Practice encrypting and decrypting text using an online library of ciphers

Create your own cipher by combining mathematical operations and encryption protocols

This tool allows users to build an encryption workflow in which the output of one customizable function becomes the input to another, thereby creating undiscovered methods for obscuring information via a series of ciphers.

The science of cryptography, including methods to encrypt data and how to break encryption

Monoalphabetic ciphers use a set of rules to replace each letter with another consistently, making them susceptible to brute force attacks that try every kind of replacement. While more complex ciphers can transform text in less obvious ways, because certain letters are used more often than others, an analysis of letter frequency may reveal patterns that help uncover the rules that make up a cipher.

Watch how the Enigma machine encrypts messages and learn about its critical design flaw

Using settings selected from a series of rotors and a plugboard that let operators swap letters with any of their choosing, the machine lit up the output letter for each letter typed. While this system could generate messages requiring any of 150 quintillion potential keys, the machine's reflector never encrypted a letter as itself, providing an entry point for exploiting the system.

A look at historical ciphers, from the Spartan 'scytale' to the Navajo Code Talkers

From the Greek word for "hidden writing," cryptography in Ancient Greece took the form of batons around which a long strip of leather or parchment was wrapped, after which messages were written. Recipients needed a scytale of the correct width to encircle received ribbons and reveal the message. Members of the Navajo Nation created a code that remained unbroken throughout its use in World War II.

Try out ShieldFont, a specialized web font that swaps the HTML code corresponding to certain onscreen words to protect website content from AI scrapers.

Claude Shannon, for whom Anthropic's AI tools are named, proved the existence of an unbreakable cipher

In the one-time pad approach, the encryption key is randomly generated and of equal length to the plaintext. This randomness ensures that every possible plaintext is equally likely—RBBHN can mean HELLO, SOLVE, CODES, and so on, using a different key—while matching the message and key lengths prevents the appearance of patterns that can be exploited.

The history and operation of SIGABA, the US counterpart of the Nazi Enigma machine

Developed by the US Army and US Navy, over 10,000 of these machines were deployed by the end of World War II to encrypt messages for the armed forces using three series of rotors. The device would continue to be used until the 1950s, while personal computers were shown to possess enough computing power to crack it by 2021.

How hash functions encrypt stored passwords and can be enhanced with 'salt'

Hash functions convert text into unique, random sets of characters, a process that is computationally expensive and time-consuming to undo. Because hashed outputs for many common passwords are publicly listed, some sites use a salt—additional characters appended to a password—before hashing to produce an output that is not known. When entering a password, it is salted and hashed, then checked against the database for a matching hash before permitting login.

View how AES—the global standard for symmetric encryption—works

Established by the National Institute of Standards and Technology in 2001, the Advanced Encryption Standard transforms plaintext into ciphertext using multiple rounds of processing, including substitution, transposition, and mixing. Larger keys undergo more rounds to produce 16-byte blocks of scrambled data, with 256-bit AES keys taking 3.31 × 10⁵⁶ years to decrypt via brute force.

How end-to-end encryption protects messages, even from service providers

Using symmetric and asymmetric cryptography, data is encrypted on the sender's device before being transmitted across application servers that lack the key needed to decrypt it. The message is not decrypted until it reaches the recipient's device, which uses their private key to recover the plaintext. E2EE's effectiveness has led to its adoption by WhatsApp and Signal.

A US Department of Defense research lab developed the technology for the dark web

Although encryption existed to mask the content of communications across the internet before the 1990s, those managing overseas network infrastructure could determine a spy's affiliation based on where they saw data sent to and received from. To keep this information secret, the US Naval Research Laboratory developed onion routing, which enabled anonymized web browsing. The release of the technology to the public obscured sensitive communications further by growing the volume of anonymous data.

The story of Kryptos, the long unsolved cryptographic sculpture outside the CIA's headquarters

Made by American artist Jim Sanborn, the sculpture features four copper plates engraved with messages written with the 26 letters of the Latin alphabet and question marks. The last of these plates was solved in 2025, but the piece remains of interest to cryptoanalysts.

Compression algorithms can reduce file sizes without losing quality by consolidating repeated data or replacing blocks of code with more compact representations, thereby reducing storage demands and improving data transmission rates.

A visual guide to how bitcoin transactions work and rely on cryptography

The "crypto-" in cryptocurrencies like bitcoin refers to the mathematical functions that generate pairs of public and private keys and encrypt data in blocks. When combined, these systems secure transactions on the network, verify digital asset and token transfers, and contribute to end-user anonymity.

Visualize how passkeys, which rely on asymmetric cryptography to authenticate users, work

After using biometrics or a PIN to access the private key stored on a device, it is combined with a random number generated by the site to produce a cryptographic signature. This signature is verified using the site's public key, allowing a user to log in without entering a password. This reduces the risk of fraudulent messages—phishing attacks—and data breaches.

The dark web protects free speech from censorship and authoritarian oversight

Encrypted networks allow users with internet access anywhere in the world to view blocked content and avoid surveillance when communicating evidence of abuse to independent journalists. The same networks can support democracies by helping activists coordinate protests on dark web forums.

Onion routing disguises internet traffic in layers resembling a nesting doll

Data is encrypted at least three times before being sent to a node—a server that can only decrypt one layer. Then, the underlying encrypted data is relayed to another node, and the process repeats until all layers are decrypted. Thousands of possible nodes make it extremely difficult to trace activity within the system.

Trick a large language model into revealing secret passwords over multiple rounds, each with increasing safeguards.

How quantum computers can empower Shor's algorithm to break digital encryption

Secure communications largely rely on numeric keys generated by multiplying two enormous prime numbers together, and it is computationally impractical to determine these primes by trying to divide by every possible one. While Shor's algorithm can provide better guesses for this brute-force approach, it relies on a number that is difficult to determine on classical computers but much easier to calculate using the simultaneous computations enabled by quantum superposition.

Improve your typing speed by retyping classic literature

Why practice with nonsense letters and syllables when you can retype full books you always wanted to read, from Jane Austen and Sir Arthur Conan Doyle to George Orwell and W.E.B. duBois. And it's free.

A mathematical breakdown of how RSA encryption uses prime numbers to encrypt data

This form of asymmetric cryptography uses mathematical functions that rely on the product of two large prime numbers. Because traditional computers struggle to factor such products, obtaining the private keys needed to decrypt messages becomes effectively impossible. This security can be reinforced with larger prime numbers, though this makes encryption more computationally taxing.

Audio deepfake tools can now impersonate anyone in real time

A cybersecurity company developed a tool that mimics a person's voice with no noticeable delay using only publicly available software, hardware, and voice samples, allowing users to have seemingly authentic conversations while pretending to be someone else.

View a library of custom programs that can be loaded onto graphing calculators, including productivity tools, reference materials, games, and interactive applications, such as prom proposals.

Create professional-quality spoken audio from text

Generative AI now makes it possible to create everything from computer-generated written content to beautiful imagery and hyper-realistic videos in seconds from a user’s simple text prompt. Add to that list: High-quality spoken audio, which the AI software company ElevenLabs specializes in. Its natural-sounding speech synthesis and text-to-speech tech can produce human-like speech that mimics a variety of different tones, styles, and accents.

Technical vulnerabilities prevent full-proof anonymity when browsing the dark web

Despite encrypting data and relaying it within the Tor network, traffic between the network exit and the final destination is no longer hidden and can be captured. Law enforcement agencies can also attempt to deanonymize users by monitoring and matching data signal patterns entering and leaving the network via a correlation algorithm.

A timeline of how Claude Code was used to execute cyberespionage

In September 2025, a Chinese state-sponsored group targeted 30 large tech companies, financial institutions, chemical manufacturing companies, and government agencies by manipulating Claude Code, having succeeded in infiltrating a small subset. The cyberattack is believed to have been the first of its scale carried out without major human intervention.

The first compiler to facilitate communication with computers was developed by Grace Hopper

The A-0 program linker automatically translated mathematical symbols into machine-readable binary code. Although it took two years for computer executives to get on board with the idea, the technology was foundational to future programming languages that allowed computers to understand commands written in word-based languages.

Understanding the Diffie-Hellman key exchange, an example of public key cryptography

Published in 1976 by Whitfield Diffie and Martin Hellman, the system involves two parties combining each of their unique private keys with a public key using a mathematical function. The combinations are exchanged and mixed to establish a common key that no third party can determine. The Diffie-Hellman system underlies many encryption protocols for internet traffic.

Watch an ethical hacker provide a tour of the dark web

Cybersecurity researcher John Hammond explores the effectiveness of a dark web search engine, leaks from ransomware group data breaches, and a categorized index of dark web links, including some that are alleged to host malware. Many dark web sites are no longer active or host scams to fool unsuspecting visitors.

The mathematics of quantum-based cryptography, and why existing data is already at risk

Seeing the potential of this technology, some governments and malicious actors are thought to have already started storing encrypted data, in the hopes that quantum computers within the next 10 to 20 years will be able to decrypt it. As of 2022, the National Institute of Standards and Technology had selected four algorithms for inclusion in a quantum-resistant encryption standard.

Explore content on the dark web safely with the Ahmia search engine, which has provided activists with digital addresses to anonymously send files to media outlets.

Explore a gallery of DALL-E creations

OpenAI's text-to-image generator can create content in a wide range of image styles based on simple prompts. Its utility has also given rise to an organic, passionate user base who employ the tool both for fun and for professional purposes.

Learn about the protocols that make navigating the internet possible

While TCP/IP sends data in packets to the correct destination and checks for errors, UDP omits such safety features to speed up data transfer for real-time communication and streaming. Software rules such as HTTP and HTTPS enable the transfer of content on the World Wide Web, while SMTP handles email messages between servers.

Memes are 'ready-made language'

Internet memes—groups of texts with shared core content, medium, and stance—are what we, as creators and consumers, make of them. Through their seemingly innocuous and irreverent design, these "bite-sized" transmissions have become vehicles of misinformation, conspiracy, propaganda, activism, and subversive messaging.

Transformer architecture can recognize and predict patterns in language

The underlying software powering text generation in AI tools associates each word or subword—called a token—with a set of values corresponding to how often it appears near other tokens. By recognizing these associations in prompts, the LLM can infer meaning.

Explore Anthropic Academy, which provides courses on using Claude

The online courses include Claude Code in Action, which teaches software developers how to integrate Claude Code into existing workflows; Claude 101, to learn how Claude can be used to complete everyday tasks; and an AI Fluency series to help educators, instructional designers, and students learn to apply AI in academic settings.

A collection of ancient Mayan glyphs and pictographs

The Maya had a syllabic and pictorial writing style that featured many incredibly detailed glyphs. Click here to check out this ancient writing style (and maybe test out their related phonetic sounds).

Type any prompt and watch Craiyon—the free AI image generator that began in 2021 as DALL·E mini—turn words into pictures.

Comparing ChatGPT with Claude, the latter excels in writing and coding projects

As of December 2025, Claude Code—Anthropic's AI-powered coding assistant—accounts for 54% of the enterprise coding market, and, while subjective, some report that Claude provides more natural-sounding writing. However, ChatGPT can create images and videos, not just generate text, and provides a broader set of applications via custom GPTs.

Explore an optical table to create quantum physics experiments

This interactive teaches users to create quantum experiments through lessons resembling video game levels. Users can also use the virtual lab to visualize landmark quantum experiments like entanglement, teleportation, cryptography, and quantum computing, or create their own experiments with drag-and-drop elements.

In 1822, French scholar Jean-François Champollion deciphered Egyptian hieroglyphs using the Rosetta Stone.

Social media algorithms are shaping real-life language through memes

The evolution of the internet in the early 2000s supercharged the creation and spread of memetic content. Now, highly tuned algorithms on platforms like TikTok and YouTube influence the language, phrasing, and content of creators, which shapes how we use language in the real world.

The AI that creates any picture you want and how it works

Since January 2021, advances in AI research produced a plethora of deep-learning models capable of generating original images from simple text prompts. Researchers at OpenAI, Google, Facebook, and others have developed yet to be released text-to-image tools, and similar models have proliferated online. This video is a primer on how we got here, how the technology works, and its implications.

In recent years, NIST has suggested that passwords no longer be created using a mix of symbols, numbers, and capital and lowercase letters, as was once recommended.

Safely explore historic viruses and other malicious software in the Malware Museum.

Crunching the numbers on the cost of ransomware

This blog is a preview of the 2022 Crypto Crime Report, offering a summary of ransomware activity in 2021, the most active strains of ransomware, and more (w/ data, charts, and illustrations).

An overview of 12 fundamental types of algorithms and the uses for each

These include search algorithms to quickly process and find important information, cryptographic algorithms to secure communications, randomized algorithms—such as Monte Carlo simulations for estimating probabilities of outcomes—and greedy algorithms, which make optimal choices based on available data in a step-by-step fashion, as seen in navigation apps.

Watch a guided video tour of the Museum of Malware Art

The site includes installations, sculptures, textiles, musical pieces, and galleries inspired by malicious software and related technologies, including the ILOVEYOU virus, encryption protocols from ransomware attacks, and the Industroyer malware framework used by Russia to cut power to Ukraine.

Passkeys, a new authentication method, aim to replace traditional passwords

Passkeys use cryptography keys to secure logins without passwords, resisting phishing and risks from data breaches. The FIDO Alliance developed passkeys as a combination of public and private keys for authentication.

Internet sleuths solve secret message on Perseverance rover’s Mars parachute

In 2020, the Perseverance Rover landed on Mars, sending a message for the folks back home on its parachute. It took fewer than six hours for the Internet's collective forces to decode the secret slogan hidden in the parachute's colors and patterns, as well as the geographic coordinates of the earth-bound place where rocketry was perfected.