Encryption

People use secret codes to hide information.

This turns a message into nonsense. Only people with a special key can read it. This keeps secrets safe on the internet.

Long ago, soldiers used codes for messages. They would swap one letter for another. This made the words hard to read.

Today, computers use very strong codes. These codes protect your passwords. They also protect things like bank info.

Some codes change every single day. This makes them even harder to break.

It is a smart way to stay safe online.

People use secret codes to hide information. This is called encryption. Encryption turns a message into nonsense. This nonsense is called ciphertext. Only people with a special key can read it. The original message is called plaintext.

Long ago, soldiers used codes for messages. One way was symbol replacement. This swaps one symbol for another. The Caesar cipher was also used. It shifts letters along the alphabet. In 800 AD, a man named al-Kindi studied these codes. He used frequency analysis. This looks at how often letters appear.

Modern computers use even stronger codes. There are two main types of keys. Symmetric-key uses the same key to lock and unlock. Public-key uses a key anyone can use to lock a message. But only one person has the key to unlock it.

Encryption helps keep your passwords safe. It also protects your bank info on the internet. Some codes are used to hide data on a USB drive. This is called data at rest. Encryption also protects data as it moves through networks. This is called data in transit. It is a smart way to stay safe online.

Encryption is a way to hide information so only certain people can read it. It turns a message, called plaintext, into a scrambled form called ciphertext. This does not stop someone from seeing the message. Instead, it makes the content impossible to understand. To turn the nonsense back into a real message, you need a special tool called a key. An algorithm, which is a set of rules, helps create these keys.

Using these tools helps keep secrets safe from people who should not see them.

There are two main ways that encryption works. In a symmetric-key system, the same key is used to both lock and unlock the message. Both people must have this exact same key to talk privately. Another way is called public-key cryptography. In this system, anyone can use a public key to lock a message. However, only the person with the private decryption key can open it. This makes it very useful for sending information to people you have never met.

People have used secret codes for a very long time. One of the oldest ways was symbol replacement. This was found in the tomb of Khnumhotep II in Egypt around 1900 BC. Later, the Caesar cipher became famous for military use. This method shifts letters a certain number of spots in the alphabet. In 800 AD, a mathematician named al-Kindi found a way to crack these codes. He used frequency analysis to look at how often letters appeared in a message.

In the 1900s, machines were built to handle harder tasks. Thomas Jefferson thought of the Wheel Cipher, which used a spool to jumble letters. In 1917, Major Joseph Mauborne made the M-94 device for the US Army. During World War II, the Axis powers used the Enigma Machine. This machine was very complex because the letter combinations changed every single day. The Allies eventually used computing power to help break the Enigma code.

Today, encryption is everywhere in our digital world. It protects your passwords and bank information when you use the internet. This is called protecting data in transit. It also protects data at rest, like files on a USB drive. Modern standards like AES use very large keys to stay safe. Some keys are so big that they cannot be broken by guessing.

Even as computers get faster, new encryption keeps growing to stay ahead.

Encryption is the process of transforming information so that only authorized parties can read it. In the field of cryptography, this process converts original information, known as plaintext, into an alternative form called ciphertext. Encryption does not physically stop someone from intercepting a message. Instead, it denies the intelligible content to any unauthorized interceptor. To perform this transformation, an encryption scheme usually uses an algorithm to generate a pseudo-random encryption key. An authorized recipient can easily decrypt the message using a key provided by the sender. However, breaking a well-designed scheme without a key requires massive computational resources and specialized skills.

There are two primary methods for managing these cryptographic keys: symmetric-key and public-key encryption. In a symmetric-key scheme, the same key is used for both encryption and decryption. This means all communicating parties must possess the exact same key to achieve secure communication. The German Enigma Machine utilized this method by using a new symmetric key every single day. In contrast, public-key cryptography, also known as asymmetric-key encryption, uses different keys. In this system, an encryption key is made public for anyone to use to lock a message. However, only the specific receiving party holds the private decryption key required to read the content. This method was first described in a secret document in 1973, long before the widespread use of modern digital systems.

Historically, encryption began with simple symbol replacement. One of the earliest examples was found in the tomb of Khnumhotep II in Egypt, dating back to 1900 BC. Ancient Greece and Rome later used non-standard symbol replacement for military purposes. A famous development was the Caesar cipher, which shifts plaintext letters a fixed number of positions along the alphabet. Around 800 AD, the Arab mathematician al-Kindi developed frequency analysis to crack such ciphers. This technique involves studying the frequency of letters in ciphertext to determine the shift. To counter this, al-Qalqashandi and Leon Battista Alberti described the polyalphabetic cipher, which varies the substitution alphabet as encryption proceeds.

Mechanical devices eventually replaced manual symbol shifting. Around 1790, Thomas Jefferson theorized the Wheel Cipher, or Jefferson Disk, to secure military correspondence. This device used a spool to jumble messages up to 36 characters. In 1917, US Army Major Joseph Mauborne independently developed the M-94, a similar device used by the military until 1942. During World War II, the Axis powers employed the Enigma Machine, a much more complex version of the M-94. The Enigma's letter combinations switched entirely every day, meaning users thought they had to test over 17,000 combinations within 24 hours to break it. Ultimately, the Allies used computing power to limit the combinations they needed to check, allowing them to break the code.

Modern encryption is essential for security and commerce on the internet. One of the first modern suites, DES, used a 56-bit key with 72,057,594,037,927,936 possible combinations. However, a brute-force attack by the EFF cracked DES in 1999 in just 22 hours and 15 minutes. Today, standards like AES use much larger keys to ensure security. For example, AES in 256-bit mode is extremely strong. A cipher using a 128-bit key or higher cannot be brute-forced because there are 3.4028237e+38 possible keys. When attackers cannot guess the key, they instead look for vulnerabilities in the cipher itself, such as inherent biases or side-channel attacks.

Encryption protects data in two main states: data in transit and data at rest. Data in transit refers to information moving across networks, such as the internet, mobile phones, or Bluetooth devices. Data at rest refers to information stored on physical devices like USB flash drives or computer hard drives. Protecting data at rest is vital because personal records can be exposed if a laptop is lost or stolen. Encryption also enables "crypto-shredding," a method for nearly instantaneous data erasure. On iOS devices, for instance, the cryptographic key is kept in dedicated effaceable storage. If the key is destroyed, the stored data becomes unreadable.

Beyond personal privacy, encryption is a requirement for many legal and professional systems. In 2007, a survey showed that 71% of companies used encryption for data in transit, while 53% used it for data in storage. Many industries must follow strict rules, such as the Payment Card Industry Data Security Standard (PCI DSS), which requires encrypting cardholder data. In healthcare, the HIPAA Security Rule involves encryption for protecting electronic health information. While currently an "addressable" specification, proposed updates in 2024 aim to make encryption mandatory. As computing power grows, especially with the rise of quantum computing, encryption technology must continue to evolve to remain secure.