CPE 645 / CS 685

Applied Cryptography

Where Each One Breaks

Type, key, keyspace, and the attack that ends it, side by side for every cipher above.

Comparisondemo

Objectives

Classify each cipher as substitution, transposition, or both.
Match each cipher to the attack that defeats it.
Rank the ciphers by keyspace and explain why the ranking does not predict security.

Steganography

Static site. Every demo computes in your browser, and nothing you type is sent anywhere.

50%

Cipher	Type	Key	Keyspace	Falls to
Caesar	substitution, mono	1 number	25	exhaustive search
Monoalphabetic	substitution, mono	permutation	26! ≈ 2⁸⁸	letter frequency
Playfair	substitution, digraph	5×5 matrix	≈ 2⁸⁴	digraph frequency
Hill (2×2)	substitution, polygraphic	2×2 matrix	157,248	two known plaintext blocks
Vigenère	substitution, poly	keyword, len m	26^m	Kasiski + index of coincidence
Autokey	substitution, poly	primer	26^m	crib dragging
One-time pad	substitution, poly	random, len n	26ⁿ	nothing, unless you reuse the pad
Rail fence / columnar	transposition	rails / word	small	anagramming; frequencies give it away
Product	both, iterated	both	n/a	survives here → becomes DES and AES

Next: the same ciphers with the keys hidden.

step 1/2