Transposition & Fractionation
Rearranging the message instead of replacing its letters
Transposition changes symbol positions. Fractionation splits symbols into coordinate components before rearranging them. These methods provide useful comparisons with modern permutations and mixing layers, while their historical variants retain exploitable structure.
Transposition vs Substitution: Substitution replaces letters (A→Q), preserving positions. Transposition keeps letters but moves them (position 1→7). Both methods preserve statistical information — substitution preserves frequency, transposition preserves frequency too. The letters are all still there. Only their arrangement changes.
Rail Fence Cipher — "HELLOWORLD" on 3 rails
Read row by row: HOL · ELWRD · LO → Ciphertext: HOLELWRDLO
Rail Fence transposes a message along a zigzag route. Rail count, offset conventions and message length define the search; there is no universal ten-rail maximum.
Explore columnar transposition and multiple anagramming: rearrange column strips across three synthetic same-key intercepts and compare a different-key control.
Two successive columnar transpositions: historical military use, attack conditions, and modern computerized cryptanalysis; not an unbroken cipher until 2013.
Bifid, described in Delastelle’s 1902 treatise — Felix Delastelle's fractionation cipher that splits Polybius coordinates, transposes them across a period, and recombines.
Trifid cipher (1902) — Felix Delastelle's three-dimensional 3x3x3 extension of the Bifid that fractionates letters into trits and shuffles them across a period.
Fractionated Morse — converts text to Morse, regroups dots, dashes, and separators in trigrams, then substitutes via a keyed alphabet. Broken by trigram stats.
Fleissner turning grille — a transposition cipher used by Germany in WWI. Rotate an interactive mask 90 degrees and contrast it with Cardano steganography.
Myszkowski transposition (1902) — repeated keyword letters share a rank. Encrypt and decrypt interactively, including incomplete final rows, and compare columnar transposition.
Reconstruct the 27 March 1944 RS44 operating procedure with its original example stencil. Animate permitted-cell entry and keyed extraction.
AMSCO from the American Cryptogram Association specification: alternate one-letter and two-letter cells, read keyed columns, and reconstruct an incomplete final row.
Comparing Historical Rearrangement with AES
AES ShiftRows rotates three rows of its byte-state array; the first row stays in place. It works with MixColumns and the other round operations to spread dependencies. This is a conceptual connection to permutation, not evidence of direct descent from columnar transposition.
AES MixColumns is a linear transformation over GF(2⁸). It combines bytes within each column. Bifid instead rearranges coordinate components; the mechanisms are different, although both illustrate mixing.
Diffusion spreads the influence of input information across output components. A pure transposition only moves whole symbols and preserves their frequencies. AES combines permutation and linear mixing with nonlinear substitution and key addition.