Arduino Serial Monitor Input 3DES Encryption

Question

I am trying to 3DES encryption using Serial Read, Found this 3DES Sample code in Github,

#include <DES.h>
DES des;
void setup() {
 Serial.begin(9600);
 Serial.println("Hello!");
}
void loop() {
 desTest();
 tdesTest();
 delay(2000);
}
void desTest()
{
 byte out[8];
 byte in[] = { 1, 2, 3, 4, 5, 6, 7, 8 };
 byte key[] = { 0x3b, 0x38, 0x98, 0x37, 0x15, 0x20, 0xf7, 0x5e };
 
 Serial.println();
 Serial.println("========= DES test ==========");
 
 //encrypt
 Serial.print("Encrypt...");
 unsigned long time = micros();
 des.encrypt(out, in, key);
 time = micros() - time;
 Serial.print("done. (");
 Serial.print(time);
 Serial.println(" micros)");
 printArray(out);
 
 //decrypt
 for (int i = 0; i < 8; i++)
 {
 in[i] = out[i];
 }
 Serial.print("Decrypt...");
 time = micros();
 des.decrypt(out, in, key);
 time = micros() - time;
 Serial.print("done. (");
 Serial.print(time);
 Serial.println(" micros)");
 printArray(out);
}
void tdesTest()
{
 byte out[8];
 byte in[] = { 1, 2, 3, 4, 5, 6, 7, 8 };
 byte key[] = { 
 0x3b, 0x38, 0x98, 0x37, 0x15, 0x20, 0xf7, 0x5e, // key A
 0x92, 0x2f, 0xb5, 0x10, 0xc7, 0x1f, 0x43, 0x6e, // key B
 0x3b, 0x38, 0x98, 0x37, 0x15, 0x20, 0xf7, 0x5e, // key C (in this case A)
 };
 
 Serial.println();
 Serial.println("====== Triple-DES test ======");
 
 //encrypt
 Serial.print("Encrypt...");
 unsigned long time = micros();
 des.tripleEncrypt(out, in, key);
 time = micros() - time;
 Serial.print("done. (");
 Serial.print(time);
 Serial.println(" micros)");
 printArray(out);
 
 //decrypt
 for (int i = 0; i < 8; i++)
 {
 in[i] = out[i];
 }
 Serial.print("Decrypt...");
 time = micros();
 des.tripleDecrypt(out, in, key);
 time = micros() - time;
 Serial.print("done. (");
 Serial.print(time);
 Serial.println(" micros)");
 printArray(out);
}
void printArray(byte output[])
{
 for (int i = 0; i < 8; i++)
 {
 if (output[i] < 0x10)
 {
 Serial.print("0");
 }
 Serial.print(output[i], HEX);
 Serial.print(" ");
 }
 Serial.println();
}

I want to get user serial input from Serial Monitor to feed byte in[]. Which will encrypt user input, I will pad user input to 8 Bytes or restrict input to 8.

Library: https://github.com/Octoate/ArduinoDES

Could any one help me to get data from user input.

Edit 1: I was able to read the String to char and feed to byte in[] changed the code,

#include <DES.h>
DES des;
String input;
char buf[30];
void setup() {
 Serial.begin(9600);
 Serial.println("Hello!");
}
void printArray(byte output[])
{
 for (int i = 0; i < 8; i++)
 {
 if (output[i] < 0x10)
 {
 Serial.print("0");
 }
 Serial.print(output[i], HEX);
 Serial.print(" ");
 }
 Serial.println();
}
void loop() {
 while (Serial.available() > 0) {
 String input = Serial.readString(); // read the incoming data as string
 char buf[30];
/*
 input.toCharArray(buf, 9);
 Serial.println(buf);
*/
 input.toCharArray(buf, input.length() + 1);
 Serial.println(buf);
 
 byte out[8];
 byte in[] = {buf};
 Serial.println(buf);
 byte key[] = {
 0x3b, 0x38, 0x98, 0x37, 0x15, 0x20, 0xf7, 0x5e, // key A
 0x92, 0x2f, 0xb5, 0x10, 0xc7, 0x1f, 0x43, 0x6e, // key B
 0x3b, 0x38, 0x98, 0x37, 0x15, 0x20, 0xf7, 0x5e, // key C (in this case A)
 };
 Serial.println();
 Serial.println("====== Triple-DES test ======");
 //encrypt
 Serial.print("Encrypt...");
 unsigned long time = micros();
 des.tripleEncrypt(out, in, key);
 time = micros() - time;
 Serial.print("done. (");
 Serial.print(time);
 Serial.println(" micros)");
 printArray(out);
 //decrypt
 for (int i = 0; i < 8; i++)
 {
 in[i] = out[i];
 }
 Serial.print("Decrypt...");
 time = micros();
 des.tripleDecrypt(out, in, key);
 time = micros() - time;
 Serial.print("done. (");
 Serial.print(time);
 Serial.println(" micros)");
 printArray(out);
 delay(2000);
 }
}

But I don't think getting the correct, Please find the below, enter image description here

But when I feed manually like below,

...
input.toCharArray(buf, input.length() + 1);
 Serial.println(buf);
 //tdesTest();
 byte out[8];
 byte in[] = {"12345678"}; //Manually feeding hardcoding the value need to get the value from serial read to here
 Serial.println(buf);
 byte key[] = {
 0x3b, 0x38, 0x98, 0x37, 0x15, 0x20, 0xf7, 0x5e, // key A
 0x92, 0x2f, 0xb5, 0x10, 0xc7, 0x1f, 0x43, 0x6e, // key B
 0x3b, 0x38, 0x98, 0x37, 0x15, 0x20, 0xf7, 0x5e, // key C (in this case A)
 };
 Serial.println();
 Serial.println("====== Triple-DES test ======");
...

I get the expected output,

enter image description here

• Majenko: majenko.co.uk/blog/reading-serial-arduino
• VinRocka: Hi @Majenko, Thanks for the reply, I can read the serial string from while (Serial.available > 0) { a = Serial.readString(); // read the incoming data as string } But I could not find a way to feed it to the "byte in[ ]" in tdesTest Method due to unable to feed the string.
• Majenko: Well, that all depends on what format your input is in and what format you need to feed into the in array.
• VinRocka: I want to input String from Serial and convert it to Char and feed to in[ ] @Majenko
• Majenko: Yes, I gathered that. But what is in the string, and how does that relate to what would be put into in[]?

Answer 1

From your comments I think I understand what you are after. So, assuming you have read some string into a String object called input and you have an array in[8] to populate you can:

1. Clear the in[] array to a preset state
2. Copy the string content into in[]

As code:

memset(in, 0, 8); // Erase the contents of in[]
input.toCharArray((char *)in, 8); // Copy up to 8 bytes from the string

• Majenko: Comments are not for extended discussion; this conversation has been moved to chat.

Answer 2

#include <DES.h>
DES des;
byte in[8];
String input;
char buf[30];
void setup() {
 Serial.begin(9600);
 Serial.println("Hello!");
}
void tdesTest() {
 byte out[8];
 byte key[] = {
 0x3b, 0x38, 0x98, 0x37, 0x15, 0x20, 0xf7, 0x5e, // key A
 0x92, 0x2f, 0xb5, 0x10, 0xc7, 0x1f, 0x43, 0x6e, // key B
 0x3b, 0x38, 0x98, 0x37, 0x15, 0x20, 0xf7, 0x5e, // key C (in this case A)
 };
 Serial.println();
 Serial.println("====== Triple-DES test ======");
 //encrypt
 Serial.print("Encrypt...");
 unsigned long time = micros();
 des.tripleEncrypt(out, in, key);
 time = micros() - time;
 Serial.print("done. (");
 Serial.print(time);
 Serial.println(" micros)");
 printArray(out);
 //decrypt
 for (int i = 0; i < 8; i++)
 {
 in[i] = out[i];
 }
 Serial.print("Decrypt...");
 time = micros();
 des.tripleDecrypt(out, in, key);
 time = micros() - time;
 Serial.print("done. (");
 Serial.print(time);
 Serial.println(" micros)");
 printArray(out);
 delay(2000);
}
void printArray(byte output[])
{
 for (int i = 0; i < 8; i++)
 {
 if (output[i] < 0x10)
 {
 Serial.print("0");
 }
 Serial.print(output[i], HEX);
 Serial.print(" ");
 }
 Serial.println();
}
void loop() {
 while (Serial.available() > 0) {
 String input = Serial.readString(); // read the incoming data as string
 memset(in, 0, 9); // Erase the contents of in[]
 input.toCharArray((char *)in, 9); // Copy up to 8 bytes from the string
 tdesTest();
 }
}