Transposition cipher
A transposition cipher encrypts by rearranging plaintext symbols according to a key without replacing them.
Definition
A transposition cipher changes the positions of plaintext symbols according to a reversible permutation. The symbols themselves remain unchanged, so the ciphertext usually has exactly the same letter counts as the plaintext.
How it works
Rail fence writes text along rows and reads it in another order. Columnar transposition writes text into a grid and reads columns in an order set by a keyword or numerical key. Decryption reconstructs the layout and applies the inverse permutation.
Cryptanalysis
Single transpositions preserve letter frequencies and can expose characteristic fragments when candidate layouts are tested. Repeated or combined transpositions are harder, but classical forms do not provide modern security.
No. It changes their positions; padding symbols may be added only to fill a layout.
Transposition reorders existing symbols, while substitution replaces symbols and normally preserves their positions.