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POCorrupted stack; Bit manipulation with strings; MSVC++
 

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  1. POCorrupted stack; Bit manipulation with strings; MSVC++
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    <p>EDIT: SOLVED. zvbra appears to be right. giving only 4 chars to crypt was causing the problem. Gotta see why is that because i was told getline discarded the last character...</p> <p>Hello fellow stackers.</p> <p>I want to start by saying I tried to debug and solve my problem by myself but (probably due to my lack of knowledge on assembly and pretty much anything in general) i failed at doing so. So I've came here in the hope you will be able to help me :) .</p> <p>I decided to code a simple (I think) encryption program, more of a test than anything else.</p> <p>It's divided in 2 parts:</p> <p>Alghorithm.h (Yeah, I know it's misspelled.) which contains class 'Crypter'</p> <pre><code>#include &lt;iostream&gt; #include &lt;cmath&gt; using namespace std; class Crypter { private: char Crypt[4]; public: Crypter() { getCrypt: cout&lt;&lt;"\nEnter a 4 character password: "; cin.getline(Crypt,5); if (cin.fail()) { cout&lt;&lt;"\n\nError while reading password. 4 CHARACTERS MAXIMUM.\n\n"; cin.sync(); cin.clear(); goto getCrypt; } } void Encrypt(string&amp; data) { for (int i=0; i&lt;data.size();i++) { int offset=i; if (offset&gt;5) { while (offset&gt;5) { offset-=6; } } float base = 2.0f; int testbit=pow(base,offset);//gets bit to test. Ex: if offset= 1 (2^1=2=binary 10) test bit is the 2nd least significant bit if (data[i]!=(data[i]^testbit)) //if testbit is 1 (tested using xOR) { data[i]= data[i]^Crypt[2]; //-&gt; encrypt using xOR Crypt[2] testbit=pow(base,offset+2); if(data[i]!=data[i]^testbit)// then if testbit is 1 (tested using xOR) { data[i]=(data[i]^Crypt[0])+Crypt[3]; //-&gt; encrypt using xOR Crypt[0] then adding crypt[3] } else { data[i]=(data[i]^Crypt[1])+Crypt[1];//-&gt; encrypt using xOR Crypt[1] then adding crypt[1] } } else { data[i]=((data[i]^Crypt[3])^Crypt[0])+Crypt[2];//-&gt; encrypt using xOR Crypt[1] then xOR Crypt[0] and finally adding crypt[1] } } return; } }; </code></pre> <p>and main.cpp </p> <pre><code>#include "Alghorithm.h" int main() { string data="This sentence is going to be encrypted"; Crypter Crypter; cout&lt;&lt;"\nEncrypting..."; Crypter.Encrypt(data); cout&lt;&lt;"\n\nEncryption Successful\n\nEncrypted string: "&lt;&lt;data&lt;&lt;endl; cin.sync(); cin.clear(); } </code></pre> <p>Now you programming experts must be thinking how clumsy my algorithm is and that most parts don't even make sense for a encryption algorithm(which is possible) but pretend it's a nice algorithm that makes total sense.</p> <p>This is the problem:</p> <p>It compiles. It runs. It encryptes the sentence and prints the encrypted version. But right before the program ends (in the screenshots you can see i forgot to return a value in main, but I've fixed that and the problem is did not change a bit) a message pops up(while running through the compiler) in debug mode [Check Screenshots] and 3 in release mode;</p> <p>Most of them warn about an error caused by a corruption in the stack around Crypter 'variable'.</p> <p>I'm not even close to be considered an experienced programmer so I came here asking for your help.</p> <p>Since the error only pops up when the program is ending does it mean it is a problem with the cleanup?</p> <p>I'm totaly lost here. Any responses are appreciated.</p> <p>NOTE: I've also included part of the assembly code (the relevant part) provided by te debugger; Hope it has some use (check my inline comment on the asm code for the 'position' of the error);</p> <p>Criticise my crappy code at will :)( It seems to have a problem since the resultant encrypted string differes from debug to release mode ?:/?.</p> <p>-João</p> <p>Screens:</p> <p><em>How the program looks like before i press ENTER(Debug)</em>: <a href="http://i44.tinypic.com/3ert2.png" rel="nofollow">http://i44.tinypic.com/3ert2.png</a></p> <p><em>How the program looks like before i press ENTER(Release)</em> <a href="http://i42.tinypic.com/2nld45f.png" rel="nofollow">http://i42.tinypic.com/2nld45f.png</a></p> <p><em>Error shown after pressing ENTER (Debug)</em> <a href="http://i41.tinypic.com/bhltoy.png" rel="nofollow">http://i41.tinypic.com/bhltoy.png</a></p> <p><em>1st Error shown after pressing ENTER (Release)</em> <a href="http://i42.tinypic.com/28lchac.png" rel="nofollow">http://i42.tinypic.com/28lchac.png</a></p> <p><em>2nd Error shown after pressing ENTER (Release)</em> <a href="http://i40.tinypic.com/2h3ttmw.png" rel="nofollow">http://i40.tinypic.com/2h3ttmw.png</a></p> <p><em>3rd Error shown after pressing ENTER (Release)</em> <a href="http://i41.tinypic.com/2lc5suw.png" rel="nofollow">http://i41.tinypic.com/2lc5suw.png</a></p> <p><em>ASM Code provided by the debbuger</em> <a href="http://pastebin.com/TTXUn0T2" rel="nofollow">http://pastebin.com/TTXUn0T2</a></p>
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