Best answer
Encrypt “The key is hidden under the door” using playfair cipher with keyword “domestic”.
Playfair Matrix in step 1 (draw it in step 1 only ) :
| D | O | M | E | S |
| T | I | C | A | B |
| F | G | H | K | L |
| N | P | Q | R | U |
| V | W | X | Y | Z |
Encrypted Message:
Playfair Matrix:
| D | O | M | E | S |
| T | I | C | A | B |
| F | G | H | K | L |
| N | P | Q | R | U |
| V | W | X | Y | Z |
Encrypted Message:
CFARAEBOGCMVOSPNVTAYCFSOMWEP
Ciphertext: CF AR AE BO GC MV OS PN VT AY CF SO MW EP
Step 1: Key matrix (keyword DOMESTIC, I/J together):
| D | O | M | E | S |
| T | I/J | C | A | B |
| F | G | H | K | L |
| N | P | Q | R | U |
| V | W | X | Y | Z |
Step 2: Digraphs. THEKEYISHIDDENUNDERTHEDOOR. A repeated letter inside a pair is split with X (DD becomes DX D…, OO becomes OX O…):
TH EK EY IS HI DX DE NU ND ER TH ED OX OR
Step 3: Encipher (same row: letter to the right; same column: letter below; otherwise: rectangle corners in the same row)
| Pair | Rule | Cipher |
|---|---|---|
| TH | rectangle | CF |
| EK | same column | AR |
| EY | same column (wrap) | AE |
| IS | rectangle | BO |
| HI | rectangle | GC |
| DX | rectangle | MV |
| DE | same row | OS |
| NU | same row (wrap) | PN |
| ND | same column | VT |
| ER | same column | AY |
| TH | rectangle | CF |
| ED | same row | SO |
| OX | rectangle | MW |
| OR | rectangle | EP |
Example: in TH, T is in row 2, column 1 and H in row 3, column 3. T takes the letter in row 2, column 3 (C) and H the letter in row 3, column 1 (F), giving CF.
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