The 2 pictures are the beginning of the lab. The below is for part 2.

read_file(0, clear_file); // Read in a file with of unknown length, getting the length from the file read. clear_file is a string containing the path to the clear text file. This function returns a char array created with memory allocation.

read_file(len, clear_file); // Where len > zero, reads len chars from a file. clear_file is a string containing the path to the clear text file. This function returns a char array created with memory allocation.

write_file(0, key, key_file); // Writes a string to file until the \0 char is reached. key is the string of random chars and key_file is a string containing the path of the text file.

write_file(len, cipher, cipher_file); // Where len > zero, writes len chars to a file. cipher is the cipher string of chars and cipher_file is a string containing the path of the text file.

The menu in main() should look like:

Encrypt a file:   1
Decrypt a file:   2
Exit:                 3
Enter a choice:

I suggest using a loop in main to show the menu, get a choice from the user and a switch statement to execute the chosen function. For the first two choices, the necessary file names should be read by main() and passed to encrypt() and decrypt(). To generate the random key, the length of the key and a char array pointer are passed to make_rand_key(). After make_rand_key() completes, the char array contains the randomly selected chars. When the user chooses to exit the program by entering 3, the loop should exit.

The make_rand_key() accepts the length of the random key char array and a pointer to this array. This function uses the srand(time(NULL)) function to seed the rand() function and the rand() function to get random chars. The rand() function accepts no argument and returns an integer value between 0 and RAND_MAX (32,767 on most Intel-based computers). The return from rand must be scaled between 0 and 255 and explicitly castes as a char before being added to the char array. The EOF (integer value of -1) must not be selected as one of the chars in the array so it can be read back from a file during the decrypt operation. If EOF is detected as a random char, subtract 1 from the value to make it -2. It may also be a good idea to replace any null (integer value 0). This may interfere with writing to file and should be replaced with 1. A sample function call to make_rand_key is:

make_rand_key(len, key); // Where len > zero, generates and returns a random key of len chars.

The encrypt() function accepts the clear text, random key and cipher text file names as arguments. It reads the clear text files, generates a random key, performs XOR on clear text and random key, producing the cipher text, and writes the cipher text to file. Sample function call for encrypt():

encrypt(clear_file, key_file, cipher_file); // Where the three arguments are strings containing filenames.

The decrypt() function accepts the random key, cipher text and cipher text file names as arguments. It reads the random key and cipher text files. Read the random key first using read_file and either getc (in a loop) or fgets to read the cipher text file due to the possibility of a stray EOF in the cipher file. Sample function for decrypt():
Transcribed Image Text:Part 1: Reading and Writing Complete Files (40 points) The first part of the lab is to write a program to read the complete contents of a file to a string. This code will be used in subsequent coding problems. You will need 3 functions: main(), tead file) and wite file0. The main function contains the driver code. The read file) function reads the complete contents of a file to a string. The wite. file) writes the complete contents of a string to a file. The read file) will require: Open the file for reading Calculating the size of a file Allocating memory to read the file to a string Rewinding the file to the beginning Reading the files contents to the allocated string Close the file There are a few ways to calculate the length of a file. Beware that some of these methods actually get the last position of the input buffer, which may not be the file length for very large files. I suggest using gete(file, name) until EOF is read with a counter. getc) reads one char at a time from a data stream. EOF will be read at the end of the text file. The rewind(file, name) function returns the file pointer to the beginning of the file. You can use getc) or fgets0 to read the file into the string. Writing the file will require: Open the file for writing Write the string to file Close the file You can use putc) or fputs0. There is useful information about C functions at: http://www.cplusplus.com/reference/ and https://www.tutorialspoint.com/c standard library/index.htm The main function should freef) allocated memory before returning. Test your program by reading and writing a few files. Make sure to give the written file different names than the read files so you can compare them. Part 2: One Time Pad Encryption (60 points) One Time Pad (OTP) encryption, when implemented properly, cannot be hacked by cryptanalysis. This method uses the clear text (message to be encrypted), a random key of characters (the same size of the clear text) and the exclusive OR (XOR) operator. The table below contains the truth tables for bitwise XOR operators. This operator works bit-by-bit on C data.
$XOR (^) 1 The table below shows the result of encrypting the clear text A with the random key * using the bit-by-bit XOR bitwise operator. Each bit position in A is XORE with its respective bit in *, producing cipher text k. |char hex bin 01000001 int Clear text A 65 41 XOR Rand key Cipher text k 00101010 01101011 42 2A 107 6B The clear text can be recovered from the cipher text by using the cipher key and the XOR operator as shown in the table below. hex bin 01101011 XOR 00101010 01000001 char int Cipher text k 107 6B Rand key 42 2A Clear text 65 [41 There is an article about OTP at: https://en.wikipedia.org/wiki/One-time pad This project will require the use of the read file() and write file) from Part 1 and the following functions: 1. main function with a menu including 3 choices: encrypt file, decrypt file and exit program. 2. make, rand key(length of key, key) generates a fixed length string of random chars. 3. encrypt(clear file, key file, cipher file) generates a random key using make, randkexO. perform the clear text XOR ket text, byte-by-byte, to produce the cipher text string and write both the random key and cipher text strings to file. 4. decrypt(key file, cipher file, clear file) uses the cipher text XOR random key to recover the original clear text and writes the clear text to a file (make sure to use a different file name than the original file so you can compare the results) Modify the read file) and write file) functions to also accept an integer argument representing a fixed number of bytes to be read or written. This is to specify the number of bytes to be read from the cipher file, which may contain the EOF character, or write to the cipher text file, which may contain null chars. This is necessary because the cipher may contain both EOF and \0 characters. This will be explained further below. Sample function calls to read file) and write fileO:$
Transcribed Image Text:XOR (^) 1 The table below shows the result of encrypting the clear text A with the random key * using the bit-by-bit XOR bitwise operator. Each bit position in A is XORE with its respective bit in *, producing cipher text k. |char hex bin 01000001 int Clear text A 65 41 XOR Rand key Cipher text k 00101010 01101011 42 2A 107 6B The clear text can be recovered from the cipher text by using the cipher key and the XOR operator as shown in the table below. hex bin 01101011 XOR 00101010 01000001 char int Cipher text k 107 6B Rand key 42 2A Clear text 65 [41 There is an article about OTP at: https://en.wikipedia.org/wiki/One-time pad This project will require the use of the read file() and write file) from Part 1 and the following functions: 1. main function with a menu including 3 choices: encrypt file, decrypt file and exit program. 2. make, rand key(length of key, key) generates a fixed length string of random chars. 3. encrypt(clear file, key file, cipher file) generates a random key using make, randkexO. perform the clear text XOR ket text, byte-by-byte, to produce the cipher text string and write both the random key and cipher text strings to file. 4. decrypt(key file, cipher file, clear file) uses the cipher text XOR random key to recover the original clear text and writes the clear text to a file (make sure to use a different file name than the original file so you can compare the results) Modify the read file) and write file) functions to also accept an integer argument representing a fixed number of bytes to be read or written. This is to specify the number of bytes to be read from the cipher file, which may contain the EOF character, or write to the cipher text file, which may contain null chars. This is necessary because the cipher may contain both EOF and \0 characters. This will be explained further below. Sample function calls to read file) and write fileO:

Question

The 2 pictures are the beginning of the lab. The below is for part 2.

read_file(0, clear_file); // Read in a file with of unknown length, getting the length from the file read. clear_file is a string containing the path to the clear text file. This function returns a char array created with memory allocation.
read_file(len, clear_file); // Where len > zero, reads len chars from a file. clear_file is a string containing the path to the clear text file. This function returns a char array created with memory allocation.
write_file(0, key, key_file); // Writes a string to file until the \0 char is reached. key is the string of random chars and key_file is a string containing the path of the text file.
write_file(len, cipher, cipher_file); // Where len > zero, writes len chars to a file. cipher is the cipher string of chars and cipher_file is a string containing the path of the text file.

The menu in main() should look like:

Encrypt a file:   1
Decrypt a file:   2
Exit:                 3
Enter a choice:

I suggest using a loop in main to show the menu, get a choice from the user and a switch statement to execute the chosen function. For the first two choices, the necessary file names should be read by main() and passed to encrypt() and decrypt(). To generate the random key, the length of the key and a char array pointer are passed to make_rand_key(). After make_rand_key() completes, the char array contains the randomly selected chars. When the user chooses to exit the program by entering 3, the loop should exit.

The make_rand_key() accepts the length of the random key char array and a pointer to this array. This function uses the srand(time(NULL)) function to seed the rand() function and the rand() function to get random chars. The rand() function accepts no argument and returns an integer value between 0 and RAND_MAX (32,767 on most Intel-based computers). The return from rand must be scaled between 0 and 255 and explicitly castes as a char before being added to the char array. The EOF (integer value of -1) must not be selected as one of the chars in the array so it can be read back from a file during the decrypt operation. If EOF is detected as a random char, subtract 1 from the value to make it -2. It may also be a good idea to replace any null (integer value 0). This may interfere with writing to file and should be replaced with 1. A sample function call to make_rand_key is:

make_rand_key(len, key); // Where len > zero, generates and returns a random key of len chars.

The encrypt() function accepts the clear text, random key and cipher text file names as arguments. It reads the clear text files, generates a random key, performs XOR on clear text and random key, producing the cipher text, and writes the cipher text to file. Sample function call for encrypt():

encrypt(clear_file, key_file, cipher_file); // Where the three arguments are strings containing filenames.

The decrypt() function accepts the random key, cipher text and cipher text file names as arguments. It reads the random key and cipher text files. Read the random key first using read_file and either getc (in a loop) or fgets to read the cipher text file due to the possibility of a stray EOF in the cipher file. Sample function for decrypt():

Part 1: Reading and Writing Complete Files (40 points)
The first part of the lab is to write a program to read the complete contents of a file to a string. This code
will be used in subsequent coding problems. You will need 3 functions: main(), tead file) and
wite file0. The main function contains the driver code. The read file) function reads the complete
contents of a file to a string. The wite. file) writes the complete contents of a string to a file. The
read file) will require:
Open the file for reading
Calculating the size of a file
Allocating memory to read the file to a string
Rewinding the file to the beginning
Reading the files contents to the allocated string
Close the file
There are a few ways to calculate the length of a file. Beware that some of these methods actually get the
last position of the input buffer, which may not be the file length for very large files. I suggest using
gete(file, name) until EOF is read with a counter. getc) reads one char at a time from a data stream.
EOF will be read at the end of the text file. The rewind(file, name) function returns the file pointer to the
beginning of the file. You can use getc) or fgets0 to read the file into the string. Writing the file will
require:
Open the file for writing
Write the string to file
Close the file
You can use putc) or fputs0. There is useful information about C functions at:
http://www.cplusplus.com/reference/
and
https://www.tutorialspoint.com/c standard library/index.htm
The main function should freef) allocated memory before returning. Test your program by reading and
writing a few files. Make sure to give the written file different names than the read files so you can
compare them.
Part 2: One Time Pad Encryption (60 points)
One Time Pad (OTP) encryption, when implemented properly, cannot be hacked by cryptanalysis. This
method uses the clear text (message to be encrypted), a random key of characters (the same size of the
clear text) and the exclusive OR (XOR) operator. The table below contains the truth tables for bitwise
XOR operators. This operator works bit-by-bit on C data.

XOR (^)
1
The table below shows the result of encrypting the clear text A with the random key * using the bit-by-bit
XOR bitwise operator. Each bit position in A is XORE with its respective bit in *, producing cipher text
k.
|char
hex
bin
01000001
int
Clear text
A
65
41
XOR
Rand key
Cipher text k
00101010
01101011
42
2A
107
6B
The clear text can be recovered from the cipher text by using the cipher key and the XOR operator as
shown in the table below.
hex
bin
01101011
XOR
00101010
01000001
char
int
Cipher text k
107
6B
Rand key
42
2A
Clear text
65
[41
There is an article about OTP at:
https://en.wikipedia.org/wiki/One-time pad
This project will require the use of the read file() and write file) from Part 1 and the following
functions:
1. main function with a menu including 3 choices: encrypt file, decrypt file and exit program.
2. make, rand key(length of key, key) generates a fixed length string of random chars.
3. encrypt(clear file, key file, cipher file) generates a random key using make, randkexO. perform the
clear text XOR ket text, byte-by-byte, to produce the cipher text string and write both the random key and
cipher text strings to file.
4. decrypt(key file, cipher file, clear file) uses the cipher text XOR random key to recover the original
clear text and writes the clear text to a file (make sure to use a different file name than the original file so
you can compare the results)
Modify the read file) and write file) functions to also accept an integer argument representing a fixed
number of bytes to be read or written. This is to specify the number of bytes to be read from the cipher
file, which may contain the EOF character, or write to the cipher text file, which may contain null chars.
This is necessary because the cipher may contain both EOF and \0 characters. This will be explained
further below. Sample function calls to read file) and write fileO:

Accepted Answer

Actually, program is an executable software that runs on a computer.