too. But there are still some limits to today’s encryption.

The length of the encryption key shows how strong the encryption is. For example, an old method called DES used a key that was only 56 bits long, which isn’t safe anymore because computers can try all the possibilities too quickly.

Quantum computing uses special science ideas to process data very fast—much faster than today’s supercomputers. This speed could break current encryption methods. For example, a common encryption method called RSA uses big numbers that are hard to split apart without a special key. Quantum computers could split these numbers much faster, making the data unsafe. Other methods like elliptic curve cryptography could also be at risk.

Right now, quantum computers are still new and not very powerful. They aren’t ready for everyday use and can’t handle big tasks yet. But scientists, including groups like the National Security Agency, are working on new encryption methods to stay safe in the future. These new methods could help protect data even from future quantum computers.

Attacks and countermeasures

Encryption helps keep information safe, but it is not enough by itself. It mainly protects data when it is stored or being sent, but the data can still be at risk when it is being used or processed, for example, by a cloud service. New ways to work with encrypted data, like homomorphic encryption and secure multi-party computation, are being developed, but they can be slow and use a lot of resources.

Because of these limits, some people try to find ways around encryption. They might try to steal the encrypted data, attack the keys used to unlock it, or even work from inside the system. Other attacks can damage or destroy the data. Some technologies try to make these attacks harder by changing or moving the encrypted data so it is harder to find or attack.

The debate around encryption

The balance between national security and the right to privacy has been discussed for years because encryption is very important in our digital world. The big discussion about encryption began in the 1990s when the US government tried to stop people from using it, saying it could danger security. People have different views: some think strong encryption helps criminals hide online, while others believe it keeps our digital messages safe. This debate became hotter in 2014 when big companies like Apple and Google started using encryption by default on their devices, leading to many disagreements between governments, companies, and users.

Encryption can keep messages secret, but we also need other ways to make sure messages haven’t been changed or faked. This can be done using special checks or signs created by hashing algorithms. Some tools can do both encryption and these checks together. Even though there are standards for encryption tools, using them correctly can be tricky. One small mistake can let someone break the security. Sometimes, attackers can get information without even breaking the encryption, like by watching message patterns or using hidden tricks.