added submission for gusliu

gusliu-assign1/caesar-cipher.txt

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+SBWKRQ

gusliu-assign1/caesar-plain.txt

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+PYTHON

gusliu-assign1/crypto.py

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+"""
+Assignment 1: Cryptography
+Course: CS 92SI
+Name: <Gus Liu>
+Date: <10/7/15>
+
+Replace this with a description of the program.
+"""
+
+def encrypt_caesar(plaintext):
+    """
+    Encrypts plaintext using a Caesar cipher.
+    Add more implementation details here.
+    """
+    encrypted = ''
+    for char in plaintext:
+        ascii = ord(char) + 3
+        if char.isupper():
+            ascii -= ord('A')
+            ascii %= 26
+            encrypted += chr(ord('A') + ascii)
+        else:
+            ascii -= ord('a')
+            ascii %= 26
+            encrypted += chr(ord('a') + ascii)
+    return encrypted
+
+
+def decrypt_caesar(ciphertext):
+    """
+    Decrypts a ciphertext using a Caesar cipher.
+    Add more implementation details here.
+    """
+    encrypted = ''
+    for char in ciphertext:
+        ascii = ord(char) - 3
+        if char.isupper():
+            ascii -= ord('A')
+            if ascii < 0:
+                ascii += 26
+            encrypted += chr(ord('A') + ascii)
+        else:
+            ascii -= ord('a')
+            if ascii < 0:
+                ascii += 26
+            encrypted += chr(ord('a') + ascii)
+    return encrypted
+
+def get_vigenere_key(length, keyword):
+    repeats = length // len(keyword)
+    leftover = length % len(keyword)
+    key = keyword * repeats + keyword[:leftover]
+    return key
+
+def encrypt_vigenere(plaintext, keyword):
+    """
+    Encrypts plaintext using a Vigenere cipher with a keyword.
+    Add more implementation details here.
+    """
+    plaintext = plaintext.upper()
+    keyword = keyword.upper()
+    length = len(plaintext)
+    key = get_vigenere_key(length, keyword)
+    encrypted = ''
+    for i in range(length):
+        pchar = plaintext[i]
+        kchar = key[i]
+        ascii = (ord(pchar) + ord(kchar)) % 26
+        encrypted += chr(ord('A') + ascii)
+    return encrypted
+
+
+
+def decrypt_vigenere(ciphertext, keyword):
+    """
+    Decrypts ciphertext using a Vigenere cipher with a keyword.
+    Add more implementation details here.
+    """
+    ciphertext = ciphertext.upper()
+    length = len(ciphertext)
+    key = get_vigenere_key(length, keyword)
+    decrypted = ''
+    for i in range(length):
+        cchar = ciphertext[i]
+        kchar = key[i]
+        ascii = (ord(cchar) - ord(kchar)) % 26
+        decrypted += chr(ord('A') + ascii)
+    return decrypted
+
+
+def encrypt_railfence(plaintext, num_rails):
+    """
+    Encrypts plaintext using a railfence cipher.
+    Add more implementation details here.
+    """
+    rows = [''] * num_rails
+    length = len(plaintext)
+    for i in range(length):
+        n = i // (num_rails - 1)
+        index = i % (num_rails - 1)
+        if n % 2 != 0:
+            index = num_rails - 1 - index
+        rows[index] += plaintext[i]
+    z = [''.join(x) for x in rows]
+    return ''.join(z)
+
+
+def decrypt_railfence(ciphertext, num_rails):
+    """
+    Encrypts plaintext using a railfence cipher.
+    Add more implementation details here.
+    """
+    lengths = [0] * num_rails
+    rows = [''] * num_rails
+    length = len(ciphertext)
+    row = 0
+    going_down = True
+    for i in range(length):
+        if row == 0:
+            going_down = True
+        if row == num_rails - 1:
+            going_down = False
+        lengths[row] += 1
+        if going_down:
+            row += 1
+        else:
+            row -= 1
+    index = 0
+    for i in range(num_rails):
+        rows[i] = ciphertext[index:index + lengths[i]]
+        index += lengths[i]
+    going_down = True
+    encrypted = ''
+    row = 0
+    for i in range(length):
+        if row == 0:
+            going_down = True
+        if row == num_rails - 1:
+            going_down = False
+        encrypted += (rows[row])[0]
+        rows[row] = (rows[row])[1:]
+        if going_down:
+            row += 1
+        else:
+            row -= 1
+    return encrypted    
+
+
+def read_from_file(filename):
+    """
+    Reads and returns content from a file.
+    Add more implementation details here.
+    """
+    with open(filename, 'r') as f:
+        content = f.read()
+    f.closed
+    return content
+
+
+def write_to_file(filename, content):
+    """
+    Writes content to a file.
+    Add more implementation details here.
+    """
+    with open(filename, 'w') as f:
+        f.write(content)
+    f.close()
+
+
+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("*Input*")
+    input_type = input('(F)ile or (S)tring? ').lower()
+    while True:
+        if input_type == 's':
+            s = input('Enter the string to encrypt: ').lower()
+        elif input_type == 'f':
+            file_name = input('Filename? ')
+            s = read_from_file(file_name).lower()
+        else:
+            continue
+        break
+
+    s = s.replace(" ", "")
+
+    print("*Transform*")
+    transform_type = input('(E)ncrypt or (D)ecrypt? ').lower()
+    while transform_type != 'e' and transform_type != 'd':
+        transform_type = input('(E)ncrypt or (D)ecrypt? ').lower()
+
+    transform_method = input('(C)aesar, (V)igenere, or (R)ailfence? ').lower()
+    while transform_method != 'c' and transform_method != 'v' and transform_method != 'r':
+        transform_method = input('(C)aesar, (V)igenere, or (R)ailfence? ').lower()
+
+    if transform_method == 'c':
+        if transform_type == 'e':
+            print("Encrypting " + s + " using Caesar cipher...")
+            output = encrypt_caesar(s)
+        else:
+            print("Decrypting " + s + " using Caesar cipher...")
+            output = decrypt_caesar(s)
+    elif transform_method == 'v':
+        secret_key = input('Passkey? ')
+        if transform_type == 'e':
+            print("Encrypting " + s + " using Vigenere cipher with key " + secret_key + "...")
+            output = encrypt_vigenere(s, secret_key)
+        else:
+            print("Decrypting " + s + " using Vigenere cipher with key " + secret_key + "...")
+            output = decrypt_vigenere(s, secret_key)
+    elif transform_method == 'r':
+        num_rails = input('Number of rails? ')
+        while not num_rails.isnumeric():
+            num_rails = input('Number of rails? ')
+        num_rails = int(num_rails)
+        if transform_type == 'e':
+            print("Encrypting " + s + " using railfence cipher with " + num_rails + " rails...")
+            output = encrypt_railfence(s, num_rails)
+        else:
+            print("Decrypting " + s + " using railfence cipher with " + num_rails + " rails...")
+            output = decrypt_railfence(s, num_rails)
+
+    print("*Output*")
+    output_type = input('(F)ile or (S)tring? ').lower()
+    while True:
+        if output_type == 's':
+            print(output)
+        elif output_type == 'f':
+            file_name = input('Filename? ')
+            print("Writing ciphertext to " + file_name)
+            write_to_file(file_name, output)
+        else:
+            continue
+        break
+
+
+
+# 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()

gusliu-assign1/feedback.txt

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+Name: <YOUR NAME>
+1) How long did this assignment take you to complete?
+
+
+
+2) What has been the best part of the class so far?
+
+
+
+
+
+3) What can we do to make this class more enjoyable for you?
+
+
+
+
+
+4) What types of assignments would excite you in this class?
+
+
+
+
+

gusliu-assign1/railfence-cipher.txt

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+WECRLTEERDSOEEFEAOCAIVDEN

gusliu-assign1/railfence-plain.txt

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+WE ARE DISCOVERED. FLEE AT ONCE

gusliu-assign1/secret_message.txt

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+KHOORZRUOG

gusliu-assign1/vigenere-cipher.txt

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+LXFOPVEFRNHR

gusliu-assign1/vigenere-plain.txt

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+Attack At Dawn!