This repo contains cryptography application using low-level Assembly language where I implemented an encryption algorithm, namely Columnar Transposition, a form of transposition cipher just like Rail Fence Cipher using two terminals. The input will be given from the first terminal, labeled “input terminal”, and an encrypted or de-crypted version of the input will be sent to the second terminal, labeled “output terminal.”
The input message will always be in the form of “KEY:ABCD#INPUT_STRING*” where ABCD will be a four character key for the Columnar Transposition, and INPUT_STRING will be 16 character message that will be either encrypted or decrypted.I implemented a button to switch between encryption and decryption modes. The microcontroller will be in the encryption mode initially, and if the button pressed it will go into decryption mode. Note that, the button can be pressed as many as desired.
| MODE | Input Terminal | Output Terminal |
|---|---|---|
| Encryption Mode | KEY:DUCK#ITISASAMPLEINPUT* | IAEUIAPNSMITTSLP |
| Decryption Mode | KEY:DUCK#IAEUIAPNSMITTSLP* | ITISASAMPLEINPUT |
Information on Columnar Transposition: https://en.wikipedia.org/wiki/Transposition_cipher