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Found 62 articles with this tag.
DES's 56-bit key became too weak, but the industry didn't design a new cipher. It just ran DES three times. Learn how Triple DES extended the life of the original standard for another two decades.
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.
AES-GCM does two jobs at once: it hides your data AND proves nobody tampered with it. Learn how Galois/Counter Mode combines AES with GHASH authentication to become the default choice for TLS, IPsec, and disk encryption.
AES secures nearly everything: HTTPS traffic, encrypted disks, and government secrets alike. Here's how the Rijndael cipher transforms data, round by round.
Learn about the Affine cipher, a generalization of the Caesar cipher that combines multiplication and addition to create a larger, but still breakable, keyspace.
Argon2 won the 2015 Password Hashing Competition by making brute-force attacks expensive in RAM, not just CPU time. That closes off the GPU and ASIC cracking farms that broke older schemes. Here's how memory-hardness works.
ARIA is South Korea's national block cipher, a close cousin of AES that shares its S-box but mixes bytes with a different, self-inverse diffusion layer. Learn how its alternating rounds, key schedule, and 1/π constants work.
In August 2025, NIST standardized a cipher small enough to run on a battery-powered sensor and simple enough to fit its whole state in five CPU registers. Learn how Ascon's sponge-based permutation delivers real authenticated encryption at a fraction of AES-GCM's footprint.
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.
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.
BLAKE2 and BLAKE3 have emerged as the preferred choice for new applications requiring high-performance hashing
Bruce Schneier designed Blowfish as a free, fast alternative to DES, with a distinctive twist: its own S-boxes are generated from the encryption key itself. Learn how it works and why it's still found in legacy systems today.
Learn about one of the simplest and most widely known encryption techniques, the Caesar cipher.
Camellia is the cipher that stands next to AES in international standards. Learn how this Japanese Feistel design combines byte S-boxes, a linear mixing layer, and key-dependent FL layers to match AES-level security.
CAST-128, also called CAST5, was the default cipher in some versions of PGP and GnuPG. Learn how its three alternating round functions, huge 8x32-bit S-boxes, and key-dependent rotations work, and why its 64-bit block now limits it.
TLS 1.3's second mandatory cipher suite pairs ChaCha20 encryption with the Poly1305 message authenticator, delivering AES-GCM-equivalent security without needing any special hardware. Here's how the pairing works.
What if you already have AES in your system and don't want to bring in a separate hash function just for message authentication? CMAC builds a MAC directly from a block cipher instead.
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.
The Data Encryption Standard ruled cryptography for over two decades. Learn how its Feistel network works, why its 56-bit key ultimately doomed it, and why it still matters as the foundation for 3DES and AES.
Diffie-Hellman solved cryptography's oldest problem: sharing a secret over a channel anyone can watch. Here's the math, and how it still secures the web.
DSA was the U.S. government's answer to a simple question: how do you prove a message came from you, without RSA's patent? Learn how the Digital Signature Algorithm works, and why a single reused number sank Sony's PS3 security.
ECC gets RSA-level security from far smaller keys. Here's the curve math behind it, and why it now powers most of the web.
EdDSA replaced random nonces with deterministic ones, closing off one of ECDSA's worst failure modes. Here's the math behind Ed25519.
ElGamal turns Diffie-Hellman key exchange into full public-key encryption. Here's how the discrete-log problem protects every message it sends.
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.
GOST 28147-89 was the Soviet Union's answer to DES. Learn how its 32-round Feistel design works, why the standard left the S-boxes undefined, and how the modern Magma cipher fixed that.
TLS 1.3 and the Signal Protocol both lean on the same small, elegant primitive to turn a shared secret into however many separate keys they actually need. Here's how HKDF's extract-then-expand design works.
A hash alone can't prove a message wasn't tampered with. Anyone can recompute it. HMAC fixes that by mixing in a secret key, becoming one of the most quietly essential building blocks in TLS, SSH, and beyond.
In March 2025, NIST picked a second code-based algorithm to back up Kyber. This one hides its noise completely differently from McEliece. Learn how HQC masks a public, unscrambled code with pure algebraic randomness instead.
IDEA was one of the first ciphers to mix three completely different mathematical operations within a single round. Learn how this Swiss-designed algorithm became a mainstay of early PGP, and why it eventually gave way to AES.
McEliece has survived over 45 years of cryptanalysis without ever being broken. It's one of NIST's chosen post-quantum standards. Learn how hiding an error-correcting code behind scrambling matrices creates a public-key system quantum computers can't crack.
Ronald Rivest designed MD5 in 1991. By 2004 it was broken. Here's the algorithm, and why real collisions ended its cryptographic career.
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.
What if you could add two numbers together without ever decrypting them? Paillier encryption makes that possible. It's the mathematical trick behind private vote tallying and secure multi-party computation.
For nearly two decades, PBKDF2's answer to password cracking was simple: make every guess expensive by repeating a hash thousands of times. Here's how it works, and why memory-hard successors like Argon2 eventually surpassed it.
Understanding Pretty Good Privacy: Hybrid Encryption for Secure Messaging and Data
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
RC4 was the simplest, fastest cipher of its era. It powered SSL, WEP, and WPA for over a decade before a decade of accumulating bias attacks quietly killed it. Learn how it works and exactly why it's insecure today.
RC5 and RC6 are built from just three operations: addition, XOR, and rotations whose amounts come from the data itself. Learn how Ron Rivest's flexible RC5 led to RC6, an AES finalist.
RSA made public-key cryptography practical for the world. Here's how it works, why it's secure, and where it's headed as quantum computing looms.
Designed by Daniel J. Bernstein as a fast, secure, RC4-free alternative for software encryption, ChaCha20 now secures TLS 1.3 and WireGuard alike. Learn how its add-rotate-XOR "quarter round" builds a full cipher from pure arithmetic.
Schnorr signatures are what DSA might have been if a 20-year patent hadn't gotten in the way. Simpler, provably secure, and now at the heart of Bitcoin's Taproot upgrade: here's how they work.
Serpent finished second in the AES competition, and it was built to be the safest finalist. Learn how 32 rounds of tiny S-boxes and a bitslice design traded speed for one of the largest security margins of any block cipher.
Secure Hash Algorithm 1 was for years one of the most widely used cryptographic hash functions.
The SHA-2 family of cryptographic hash functions is the gold standard for digital security today.
SHA-3, also known as **Keccak** (pronounced 'ketchak'), is the newest member of the Secure Hash Algorithm family standardized by NIST.
Most hash functions give you a fixed-size output no matter what you ask for. SHAKE breaks that rule: it's a hash function you can ask for any amount of output from, built from the same Keccak sponge as SHA-3.
Simon and Speck are two lightweight block ciphers released by the NSA in 2013 for tiny devices. Learn how Simon gets by on AND, rotate, and XOR, how Speck uses add, rotate, and XOR, and why they became some of the most debated ciphers ever published.
Skipjack was the secret NSA cipher inside the Clipper chip, declassified in 1998. Learn how its 32 rounds of alternating rules work on four 16-bit words, and why its 80-bit key and its history make it a cautionary tale.
SM4 is China's national block cipher standard, a 32-round design that updates one 32-bit word at a time. Learn how its byte S-box, rotate-and-XOR mixing, and compact key schedule work, and where the cipher is used.
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.
TEA is a block cipher small enough to write in a few lines of code, and XTEA is its repaired successor. Learn how shifts, additions, and XORs make a working cipher, and how a flaw in TEA's key handling led to a famous console hack.
Threefish is the tweakable block cipher inside the Skein hash function, a SHA-3 finalist. Learn how it builds a strong cipher from just addition, rotation, and XOR on 64-bit words, with no S-boxes at all.
Understanding TLS: The Backbone of Secure Internet Communication
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.
Twofish was Bruce Schneier's answer to Blowfish's biggest weakness, and one of the five finalists in the competition that ultimately chose AES. Learn how its Feistel network, PHT mixing, and key-dependent S-boxes work.
