Swagman
History
The Swagman cipher system was proposed by American Cryptogram Association (ACA) member BUNYIP, and first appeared in the Sep-Oct 1977 edition of the ACA's magazine The Cryptogram.
Description
It is a transposition cipher using a key square based on a numerical key to mix the plaintext. The key square can be any size between 3x3 and 7x7. To create a cipher a random number is generated using the numbers 1-n where n is the key square width. The key is produced from this number by filling the numbers 1-n into the square such that no digit is repeated in either row or column. For example using the numerical key 41532 the following key square can be produced:
4 1 5 3 2
5 2 1 4 3
2 5 3 1 4
3 4 2 5 1
1 3 4 2 5
The plaintext is next written horizontally using the same number of rows as the key square width and divided into blocks of the same width. If necessary additional letters are added to the text to fill the last row. For example, using the plaintext "Rome didn't create a great empire by having meetings, they did it by killing all those who opposed them", the following table is produced:
R O M E D
R E A T E
G M E E T
T B Y K I
E W H O O
I D N T C
M P I R E
I N G S T
L L I N G
P P O S E
R E A T E
B Y H A V
H E Y D I
A L L T H
D T H E M
A G
I N
D I
O S
X X
The cipher is created by rearranging the letters in each column according to the numeric order of the key square. So in the first column the key is 45231 and the plaintext RRGTE. The first key number, 1, matches plaintext letter E, the second number, 2, matches G, the third matches T followed by R and R in fourth and fifth place to produce EGTRR in the first cipher column. This is repeated for the second column using the key 12543 and the plaintext OEMBW to produce the cipher OEWBM and so on for the remaining columns. The final ciphertext is produced by reading down each column, EGTRR OEWBM ...
Example
Key: 41532 52143 25314 34251 13425
Plaintext: Rome didn't create a great empire by having meetings, they did it by killing all those who opposed them.
41532
52143
25314
34251
13425
Key
ROMED IDNTC REATE AG
REATE MPIRE BYHAV IN
GMEET INGST HEYDI DI
TBYKI LLING ALLTH OS
EWHOO PPOSE DTHEM XX
Plaintext
EOAEI PDISG DEHDH XG
GEYOD IPISC HYLEE DN
TWEEE LPGTE ATYTV OX
RBHTT ILORT RLHAI AS
RMMKO MNNNE BEATM II
Ciphertext
Final ciphertext: EGTRR OEWBM AYEHM EOETK IDETO PILIM DPPLN IIGON SSTRN GCETE DHARB EYTLE HLYHA DETAT HEVIM XDOAI GNXSI
Solving
Solving method: Brute force search.
After selecting the Swagman cipher, the cipher period can be selected from the Cipher Settings drop down menu. Only periods producing a complete grid will appear in the menu. The default setting of 0 will result in all valid periods up to a maximum of 8 being tested.