added submission for wizeng

wizeng/caesar-cipher.txt

@@ -0,0 +1 @@
+SBWKRQ

wizeng/caesar-plain.txt

@@ -0,0 +1 @@
+PYTHON

wizeng/crypto.py

@@ -0,0 +1,302 @@
+"""
+Assignment 1: Cryptography
+Course: CS 92SI
+Name: William Zeng
+Date: 10/9/2015
+
+Provides several functions to encrypt and decrypt text using several encryption algorithms.
+"""
+
+def encrypt_caesar(plaintext):
+    """
+    Encrypts plaintext using a Caesar cipher.
+    Add more implementation details here.
+    """
+
+    ciphertext = "";
+    for letter in plaintext:
+        letter = chr(ord(letter) + 3);
+        if (not letter.isalpha()):
+            letter = chr(ord(letter) - 26);
+        ciphertext += letter;
+    return ciphertext
+
+def decrypt_caesar(ciphertext):
+    """
+    Decrypts a ciphertext using a Caesar cipher.
+    Add more implementation details here.
+    """
+
+    plaintext = "";
+    for letter in ciphertext:
+        letter = chr(ord(letter) - 3);
+        if (not letter.isalpha()):
+            letter = chr(ord(letter) + 26);
+        plaintext += letter;
+    return plaintext
+
+def encrypt_vigenere(plaintext, keyword):
+    """
+    Encrypts plaintext using a Vigenere cipher with a keyword.
+    Add more implementation details here.
+    """
+
+    ciphertext = ""
+    for i in range(0, len(plaintext)):
+        #The following simplifies some of the addition for determining the enciphering
+        #In the middle of the letter 'b' with keyword letter 'L', it's ('b' - 'a' + 'L' - 'A') + 'a' = 'b' + 'L' - 'A'
+        letter = chr(ord(plaintext[i]) + ord(keyword[i % len(keyword)]) - ord('a' if keyword[i % len(keyword)].islower() else 'A'))
+        #In short, this tests whether adding the keyword to the letter makes it need to loop around
+        if ((not letter.isalpha()) or (letter.islower() and plaintext[i].isupper()) or (letter.isupper() and plaintext[i].islower())):
+            letter = chr(ord(letter) - 26);
+        ciphertext += letter;
+    return ciphertext
+
+def decrypt_vigenere(ciphertext, keyword):
+    """
+    Decrypts ciphertext using a Vigenere cipher with a keyword.
+    Add more implementation details here.
+    """
+
+    plaintext = ""
+    for i in range(0, len(ciphertext)):
+        letter = chr(ord(ciphertext[i]) - ord(keyword[i % len(keyword)]) + ord('a' if keyword[i % len(keyword)].islower() else 'A'))
+        if ((not letter.isalpha()) or (letter.islower() and ciphertext[i].isupper()) or (letter.isupper() and ciphertext[i].islower())):
+            letter = chr(ord(letter) + 26);
+        plaintext += letter;
+    return plaintext
+
+def encrypt_railfence(plaintext, num_rails):
+    """
+    Encrypts plaintext using a railfence cipher.
+    Add more implementation details here.
+    """
+
+    if num_rails == 1:
+        return plaintext
+    ciphertext = ''
+    rails = []
+    for i in range(num_rails):
+        rails.append([])
+    counter = 0
+    increase = True
+    for letter in plaintext:
+        rails[counter] += letter
+        if increase:
+            counter += 1
+            if counter == num_rails:
+                counter -= 2
+                increase = not increase
+        else:
+            counter -= 1
+            if counter == -1:
+                counter += 2
+                increase = not increase
+    for rail in rails:
+        ciphertext += ''.join(rail)
+    return ciphertext
+
+
+def decrypt_railfence(ciphertext, num_rails):
+    """
+    Encrypts plaintext using a railfence cipher.
+    Add more implementation details here.
+    """
+
+    if num_rails == 1:
+        return ciphertext
+    plaintext = ''
+    num_on_rails = []
+    for i in range(num_rails):
+        num_on_rails.append(0)
+
+    counter = 0
+    increase = True
+    for letter in ciphertext:
+        num_on_rails[counter] += 1
+        if increase:
+            counter += 1
+            if counter == num_rails:
+                counter -= 2
+                increase = not increase
+        else:
+            counter -= 1
+            if counter == -1:
+                counter += 2
+                increase = not increase
+
+    rails = []
+    startCount = 0
+    endCount = 0
+    for i in range(num_rails):
+        endCount += num_on_rails[i]
+        rails.append(list(ciphertext[startCount:endCount:]))
+        startCount += num_on_rails[i]
+
+    counter = 0
+    increase = True
+    for letter in ciphertext:
+        plaintext += rails[counter].pop(0)
+        if increase:
+            counter += 1
+            if counter == num_rails:
+                counter -= 2
+                increase = not increase
+        else:
+            counter -= 1
+            if counter == -1:
+                counter += 2
+                increase = not increase
+
+    return plaintext
+
+def read_from_file(filename):
+    """
+    Reads and returns content from a file.
+    Add more implementation details here.
+    """
+
+    with open(filename, 'r') as iffy: 
+        content = iffy.readlines()
+    return ' '.join(content) #concatenates all of the lines in the file together as a single string
+
+def write_to_file(filename, content):
+    """
+    Writes content to a file.
+    Add more implementation details here.
+    """
+    with open(filename, 'w') as offy: 
+        offy.write(content)
+
+def clean_input(str):
+    newstr = ''
+    for char in str:
+        if (char.isalpha()):
+            newstr += char
+    return newstr
+
+def run_suite():
+    """
+    Runs a single iteration of the cryptography suite.
+
+    Asks the user for input text from a string or file, whether to encrypt
+    or decrypt, what tool to use, and where to show the output.
+    """
+    print('Welcome to the Cryptography Suite!')
+    print("*Input*")
+    file_or_string = input('(F)ile or (S)tring? ').lower()
+    while not (file_or_string == 'f' or file_or_string == 's'):
+        file_or_string = input('(F)ile or (S)tring? ').lower()
+
+    input_text = ''
+    filename = ''
+    if file_or_string == 'f':
+        filename = input('Filename? ')
+        input_text = read_from_file(filename)
+    else:
+        input_text = input('Enter the string to (en/de)crypt: ')
+
+    input_text = clean_input(input_text)
+
+    print("*Transform*")
+    encrypt_or_decrypt = input('(E)ncrypt or (D)ecrypt? ').lower()
+    while not (encrypt_or_decrypt == 'e' or encrypt_or_decrypt == 'd'):
+        encrypt_or_decrypt = input('(E)ncrypt or (D)ecrypt? ').lower()
+
+    crypt_type = input('(C)aesar, (V)igenere, or (R)ailfence? ').lower()
+    while not (crypt_type == 'c' or crypt_type == 'v' or crypt_type == 'r'):
+        crypt_type = input('(C)aesar, (V)igenere, or (R)ailfence? ').lower()
+
+    inputStr = ''
+    if file_or_string == 'f':
+        inputStr = 'contents of ' + filename
+    else:
+        inputStr = input_text
+
+    encr_or_decr = ''
+    if encrypt_or_decrypt == 'e':
+        encr_or_decr = 'Encrypting'
+    else:
+        encr_or_decr = 'Decrypting'
+
+    cipher = ''
+    passkey = ''
+    rail_num = ''
+    if crypt_type == 'c':
+        cipher = 'Caesar cipher'
+    elif crypt_type == 'v':
+        passkey = input("Passkey? ")
+        cipher = 'Vigenere cipher with key ' + passkey
+    else:
+        rail_num = int(input("Number of rails? "))
+        cipher = 'railfence cipher'
+
+    print(encr_or_decr, inputStr, 'using', cipher)
+    print('...')
+
+    print("*Output*")
+
+    result_text = ''
+    if crypt_type == 'c':
+        if encrypt_or_decrypt == 'e':
+            result_text = encrypt_caesar(input_text)
+        else:
+            result_text = decrypt_caesar(input_text)
+    elif crypt_type == 'v':
+        if encrypt_or_decrypt == 'e':
+            result_text = encrypt_vigenere(input_text, passkey)
+        else:
+            result_text = decrypt_vigenere(input_text, passkey)
+    else:
+        if encrypt_or_decrypt == 'e':
+            result_text = encrypt_railfence(input_text, rail_num)
+        else:
+            result_text = decrypt_railfence(input_text, rail_num)
+
+
+    file_or_string = input('(F)ile or (S)tring? ').lower()
+    while not (file_or_string == 'f' or file_or_string == 's'):
+        file_or_string = input('(F)ile or (S)tring? ').lower()
+
+    if file_or_string == 'f':
+        filename = input('Filename? ')
+        write_to_file(filename, result_text)
+        print('Writing ciphertext to ', filename, '...')
+    else:
+        if encrypt_or_decrypt == 'e':
+            encr_or_decr = 'ciphertext'
+        else:
+            encr_or_decr = 'plaintext'   
+        print('The', encr_or_decr, 'is: ', result_text, '')
+
+
+
+
+
+# Do not modify code beneath this point.
+def should_continue():
+    """
+    Asks the user whether they would like to continue.
+    Responses that begin with a `Y` return True. (case-insensitively)
+    Responses that begin with a `N` return False. (case-insensitively)
+    All other responses (including '') cause a reprompt.
+    """
+    choice = input("Again (Y/N)? ").upper()
+    while not choice or choice[0] not in ['Y', 'N']:
+        choice = input("Please enter either 'Y' or 'N'. Again (Y/N)? ").upper()
+    return choice[0] == 'Y'
+
+
+def main():
+    """Harness for the Cryptography Suite"""
+    print("Welcome to the Cryptography Suite!")
+    run_suite()
+    while should_continue():
+        run_suite()
+    print("Goodbye!")
+
+
+if __name__ == '__main__':
+    """This block is run if and only if the Python script is invoked from the
+    command line."""
+    main()

wizeng/feedback.txt

@@ -0,0 +1,23 @@
+Name: William Zeng
+1) How long did this assignment take you to complete?
+7 hours
+
+
+2) What has been the best part of the class so far?
+Learning about the things that are so much easier to do/use in Python than other languages
+
+
+
+
+3) What can we do to make this class more enjoyable for you?
+Nothing!
+
+
+
+
+4) What types of assignments would excite you in this class?
+Those that cement the concepts in class but focus on a cool topic (i.e. this assignment teaching crypto)
+
+
+
+

wizeng/railfence-cipher.txt

@@ -0,0 +1 @@
+WECRLTEERDSOEEFEAOCAIVDEN

wizeng/railfence-plain.txt

@@ -0,0 +1 @@
+WE ARE DISCOVERED. FLEE AT ONCE

wizeng/secret_message.txt

@@ -0,0 +1 @@
+KHOORZRUOG

wizeng/vigenere-cipher.txt

@@ -0,0 +1 @@
+LXFOPVEFRNHR

wizeng/vigenere-plain.txt

@@ -0,0 +1 @@
+Attack At Dawn!