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(&quot;====== Triple-DES test ======&quot;);

//encrypt
Serial.print(&quot;Encrypt...&quot;);
unsigned long time = micros();
des.tripleEncrypt(out, in, key);
time = micros() - time;
Serial.print(&quot;done. (&quot;);
Serial.print(time);
Serial.println(&quot; micros)&quot;);
printArray(out);

//decrypt
for (int i = 0; i &lt; 8; i++)
{
  in[i] = out[i];
}
Serial.print(&quot;Decrypt...&quot;);
time = micros();
des.tripleDecrypt(out, in, key);
time = micros() - time;
Serial.print(&quot;done. (&quot;);
Serial.print(time);
Serial.println(&quot; micros)&quot;);
printArray(out);
delay(2000);

}
}

But I don't think getting the correct, Please find the below,

But when I feed manually like below,

...
input.toCharArray(buf, input.length() + 1);
    Serial.println(buf);
//tdesTest();
byte out[8];
byte in[] = {&quot;12345678&quot;}; //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(&quot;====== Triple-DES test ======&quot;);

...

I get the expected output,

score 1 · Accepted Answer · answered Jul 02 '21 at 14:17

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:

Clear the in[] array to a preset state
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

score 1 · Answer 2 · answered Jul 03 '21 at 07:55

#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();


  }
}

Arduino Serial Monitor Input 3DES Encryption

2 Answers2