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Encryption/Decryption Problem

 
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Encryption/Decryption Problem, Homework help needed
PatCPA
13 Oct, 2006 - 01:29 PM
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Hello All! I need some help with this encryption/decryption problem. I am to promt user to to either 'e' encrypt or 'd' decrypt a four digit number. Each digit will be replaced by the sum of the digit plus 7 (modulus 10). Here's what I have so far.

CODE
#include<iostream>
#include<string>
#include<cmath>

using namespace std;

int main()
{
char action; // Prompt user to decide action

int encrypt;
int decrypt;

cout << "Enter 'e' to encrypt or 'd' to decrypt" << endl;
cin >> action; // Get user input for action

if (action == 'e')
{
cout << "Enter a 4-digit number to encrypt: " << endl;
cin >> encrypt;
cout << encrypt << " would be encrypted as " << char1 << char2 << char3 << char4 << endl;
}
else
if (action == 'd')
{
cout << "Enter a 4-digit number to decrypt: " << endl;
cin >> decrypt;
}
else
cout << "INVALID ENTRY! Please enter 'e' to encrypt or 'd to decrypt" << endl;


return 0;
}


This post has been edited by Dark_Nexus: 31 Oct, 2006 - 10:11 PM
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gregoryH
RE: Encryption/Decryption Problem
13 Oct, 2006 - 02:41 PM
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QUOTE(PatCPA @ 13 Oct, 2006 - 02:29 PM) *

Hello All! I need some help with this encryption/decryption problem. I am to promt user to to either 'e' encrypt or 'd' decrypt a four digit number. Each digit will be replaced by the sum of the digit plus 7 (modulus 10). Here's what I have so far.

CODE

int encrypt;
int decrypt;

if (action == 'e')


Pat,

You are using an int as the type then expecting it to match a string... change the type to a char,,,,
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PatCPA
RE: Encryption/Decryption Problem
13 Oct, 2006 - 02:49 PM
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It can process the selection for encryption or decryption. The problem I am having is that when entering a 4-digit number, how do i get it to extract each digit do that I can manipulate it for encryption or decryption?
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gregoryH
RE: Encryption/Decryption Problem
13 Oct, 2006 - 02:56 PM
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so, thats the problem

first, you need to convert your integer into a string... then you can access each digit....

How? lookup the conversion function itoa( ... )
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Amadeus
RE: Encryption/Decryption Problem
13 Oct, 2006 - 03:06 PM
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As a note for portability, itoa() is not defined in ANSI C...it will not be supported by all compilers. It may be easier to take the input as a string, and convert to int using the atol(), which is defined in ANSI C. Well, not easier, but more portable in any case.
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bluesuus
RE: Encryption/Decryption Problem
13 Oct, 2006 - 04:56 PM
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Yo man all u need to do is apply successive division and modulo.e.g lets say u hv 1234 as ur 4digit number.if you take the modulo of it by 10, you will get the last integer which is 4 in this case( 1234%10 ).And also when you divide the number by 10 you will get 123.4( 1234/10 ), so u save the result in an integer so it will be 123 since u have already taken the last digit and stored in a variable. take ur new number and modulo 10 again u will get 3......and so on...
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PatCPA
RE: Encryption/Decryption Problem
14 Oct, 2006 - 03:03 PM
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I need to extract each of the 4 digits entered in order to perform the required operation. Show I change the variables (encrypt/decrypt) to INT or leave it as a strinf? Don't I have to have the variables be INT in order to perform the manipulations?
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gregoryH
RE: Encryption/Decryption Problem
14 Oct, 2006 - 03:28 PM
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QUOTE(PatCPA @ 14 Oct, 2006 - 04:03 PM) *

I need to extract each of the 4 digits entered in order to perform the required operation. Show I change the variables (encrypt/decrypt) to INT or leave it as a strinf? Don't I have to have the variables be INT in order to perform the manipulations?

C/C++ can automatically perform the data type change (since its all binary data anyway), however, bluesuus has offered you the best solution as it savesyou changing the data type.

Based on the initial data type, and the algorithm, it looks like you should perform this using int's.

The algorithm can detect when you have encrypted all digits because the integer division will leave you with a value of zero.
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