MATLAB: Need help to encrypt and decrypt the RS232 serial port data

Control System ToolboxcryptographyData Acquisition Toolboxrs232xbeezigbee

I am doing project on wireless smart meter using XBee. my aim is to transmit and receive smart meter data from one XBee to another XBee with encryption. So I need help to write code for encrypt at transmit side XBee(RS232 protocol), and code for decrypt at receive side XBee.

Best Answer

function send_encrypted(s, data_to_send)
  %s is to be a serial object, data_to_send is numeric
  data_as_bytes = typecast(data_to_send, 'uint8');
  encrypted_bytes = encrypt_bytes(data_as_bytes);
  cname = uint8(0 + class(data_to_send)); %chars to bytes
  cnamehdr = [uint8(length(cname)), cname];
  enchdr = uint16(length(encrypted_bytes));
  header = [cnamehdr, enchdr];
  fwrite(s, header);
  fwrite(s, encrypted_bytes);
end
function data = receive_encrypted(s)
  %s is the serial connection.
  cnamelen = fread(s, 1, 'uint8');
  cname = char(fread(s, cnamelen, 'uint8'));
  numencbytes = fread(s, 1, 'uint16');
  encbytes = fread(s, numencbytes, 'uint8');
  data = typecast( decrypt_bytes(encbytes), cname);  %turn it back to double
end
function enc = encrypt_bytes(bytes_to_encrypt)
  %magic encryption goes here
  enc = 255 - bytes_to_encrypt;  %this is the encryption
end
function decr = decrypt_bytes(bytes_to_decrypt);
  %magic decryption goes here
  decr = 255 - bytes_to_decrypt;  %this undoes the encryption
end
Extensions would be required to handle more than 65535 bytes of data per transmission, or to transparently handle strings during transmission, or if you wanted to send data with mixed data types.
By the way, you did know that the Zigbee support AES encryption in hardware, right?
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