I am currently working on an arduino project using a Teensy 3.2.
The project uses some encryption code that exists in the library folder. When building the encryption code, any padding that was needed was hard-coded until the rest of the encryption worked. With the encryption working, I moved to randomize the padding process.
I am currently using the random() function from Wprogram.h.
When using manual padding, the output seems fine. However as soon as the random number generator is used, the output becomes wild and unintelligible.
When using manual padding:
//st is defined as byte[4][4]
st[0][0]=message; //character from original message, usually 'a' for testing
st[0][1]='1';
st[0][2]='2';
st[0][3]='3';
...
st[3][3]='k';
//Output
//set state: a123CDEF89fghijk //state prior to encryption
//encrypted: ⸮$2⸮⸮k6⸮tʠ&⸮⸮ //this should look funny
//decrypted to: a123CDEF89fghijk //matches plaintext
When using random padding, I've tried a few different ways:
//starting off with one random char for ease of testing
//random value seeded by randomSeed(analogRead(7));
st[0][0]=message;
st[0][1]=byte(random(33,127));//using 33 to 127 to avoid non-print chars
st[0][2]='2';
st[0][3]='3';
...
st[3][3]='k';
//-----Also Trying------
//It almost seemed like the data from the random number generator was flawed
//So I put in a scheme to ensure a hard coded character
if(random(100)%2)
st[0][1]='a';
else
st[0][1]='b';
//--------Also trying----------
//Since it seems like it is simply the existance of the random value that is
// problematic, I tried calling it without using it
int randval=random(100);
st[0][0]=message;
st[0][1]='1';
st[0][2]='2';
st[0][3]='3';
...
st[3][3]='k';
//Typical Output
//set state: a123CDEF89fghijk //state prior to encrypting(random char shows)
//encrypted: *3}3⸮⸮⸮⸮⸮⸮⸮⸮⸮N //this should look funny
//decrypted to: ⸮⸮⸮⸮⸮⸮⸮⸮k⸮-⸮⸮ //this should not look funny
From trying several different ways to create a random character and from also seeing that just the existence of the random value is causing trouble. I am suspecting that there is something buggy about how the random() function works on arduino/teensy.
Something else I noticed after setting up the random number and not using it, is that when I remove this line of code I have to recompile a couple of times before the code works correctly again. This is causing me to suspect the function even more or being buggy.
As I noted in the code samples, I am seeding the random number generator with a unused pin. Even though I would suspect it would be an issue here, I have tried a few different pins just to be safe.
So I guess my questions here might be: does anybody know what might be causing this problem or can possibly suggest and alternate way to get a random value?
