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Found 26 articles with this tag.
Learn about ADFGVX, the German WWI field cipher that combined Polybius-square fractionation with columnar transposition. It was considered so strong that French cryptanalyst Georges Painvin needed weeks to break a message that helped stop a 1918 offensive.
Learn how to break the Affine cipher by brute-forcing its entire 312-key keyspace and scoring each decryption with a common-word heuristic. It's the same strategy that cracks Caesar, just applied to a slightly bigger lock.
Learn about the Affine cipher, a generalization of the Caesar cipher that combines multiplication and addition to create a larger, but still breakable, keyspace.
Learn about the Atbash cipher, one of the oldest known substitution ciphers, where each letter is mirrored to the opposite end of the alphabet.
Learn about the Autokey cipher, the Vigenère variant that fixes the repeating-key weakness by folding the plaintext itself into the key stream. That closes the door on Kasiski examination.
Learn about Bacon's cipher, Francis Bacon's 17th-century biliteral system that hides a secret message not by scrambling it, but by encoding it into which of two typefaces each letter of an innocent-looking cover text uses.
The Beaufort cipher's reciprocal formula (C = K − P instead of Vigenère's C = P + K) looks like it should matter to an attacker. It doesn't: the same Kasiski examination, Index of Coincidence, and chi-squared pipeline that breaks Vigenère breaks Beaufort just as cleanly.
Learn about the Beaufort cipher, a Vigenère variant that flips the subtraction around to become its own inverse. The same formula both encrypts and decrypts.
Learn about the Bifid cipher, Félix Delastelle's fractionating cipher that scrambles a Polybius square's coordinates across an entire message, defeating single-letter frequency analysis far more thoroughly than plain substitution.
Breaking the Caesar Cipher: A Python Journey from Comprehensive to Concise
Learn about one of the simplest and most widely known encryption techniques, the Caesar cipher.
Columnar transposition doesn't hide letters. It just rearranges them, so frequency analysis finds nothing wrong. Learn the attack that actually works: brute-forcing every column order for each candidate key length, scored by common English substrings.
Learn about the columnar transposition cipher, a classic cipher that scrambles the order of letters instead of replacing them. Learn why combining it with substitution led to some of the toughest hand ciphers ever used.
Learn how the Enigma machine worked: the WWII German cipher machine that produced a different substitution alphabet for every single keystroke. Its defeat by Alan Turing and Bletchley Park changed the course of the war.
Learn about the four-square cipher, a digraph substitution cipher that uses four 5x5 grids to encrypt letter pairs without Playfair's awkward same-row and same-column special cases.
Lester Hill brought matrix multiplication to cryptography in 1929. It was the first cipher to encrypt whole blocks of letters at once.
Learn about the Nihilist cipher, the 19th-century Russian revolutionary cipher that turns a Polybius square into a polyalphabetic system by adding coordinate numbers together instead of shifting letters.
Learn about the one-time pad, the only cipher in this series that is mathematically proven unbreakable, and why that proof rests on three conditions that are almost impossible to satisfy in practice.
The Playfair Cipher: A Complete Educational Guide
Learn about the Polybius square, the ancient Greek cipher that turns every letter into a pair of coordinates. It became the foundation for tap codes, telegraph ciphers, and the ADFGVX cipher.
Learn about Mathematical Elegance in Classical Cryptography
A monoalphabetic substitution key is one arbitrary permutation of 26 letters: 26! of them, far too many to brute force and immune to Kasiski or the Index of Coincidence since there's no repeating key. Here's how frequency analysis and a hill-climbing search crack it anyway.
Learn about the monoalphabetic substitution cipher, the general family of ciphers that Caesar, Atbash, and Affine are all special cases of, and why its huge keyspace still isn't enough to make it secure.
Learn about the two-square cipher, a digraph substitution cipher that sits between Playfair's single grid and four-square's four grids: two independently keyed squares, one uniform encryption rule.
For three centuries the Vigenère cipher was called 'le chiffre indéchiffrable.' Learn the two statistical techniques, Kasiski examination and the Index of Coincidence, that finally broke it, and watch them recover a real key letter by letter.
The Vigenère Cipher: A Journey Through History and Modern Applications.
