Cryptology - Unofficial St. Mary's College of California Web Site

10.4. COLUMNAR TRANSPOSITION 193
column by column, following the order given by the keyword. Reading across
the rows then gives the message.
Examples: Encipher or decipher using columnar transposition.
(1) Encipher Here is my very clever secret message using the keyword
cipher.
c i p h e r
H E R E I S
M Y V E R Y
C L E V E R
S E C R E T
M E S S A G
E
Reading down we have the c column: HMCSME, the e column: IREEA, the
h column: EEVRS, the i column: EYLEE, the p column RVECS, and the r
column: SYRTG. Putting these together and regrouping we obtain HMCSM
EIREE AEEVR SEYLE ERVEC SSYRT G.
(2) Encipher Monday morning arrives too early using the keyword simple
filling last row with null m’s.
(3) Decipher DKOEY TGHRT OORAE NTFSO TEIAL GE using the keyword square.
There are 27 letters in the message and 6 in the keyword, so there will be
27 ÷ 6 ≈ 4 full rows and 27%6 = 3 letters in a fifth row. So we will fill in
S Q U A R E
First we fill down the A column (putting in the first four letters of the
message),
S Q U A R E
D
K
O
E