Question

3. File Encryption and Decryption Write a program that uses a dictionary to assign "codes" to each letter of the alphabet. For example: codes-{A':'8','a' :'9', 'B' : e','b' :'#,, etc ) Using this example, the letter A would be assigned the symbol %, the letter a would be assigned the number 9, the letter B would be assigned the symbol e, and so forth. The program should open a specified text file, read its contents, then use the dictionary to write an encrypted version of the file's contents to a second file. Each character in the second file should contain the code for the corresponding character in the first file Write a second program that opens an encrypted file and displays its decrypted contents on the screen.

program must be written in python and have commentary. thank you

Answer 1

Here is the completed code for the two programs. Comments are included, go through it, learn how things work and let me know if you have any doubts or if you need anything to change. If you are satisfied with the solution, please rate the answer. Thanks

#code

#encrypt.py (program to encrypt)

#creating a dictionary, mapping all letters to other codes
enc_dict={'A': '&', 'a': '"', 'B': '#', 'b': '|', 'C': '-', 'c': '<', 'D': "'", 'd': 'l', 'E': '@', 'e': 'z', 'F': 'k', 'f': ')', 'G': 'p', 'g': 'j', 'H': 'u', 'h': 'g', 'I': 'm', 'i': '$', 'J': '}', 'j': '{', 'K': 'd', 'k': 'w', 'L': 'o', 'l': '*', 'M': '/', 'm': ';', 'N': '!', 'n': '%', 'O': 'c', 'o': 'b', 'P': 'y', 'p': '[', 'Q': 't', 'q': 'e', 'R': 'f', 'r': 'x', 'S': '>', 's': 'h', 'T': '(', 't': ']', 'U': '+', 'u': 'v', 'V': '_', 'v': '~', 'W': 'n', 'w': '.', 'X': ':', 'x': '\\', 'Y': '`', 'y': '=', 'Z': 'q', 'z': '^'}
#getting input file name
filename=input('Enter input file name: ')
#opening input file and reading text. assuming input file contains only letters
input_file=open(filename)
text=input_file.read()
#getting output file name and opening it (or creating it)
filename=input('Enter output file name: ')
output_file=open(filename,'w')
#looping through each character of input file
for i in text:
    #if current character is present on enc_dict, taking the corresponding
    #code from dict and writing to output file
    if i in enc_dict:
        output_file.write(enc_dict[i])
    else:
        #else, simply writing the same character to output file (spaces, new lines etc)
        output_file.write(i)
print('Encrypted text has been saved in',filename)
#closing output file
output_file.close()

#decrypt.py (program to decrypt)

#creating a dictionary, mapping all symbols to the original letters

dec_dict={'&': 'A', '"': 'a', '#': 'B', '|': 'b', '-': 'C', '<': 'c', "'": 'D', 'l': 'd', '@': 'E', 'z': 'e', 'k': 'F', ')': 'f', 'p': 'G', 'j': 'g', 'u': 'H', 'g': 'h', 'm': 'I', '$': 'i', '}': 'J', '{': 'j', 'd': 'K', 'w': 'k', 'o': 'L', '*': 'l', '/': 'M', ';': 'm', '!': 'N', '%': 'n', 'c': 'O', 'b': 'o', 'y': 'P', '[': 'p', 't': 'Q', 'e': 'q', 'f': 'R', 'x': 'r', '>': 'S', 'h': 's', '(': 'T', ']': 't', '+': 'U', 'v': 'u', '_': 'V', '~': 'v', 'n': 'W', '.': 'w', ':': 'X', '\\': 'x', '`': 'Y', '=': 'y', 'q': 'Z', '^': 'z'}



filename=input('Enter input file name: ')
#opening input file and reading text
input_file=open(filename)
text=input_file.read()
filename=input('Enter output file name: ')

#creating output file

output_file=open(filename,'w')
#looping through each character in text
for i in text:
    #if current character is present in dec_dict, taking corresponding
    #character from the dict and writing to output file
    if i in dec_dict:
        output_file.write(dec_dict[i])
    else:
        #else. writing the same character (spaces, newlines etc)
        output_file.write(i)
print('Decrypted text has been saved in',filename)

#closing output file
output_file.close()

#output of first program

Enter input file name: input.txt
Enter output file name: output.txt
Encrypted text has been saved in output.txt

#output of second program

Enter input file name: output.txt
Enter output file name: output2.txt
Decrypted text has been saved in output2.txt

#input.txt

supergirl used her x ray vision to find where the treasure is hidden
but when she reached the location, batboy had already took it
and turns out, he had some help from batman and wonderwoman
hey

#output1.txt

hv[zxj$x* vhzl gzx \ x"= ~$h$b% ]b )$%l .gzxz ]gz ]xz"hvxz $h g$llz%
|v] .gz% hgz xz"<gzl ]gz *b<"]$b%, |"]|b= g"l "*xz"l= ]bbw $]
"%l ]vx%h bv], gz g"l hb;z gz*[ )xb; |"];"% "%l .b%lzx.b;"%
gz=

#output2.txt

supergirl used her x ray vision to find where the treasure is hidden
but when she reached the location, batboy had already took it
and turns out, he had some help from batman and wonderwoman
hey