How To: Encrypt And Decrypt Text In Python

In this article, I'll show you how to create a simplistic AES python based text encryptor. You'll need python 2.7 and PyCrypto (found here). The code is fairly simple, a user enters an encryption key (which basically tells the program how to scramble the text, using an algorithm), then the text to be encrypted. The program takes the key and text and inputs it into the "cryptograph" or code-based algorithm from PyCrypto. PyCrypto can use 16, 24, or 36 character encryption keys, but for the sake of simplicity, I've limited this program to only 16 character keys. Feel free to change it! Just edit the "if countTotal==16" to 24, 36, or all three.

The Code

from Crypto.Cipher import AES
import string
import base64
import time
#import modules
PADDING = '{'
BLOCK_SIZE = 32
pad = lambda s: s + (BLOCK_SIZE - len(s) % BLOCK_SIZE) * PADDING
#prepare crypto method
EncodeAES = lambda c, s: base64.b64encode(c.encrypt(pad(s)))
DecodeAES = lambda c, e: c.decrypt(base64.b64decode(e)).rstrip(PADDING)
#set encryption/decryption variables
loop=5
while loop==5:
     #set up loop, so the program can be rerun again if desired, without restarting
    option=raw_input("Would You Like to Encrypt Or Decrypt Text?\nEncrypt: a\nDecrypt: b\n")
    if option=='a':
        letter=3
        while letter==3:
            secret = raw_input("Please Enter An Encryption Key {must be 16 characters long}: ")
            countTotal= (len(secret))
            if countTotal==16:
                cipher = AES.new(secret)
                letter=0
            else:
                print "Please Ensure The Key You Entered Is 16 Characters In Length\n"
                letter=3
                #this checks the encryption key to ensure it matches the correct length
        # encode a string
        data=raw_input("Please Enter Text You'd Like Encrypted: ")
        encoded = EncodeAES(cipher, data)
        print 'Encrypted string:', encoded
        options=raw_input("Would You Like To Encrypt/Decrypt Again? Y/N\n")
        if options=='y':
            loop=5
        if options=='n':
            loop=0
          
    if option=='b':
      
        encoded=raw_input("Please Enter The Encoded String:\n")
        letter=3
        while letter==3:
            secret=raw_input("Please Enter The Decryption Key:\n")
            countTotal= (len(secret))
            #this checks the encryption key to ensure it matches the correct length
            if countTotal==16:
                cipher = AES.new(secret)
                letter=0
                decoded = DecodeAES(cipher, encoded)
                print 'Decrypted string:', decoded
                options=raw_input("Would You Like To Encrypt/Decrypt Again? Y/N\n")
                if options=='y':
                    loop=5
                if options=='n':
                    loop=0
            else:
                print "Please Ensure The Key You Entered Is 16 Characters In Length\n"
                letter=3
              
if loop==0:
    print "Goodbye!!"
    time.sleep(2)
    exit
    #exits the program if desired by user 

(I've posted the code here as well) 

Other Uses

There are quite a lot of uses for encrypting text, for example, a program that encrypted an email and forwarded it to the receiver. One could even create a program to send encrypted IM's over sites like Facebook and Gmail, then be decrypted on the other end by the same program. Since all you need is the key and an AES decryptor, its quite a simple, efficient way to send and receive encrypted text messages :) 

If you have any other ideas, please comment!