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eiger824 on 02/03/13

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Decrypting Passwords in C++

/ Published in: C++

This is the second and last part of the encryption algorithm that I uploaded last week. It's the other-way-round program: it decrypts a password typed by user.

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#include <iostream>
#include <string.h>
#include <stdlib.h>
#include <sstream>

using namespace std;

void main(){
	//Variable declarations
	int cont=0;
	char password[100]={0};
	int *int_password;
	char real_password[50]={0};
	char *decrypted_password;
	char encrypted_password[100]={0};
	int aux2[2]={0};
	int aux3[3]={0};
	int pos=0;
	int len;

cout<<"Please enter encrypted password: ";
	gets_s(password);//got 'password' char array
	len=strlen(password);
	int_password=new int[len];//initializing pointer to int_password
	for(int i=0;i<len;i++){
		int_password[i]=password[i]-48;//calculating char to int according to ascii table
	}
	cout<<endl;
	for(int i=0;i<len;i++){
		if(password[i]>=48 && password[i]<=57){
			cont++;
		}
		/*if all of the characters are numbers, that means encryption 
		level was simple mode. if any of them is not, then the advanced mode.*/
	}

cout<<endl;
	if(cont==len){ //is simple mode
		cout<<">>Simple-mode encryption type detected."<<endl;
		string stringpassword(password);//converting password into a string-type array
		cout<<"Detected string: "<<stringpassword<<endl;
		cout<<"Length of the string: "<<len<<endl;
		int i=0;
		cout<<endl;
		while(pos<len){
			if(int_password[pos]==1){ //encrypted ascii number has 3 digits 
				int k=0;
				aux3[0]=int_password[pos];
				cout<<"Digit "<<k+1<<" of aux3: "<<aux3[0]<<endl;
				aux3[1]=int_password[pos+1];
				cout<<"Digit "<<k+2<<" of aux3: "<<aux3[1]<<endl;
				aux3[2]=int_password[pos+2];
				cout<<"Digit "<<k+3<<" of aux3: "<<aux3[2]<<endl;
				std::stringstream ss;
				for(int i=0;i<3;i++) ss<<aux3[i];
				int value;
				ss>>value;
				cout<<"Found digit number "<<i+1<<": "<<value<<endl;
				value=value-12;//i now calculate the real ascii number that will correspond to a character
				char value2=value;//conversion from INT to CHAR
				real_password[i]=value2;//assign the int value 'value' to the i position of the password char array
				i++;
				pos=pos+3;
			}
			else{ //encrypted ascii number has 2 digits
				//same process if the encrypted ascii number has 2 digits
				int k=0;
				aux2[0]=int_password[pos];
				aux2[1]=int_password[pos+1];
				cout<<"Digit "<<k+1<<" of aux2: "<<aux2[0]<<endl;
				cout<<"Digit "<<k+2<<" of aux2: "<<aux2[1]<<endl;
				std::stringstream ss;
				for(int i=0;i<2;i++) ss<<aux2[i];
				int value;
				ss>>value;
				cout<<"Found digit number "<<i+1<<": "<<value<<endl;
				value=value-12;
				char value2 = value;
				real_password[i]=value2;
				i++;
				pos=pos+2;
				k++;
			}
		}
		cout<<endl;
		cout<<"Now translating..."<<endl;
		cout<<"\t>>Decrypted password: ";

for(int c=0;c<i;c++){
			cout<<real_password[c];}
		
		cout<<endl;//end of the for loop
	}//end of first condition
	else {
		//is advanced mode
		cout<<">>Advanced-mode encryption type detected."<<endl;
		string stringpassword(password);
		cout<<"Detected string: "<<stringpassword<<endl;
		cout<<"Length of the string: "<<len<<endl;
		
		decrypted_password=new char[len/2];/*on the encryption algorithm, odd    positions were filled with trash characters*/
		for(int i=0;i<len/2;i++){
			decrypted_password[i]=stringpassword[2*i+1]-7;//De-encryption algorithm
		}
		cout<<"Now translating..."<<endl;
		cout<<"\t>>Decrypted password: "; //Print the obtained decrypted password
		for(int c=0;c<len/2;c++){
			cout<<decrypted_password[c];
		}cout<<endl;	
	}
	cout<<"Developed by Santi Pagola."<<endl;
	system("pause");
}

URL: http://programmingeiger824.blogspot.com

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