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Cryptography Academy: How the locks click.

Every cipher started as the best idea anyone had. Then someone broke it.
This is that story.

Cryptography 101

01. Plaintext

The raw, readable message before any mathematical transformation is applied. It is the vulnerable data you want to protect.

Example

HELLO

02. The Key

The secret parameter that controls the algorithm. While classical ciphers use simple numbers (like a 'Shift' in Caesar) or words, modern systems use highly random, massive strings of bits.

Applying Caesar

SHIFT = 3

03. Ciphertext

The final scrambled output. It appears as random noise and remains completely unintelligible to anyone trying to read it without the correct key.

Result

KHOOR

Crucial Distinction

Encoding is not Encryption. Methods like Morse, Base64 or Hexadecimal do not use a secret key. They simply translate data into a different format so computers can read it. Because there is no key, anyone can reverse the process instantly. Do not use encoding methods to hide secrets.

←Enough theory. Go lock your first message

The Timeline · 650 BC → Today

Tap a node to explore

650 BCTransposition

Scytale

⌬

01 · Curiosity

The Scytale looks suspiciously like a bicycle combination lock. It operates on the exact same idea: align the rings just right and the secret reveals itself without the need for complex mathematics.

02 · Historical Context

Used by Spartan generals around the 5th century BC during military campaigns. A strip of leather or parchment was wound tightly around a wooden rod of a specific diameter. The message was written across the adjacent strips, meaning it could only be read when wrapped around a rod of the exact same size by the receiver.

03 · Technical Foundation

A transposition cipher: letters are not replaced, only reordered. The message is written horizontally across the wound strip, producing columns of letters. When unwound, those columns become scrambled rows. Only a rod of the exact same diameter restores the correct reading order. Mathematically: plaintext arranged in rows of width 'd', ciphertext read column-by-column. A manual matrix transpose. Its weakness is the same as all transposition ciphers: the original letters are all still there, just shuffled. The next leap was to change the letters themselves.

Evolution · The Digital Shift

Modern Foundations

In the digital age, we stopped shifting letters and started processing bits. The core challenge shifted from "how to hide a message" to "how to share a secret key safely."

Symmetric Encryption

The simplest form of encryption. Both Alice and Bob use the 'exact same key' to lock and unlock the message.

Analogy: A single physical key for a house. If you want someone to enter, you must find a way to give them a copy of that key without it being stolen.

Real World: AES-256, Disk Encryption

One Key · High Speed

Asymmetric Encryption

The breakthrough that secures the modern web. Instead of sharing one secret, a mathematical operation generates a 'pair of keys' simultaneously.

Analogy: The Public Key is the slot in a public mailbox, anyone can drop a letter inside. The Private Key is the physical key, only the owner can open the box to read it.

Real World: HTTPS, RSA, WhatsApp

Key Pair Generation

PUBLIC KEYSHARED WITH ALL

ENCRYPTANYONE CAN DO

-->

PRIVATE KEYOWNER ONLY

DECRYPTOWNER ONLY

Cryptographic Hashing

The one-way function. It doesn't hide a message to be read later; it generates a unique, fixed-size 'fingerprint' of the data to verify its integrity.

Analogy: A wax seal on an envelope. You can't read the letter by looking at the seal, but if the seal is broken or changed, you know the letter was tampered with.

Real World: SHA-256, Password Storage, Checksums

ANY DATA

HASH FUNCTION

a591a6d40...

One-Way · Fixed Output

Inflection Point

When Secrets Became Science

For most of history, a cipher was only as strong as how well you could hide it. Then three moments changed everything, and cryptography became a public discipline where the math does the hiding, not the method.

1883

Act I · The Principle

Kerckhoffs's Law

"A system must be secure even if everything about it, except the key, is public knowledge."

This single sentence killed Security by Obscurity as a valid strategy. If your cipher only works while hidden, it was never truly secure.

1949

Act II · The Science

Shannon's Proof

"Communication Theory of Secrecy Systems" formalized cryptography as a branch of mathematics, not an art.

Claude Shannon proved what makes a cipher unbreakable in theory, introducing concepts like confusion and diffusion that define every modern algorithm to this day.

1977+

Act III · The Arena

Open Competitions

Publish the algorithm. Let the world's best cryptanalysts attack it for years. If it survives, it becomes the standard.

DES (1977), AES (2001), SHA-3 (2012), and the ongoing PQC process are all public battles fought in the open.

This is why ciphers have lifespans and status, not just names. The map below is the scoreboard.

The result: a living taxonomy where every algorithm has a category, a purpose, and a verdict.

Each category below solves a fundamentally different problem: keeping data secret, proving identity, or verifying integrity. The status badges reflect the public verdict.

The map is below ↓

Cipher Taxonomy

What each algorithm is for, and whether it's still safe to use.

32 algorithms mapped · tap to expand

Status:⚠ BROKEN◌ LEGACY✓ STANDARD★ MODERN

Note: Status classifications reflect the current consensus from global cryptographic authorities, including NIST (USA), CRYPTREC (Japan), BSI (Germany), and ISO/IEC.

Tip: Tap any cipher for technical details and real-world usage.