The Hardware Side of Cryptography

19 May 2008

Implementing Polybius Cipher using PIC16F84

Polybius cipher works the same as Tap Code Cipher. Each letter is represented by its coordinate in lookup table. To fit 26 characters into 5×5 lookup table we rounded down by combining I and J letter inside one cell. The basic lookup table of Polybius Cipher is shown below.

For more convinience usage, you may enlarge that basic lookup table into another 6×6 lookup table. The 6×6 lookup table capables to encapsulate both digits and letters. An outlining example of 6×6 lookup table is shown below.

I wrote a code of Polybius Cipher for PIC16F84 microcontroller using MPLAB v8.0. I’ve verified and simulated the program. It works the same as specification. The program comes in two version, first version implements basic polybius cipher and the second one implements modified (6×6) polybius cipher.

Test Vector:

  • Plain Text = HELLO WORLD
  • Ciher Text = 23 15 31 31 34 52 34 42 31 14

Screenshots are shown Below:

Plain Text Screenshot

Cipher text Screenshot


Source Code v1.0
Source Code v2.0
PIC16F84 Datasheet
Mid-Range Reference Manual
MPLAB v8.0

Polybius Square

Official Website:

1 Comment »

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