Encoding and decoding a message.

[knotty walrus]

Let's say that we are given a string: "abcdefg..." and the cipher says it is supposed to + 100 in value so a = 97 + 100 which is 197 which is Å. But let us say that there is such a letterthat gets encoded into \0, what should we do to avoid or deal with this problem? Since it may cut the decoding short as it is returning a the string shorter as it thinks that it has ended.

[low cove]

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[green fulcrum]

\0 is 0

so if cypher is only adding, it's safe

problem may occur with 'del' character though

[knotty walrus]

if it does del

what do you suggest we do to deal with it?

[green fulcrum]

it will do del if original char value is 27, 27 is escape

so it's unlikely

also, they have the same effect I think

[knotty walrus]

**** Original input message:

As much as you can,
Even if you cannot shape your life as you want it,
at least try this:
as much as you can; do not debase it
in excessive contact with the world,
in the excessive movements and talk.

Do not debase it by taking it,
dragging it often and exposing it
to the daily folly
of relationships and associations,
until it becomes burdensome as an alien life.

Constantine P. Cavafy (1913)

**** Encrypted text lines:

~yPΩ↕||4ô½~ZTSy£Åà?'▓¥ºk½[q¥¼ àï3ÿù╤STOq«ôzüä╢╔á}╚&ì╟═tgtΓ:↨ZZ♣\M♠ÄÄü│9hT⌂z&ô├┤à┴/ßì↔
YMNa╚'è|½-╙ú~|S╕≥6±ƒûu÷┼]%▀N^{

**** Decoded text lines (should be identical to original input!):

As much as you can,
Even if you cannot shape your life as you want it,
at least try this:
as much as you can; do

[green fulcrum]

;compile

#include <stdio.h>

int    main(void)
{
    char test[10] = "testline\0";

    printf("%s\n", test);
    test[4] = 127;
    printf("%s\n", test);

    test[4] -= 100;

    printf("%s\n", test);
    return 0;
}

[knotty walrus]

this is the output i am getting, as you can see the \0 seem to be cutting it off

[green fulcrum]

your cypher seems broken

text has 'n' and spaces before but they don't break the program

[knotty walrus]

the cypher is one where it takes a pgm as a cypher

[green fulcrum]

?

[knotty walrus]

it is as intended, like we take an image and use such image to encode or decode a text

space is also taken into consideration

[green fulcrum]

show code pls

[green fulcrum]

what if you try %127 instead of 255?

[knotty walrus]

same problem

same issue

[green fulcrum]

in both encryption and decryption ?

[knotty walrus]

yep

[green fulcrum]

I think I see the problem

you're treating the array as one longitudinal array

so it'll reach '0' on the 50th character

you're supposed to decouple your 0-2500 variable into two 0 50 variables

[knotty walrus]

wut

[green fulcrum]

ah wait

[knotty walrus]

i dont think that matters

let me send u a ss of the image to decode

we use this to decode it, so i just made it into an array to make it simpler to decode

instead of [][] just []

[green fulcrum]

yeah i see that now

[knotty walrus]

[green fulcrum]

I'm trying to figure out the issue there

but have u ran gdb ?

[knotty walrus]

what is gdb

[green fulcrum]

a debugger

[knotty walrus]

ñope

i am owrking on notepad

lol

[green fulcrum]

what happens when you remove that if (result < 0) {
result += 255;
}

[knotty walrus]

returns nonesense

[green fulcrum]

i dont understand why previous n and spaces get cyphered/decyphered correctly and this one would break the program

that's why I think the problem is elsewhere

[knotty walrus]

space as a ascii value

[green fulcrum]

i know

32

but you cyphered spaces before with the same algo

and it goes on

so why break there ?

[knotty walrus]

and there is also some other random value that added with some other value, equates to \0? no?

[green fulcrum]

oh wait

i'm dumb that's the purpose of the image

sometimes it equals 0

[knotty walrus]

yesh yesh

[green fulcrum]

okok

so let's say it's inevitable to sometimes have a char value of 0, or del

you don't want to see that happen

so don't use ascii

[knotty walrus]

bruh

[green fulcrum]

oh you have no other choice

well well

[knotty walrus]

its ok, i will just wait for someone else to enlighten me

[green fulcrum]

good luck on that, I'll think about the problem for a bit

well

are you allowed to modify the values of passArr

[knotty walrus]

no

[green fulcrum]

you sure ? technically creating a passArr is some kind of improvisation

I dont see why you could not push it a bit further

[knotty walrus]

the image you enter is like a token or key

you cannot really go around changing the key itslef

[green fulcrum]

I understand that but I meant inside the functions

like, modify the interpretation of the image

[knotty walrus]

yesh

[green fulcrum]

anyway you could secure an algoritm that ensure a certain value range

not sure about the 128-255 range but if they're all printable make sure it's in there ?

you could also go between 33 and 126

so you modulo 93 and do + 33

and go the opposite way in decypher

[low cove]

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