The Hardware Side of Cryptography

16 May 2008

The Implementation of Tap Code on PIC16F84

Filed under: decoding, encoding, encryption — Tags: , , , , — edipermadi @ 10:20 am

Tap code is a way of propagating information through taps. This way of communication was commonly used by prisoners to communicate each other. Metal bars or walls were the common media to transmit tap code. This cipher is really simple, it was not intended to provide secure communication, it was just another way to transmit information.

The cipher text is encoded by two digits. First taps represent selected row and the second taps represent selected column. The plain text is outlined as 5×5 table. It contains alphabetic cipher except the “K” letter. The “K” letter was omitted to fix alphabetic character into 5×5 table. Therefore, “K” character always represented as “C”. In additition, “X” character was used to to separate each words. The outlining table is shown below.

However, there will be several problem when plain text contain lots of “K” and “X” characters, solve this problem by your self😀 . And remember, never use this terribly weak cipher for your confidential data🙂 .

example:

Plain Text :

PIDGEY BEEDRILL NIDORINO CHARMANDER CHARMELEON CHARIZARD METAPOD

Cipher Text :

35 24 14 22 15 54 53 12 15 15 14 42 24 31 31 53 33 24 14 34 42 24 33 34 53 13 23 11 42 32 11 33 14 15 42 53 13 23 11 42 32 15 31 15 34 33 53 13 23 11 42 24 55 11 42 14 53 32 15 44 11 35 34 14

Screenshots are shown below

Plain Text

Cipher Text

RELATED STUFF

Download:
Source Code v1.0
Source Code v1.1
PIC16F84 Datasheet
Mid-Range Reference Manual
MPLAB v8.0

Reference:
Tap Code

Official Website
Microchip

2 Comments »

  1. can you post the tap code using java language

    Comment by mohammed — 4 December 2010 @ 1:29 am

    • Thank you for visiting my blog.

      You actually may refer to wiki page. Sorry to say, I have no capability in writing Java Code😀

      Comment by edipermadi — 4 December 2010 @ 7:54 pm


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