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user:dmckinn2:portfolio:cprogproject1 [2012/02/24 16:30] – [Project: SECRET AGENT] dmckinn2user:dmckinn2:portfolio:cprogproject1 [2012/02/26 04:52] (current) – [Project: SECRET AGENT] dmckinn2
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 +======Project: SECRET AGENT======
  
 +A project for C/C++ by Daniel McKinney during the fall 2012.
 +
 +This project was begun on 2/24/12 and is anticipated to take 2 days to complete. Project was completed on 2/25/12.
 +
 +=====Objectives=====
 +create 2 programs, one to enchipher and one to dechipher a statment in a .txt file
 +=====Prerequisites=====
 +In order to successfully accomplish/perform this project, the listed resources/experiences need to be consulted/achieved:
 +
 +  * successful completion of project #0 and solid understanding of pertinent topics
 +  * familiarity with memory allocation via **malloc(3)**
 +  * familiarity with looking up C function parameters/information in the manual
 +  * familiarity with if statements, especially in use for error detection
 +  * familiarity with pointers and pointer arithmetic
 +  * familiarity with loops
 +  * file I/O
 +
 +=====Background=====
 +State the idea or purpose of the project. What are you attempting to pursue?
 +
 +Upon approval, you'll want to fill this section out with more detailed background information. DO NOT JUST PROVIDE A LINK.
 +
 +Providing any links to original source material, such as from a project page, is a good idea.
 +
 +You'll want to give a general overview of what is going to be accomplished (for example, if your project is about installing a web server, do a little write-up on web servers. What is it, why do we need one, how does it work, etc.)
 +
 +=====Scope=====
 +This project will test your familiarity with more involved algorithms, storage, and control structures.
 +
 +Encoding is the process of converting a message into a coded form.
 +
 +Decoding is the reverse- retrieving that original message from an encoded form.
 +
 +In this project you will write a 2 programs: one that will take a plain text message and convert it into a coded form (largely indecipherable to the regular english expecting eye) using a given cipher key, and another that will reverse the process (or decipher), when given the appropriate key.
 +
 +The key is a numeric used to rotate the alphabet a set amount. Where A would normally equal 1, and Z 26, using a cipher key of 1 to shift 1 position to the right; A would now equal 2 (or B), B is now 3 (or C), and Z would be 1 (A).
 +
 +Your encoding program can operate as follows:
 +
 +  * obtains its cipher key from a text file called "key.txt"
 +  * or, if you prefer, use command-line arguments to provide the key
 +  * obtains the input message from a file called "message.txt"
 +  * if "plain.txt" is blank, or does not exist, the program should prompt the user to enter the message via STDIN
 +  * outputs the ciphertext message to STDOUT **AND** saves it to a file called "cipher.txt"
 +  * implement error checking to avoid segfaults
 +
 +The decoding operation is essentially the reverse (shifting to the left). I'd suspect you could reuse much of the same logic.
 +
 +Your decoding program:
 +
 +  * obtains its cipher key from a text file called "key.txt"
 +  * or, if you prefer, use command-line arguments to provide the key
 +  * obtains the input cipher from a file called "cipher.txt"
 +  * if "cipher.txt" is blank, or does not exist, the program should prompt the user to enter the message via STDIN
 +  * outputs the plaintext message to STDOUT **AND** saves it to a file called "plain.txt"
 +  * implement error checking to avoid segfaults
 +
 +If you want, you may implement both functionalities into one program so long as you provide a mechanism for the user to access both operations (but note this is not required for successful completion of this project).
 +
 +=====Code=====
 +
 +The encipher code:
 +
 +<code c>
 +
 +#include<stdio.h>
 +#include<stdlib.h>
 +int main()
 +{
 +        char *message, *cipher, len=0, x, pos=0;
 +        int acipher;
 +        message=(char*) malloc(sizeof(char)*24);
 +        fprintf(stdout,"Enter a message to be encrypted:");
 +        fscanf(stdin, "%s",message);
 +        fprintf(stdout,"Enter a cipher shift integer:");
 +        fscanf(stdin, "%s",cipher);
 +        acipher=atoi(cipher);
 +        x=*(message+pos);
 +        while((x!='\0')&&(x!='\n'))
 +        {
 +                len++;
 +                pos++;
 +                x=*(message+pos);
 +        }
 +        for(pos=0;pos<len;pos++)
 +        {
 +                fprintf(stdout, "%c", *(message+pos)+acipher);
 +        }
 +        fprintf(stdout, "\n");
 +        return(0);
 +}
 +
 +
 +</code>
 +
 +The Decipher code
 +<code c>
 +#include<stdio.h>
 +#include<stdlib.h>
 +int main()
 +{
 +        char *message, *cipher, len=0, x, pos=0;
 +        int acipher;
 +        message=(char*) malloc(sizeof(char)*24);
 +        fprintf(stdout,"Enter a message to be decipher:");
 +        fscanf(stdin, "%s",message);
 +        fprintf(stdout,"Enter a cipher shift integer:");
 +        fscanf(stdin, "%s",cipher);
 +        acipher=atoi(cipher);
 +        x=*(message+pos);
 +        while((x!='\0')&&(x!='\n'))
 +        {
 +                len++;
 +                pos++;
 +                x=*(message+pos);
 +        }
 +        for(pos=0;pos<len;pos++)
 +        {
 +                fprintf(stdout, "%c", *(message+pos)-acipher);
 +        }
 +        fprintf(stdout, "\n");
 +        return(0);
 +}
 +</code>
 +
 +
 +=====Execution=====
 +
 +An example run of the enciphering process:
 +
 +<cli>
 +lab46:~$ ./encipher
 +Enter a message to be encrypted:daniel
 +Enter a cipher shift integer:1
 +ebojfm
 +lab46:~$
 +
 +</cli>
 +
 +Now, we switch gears and decipher a different (previously enciphered) message:
 +
 +<cli>
 +lab46:~$ ./decipher
 +Enter a message to be decipher:daniel
 +Enter a cipher shift integer:1
 +c`mhdk
 +lab46:~$
 +
 +</cli>
 +=====Reflection=====
 +In this project i learned how to shift chars to the right and left, to "encipher" and "decipher" a word.
 +
 +=====References=====
 +In performing this project, the following resources were referenced:
 +
 +  * URL1
 +  * URL2
 +  * URL3 (provides useful information on topic)
 +  * URL4
 +
 +Generally, state where you got informative and useful information to help you accomplish this project when you originally worked on it (from Google, other wiki documents on the Lab46 wiki, etc.)

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