added submission for jamesc4

jamesc4-assign1/caesar-cipher.txt

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+SBWKRQ

jamesc4-assign1/caesar-plain.txt

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+PYTHON

jamesc4-assign1/crypto.py

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+"""
+Assignment 1: Cryptography
+Course: CS 92SI
+Name: James Cranston
+Date: due 10/9/15 (submitting one day late)
+
+Cryptography program! :)
+"""
+import string
+
+def get_caesar_dict_encrypt():
+    new_alphabet = "XYZ" + string.ascii_uppercase
+    caesar_dict = {}
+
+    # map alphabet characters to those shifted three right, wrapping around
+    for i in range(len(new_alphabet) - 3):
+        caesar_dict[new_alphabet[i]] = new_alphabet[i + 3]
+
+    return caesar_dict
+
+def get_caesar_dict_decrypt():
+    new_alphabet = "XYZ" + string.ascii_uppercase
+    caesar_dict = {}
+
+    # map alphabet characters to those shifted three left, wrapping around
+    for i in range(3, len(new_alphabet)):
+        caesar_dict[new_alphabet[i]] = new_alphabet[i - 3]
+
+    return caesar_dict
+
+def encrypt_caesar(plaintext):
+    """
+    Encrypts plaintext using a Caesar cipher.
+    """
+    letters = ''.join(filter(str.isalpha, plaintext)).upper()
+    caesar_dict = get_caesar_dict_encrypt()
+
+    ciphertext = ""
+
+    # create ciphertext
+    for ch in letters:
+        ciphertext += caesar_dict[ch]
+
+    return ciphertext
+
+
+def decrypt_caesar(ciphertext):
+    """
+    Decrypts a ciphertext using a Caesar cipher.
+    """
+    letters = ''.join(filter(str.isalpha, ciphertext)).upper()
+    caesar_dict = get_caesar_dict_decrypt()
+
+    plaintext = ""
+
+    for ch in letters:
+        plaintext += caesar_dict[ch]
+
+    return plaintext
+
+def format_plaintext_keyword(plaintext, keyword):
+    """
+    Helper for viginere cipher
+    """
+    plaintext = ''.join(filter(str.isalpha, plaintext)).upper()
+    keyword = ''.join(filter(str.isalpha, keyword)).upper()
+    return (plaintext, keyword)    
+
+def get_vigenere_key(keyword, plaintext):
+    """
+    Helper for viginere cipher
+    """
+    key = keyword
+    while len(key) < len(plaintext):
+        key += keyword
+    key = key[:len(plaintext)]
+    return key    
+
+# p, k = 'attack at dawn', '   lemon    '
+# 'LX`OPVE`RNbR'
+
+def encrypt_vigenere(plaintext, keyword):
+    """
+    Encrypts plaintext using a Vigenere cipher with a keyword.
+    """
+    (plaintext, keyword) = format_plaintext_keyword(plaintext, keyword)
+
+    # builds key
+    key = get_vigenere_key(keyword, plaintext)
+
+    ciphertext = ""
+
+    # encrypts the plaintext
+    for i in range(len(key)):
+        ciphertext += chr(ord(plaintext[i]) + ord(key[i]) - ord('A'))
+
+    return ciphertext
+
+
+def decrypt_vigenere(ciphertext, keyword):
+    """
+    Decrypts ciphertext using a Vigenere cipher with a keyword.
+    """
+    (ciphertext, keyword) = format_plaintext_keyword(ciphertext, keyword)
+
+    # builds key
+    key = get_vigenere_key(keyword, ciphertext)
+
+    plaintext = ""
+
+    # decrypts ciphertext
+    for i in range(len(key)):
+        plaintext += chr(ord(ciphertext[i]) - ord(key[i]) + ord('A'))
+
+    return plaintext
+
+
+def encrypt_railfence(plaintext, num_rails):
+    """
+    Encrypts plaintext using a railfence cipher.
+    Performs splicing and ciphertext construction in O(num_rails) time.
+    """
+    letters = ''.join(filter(str.isalpha, plaintext)).upper()
+
+    # edge case if num_rails <= 1 just use plaintext
+    if num_rails <= 1:
+        return letters
+
+    splice_dist = 2 * (num_rails - 1)
+
+    # result string
+    ciphertext = ''
+
+    # splice the plaintext and create ciphertext
+    for i in range(num_rails):
+        # create one list and append to ciphertext
+        if i == 0 or i == num_rails - 1:
+            ciphertext += ''.join(letters[i::splice_dist])
+
+        # create two alternating lists and alternate append to ciphertext
+        else:
+            list1 = list(letters[i::splice_dist])
+            list2 = list(letters[splice_dist - i::splice_dist])
+
+            # add empty string entries to make lists equal length
+            (shorter, longer) = (list1, list2) if len(list1) < len(list2) else (list2, list1)
+            for _ in range(0, len(longer) - len(shorter)):
+                shorter.append('')
+
+            # append alternating characters from list1, list2
+            zipped = zip(list1, list2)
+            for (char1, char2) in zipped:
+                ciphertext += char1 + char2
+
+    return ciphertext
+
+
+def decrypt_railfence(ciphertext, num_rails):
+    """
+    Encrypts plaintext using a railfence cipher.
+    Add more implementation details here.
+    """
+    letters = ''.join(filter(str.isalpha, ciphertext)).upper()
+
+    # edge case if num_rails <= 1
+    if num_rails <= 1:
+        return letters
+
+    # creates two dimensional grid of dimension num_rows * len(ciphertext)
+    n = len(letters)
+    splice_dist = 2 * (num_rails - 1)
+    grid = [['.' for _ in range(n)] for _ in range(num_rails)]
+    idx = 0
+
+    # map ciphertext to grid
+    for i in range(num_rails):
+        for j in range(n):
+            if idx >= n:
+                break;
+
+            # first and last rails
+            if (j - i) % splice_dist == 0:
+                grid[i][j] = letters[idx]
+                idx += 1
+
+            # middle rails
+            if i != 0 and i != num_rails - 1 and (j + i) % splice_dist == 0:
+                grid[i][j] = letters[idx]
+                idx += 1
+
+    # read plaintext from grid
+    direction = 1
+    rail = 0
+    plaintext = ''
+
+    # read plaintext from grid
+    for i in range(n):
+        plaintext += grid[rail][i]
+        if i != 0 and i % (num_rails - 1) == 0:
+            direction *= -1
+        rail += direction
+
+    return plaintext
+
+
+def read_from_file(filename):
+    """
+    Reads and returns content from a file.
+    Add more implementation details here.o
+    """
+    pass  # woops should have decomposed and did these but I didn't have time to after I finished :(
+
+
+def write_to_file(filename, content):
+    """
+    Writes content to a file.
+    Add more implementation details here.
+    """
+    pass  # woops should have decomposed and did these but I didn't have time to after I finished :(
+
+
+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.
+    """
+    # get input format
+    print("*Input*")
+    input_choice = input("(F)ile or (S)tring? ").upper()
+    while not input_choice or input_choice[0] not in ['F', 'S']:
+        input_choice = input("Please enter either 'F' for file or 'S' for string. Again (F/S)? ").upper()
+
+    filename = ""
+    input_text = ""
+
+    # file input
+    if input_choice[0] == "F":
+        filename = input("Filename? ")
+        while not filename or len(filename) < 1:
+            filename = input("Please enter a valid non-empty filename. ")
+        with open(filename, "r") as f:
+            input_text = f.read().replace("\n", "")
+        f.closed
+
+    # string input
+    else:
+        input_text = input("Enter a string: ")
+
+    # get transformation type
+    print("...\n*Transform*")
+    transform_choice = input("(E)ncrypt or (D)ecrypt? ").upper()
+    while not transform_choice or transform_choice[0] not in ["E", "D"]:
+        transform_choice = input("Please enter either 'E' for encrypt or 'D' for decrypt. Again (E/D? ").upper()
+
+    output_text = ""
+
+    # encryption
+    if transform_choice[0] == "E":
+        encrypt_choice = input("(C)aesar, (V)igenere, or (R)ailfence? ").upper()
+        while not encrypt_choice or encrypt_choice[0] not in ["C", "V", "R"]:
+            encrypt_choice = input("Plese enter either 'C' for Caesar, 'V' for Viginere, or 'R' for railfence. Again(C/V/R) ").upper()
+        method = "Caesar" if encrypt_choice[0] == "C" else "Viginere" if encrypt_choice[0] == "V" else "railfence"
+
+        # Caesar cipher encryption
+        if encrypt_choice == "C":
+            print("Encrypting '{0}' using {1} cipher".format(input_text, method))
+            output_text = encrypt_caesar(input_text)
+
+        # Viginere cipher encryption
+        elif encrypt_choice == "V":
+            passkey = input("Passkey? ")
+            while not passkey or len(passkey) < 1:
+                passkey = input("Please enter a valid passkey? ")
+            print("Encrypting '{0}' using {1} cipher with key {2}".format(input_text, method, passkey))
+            output_text = encrypt_viginere(input_text, passkey)
+
+        # railfence cipher encryption
+        else:
+            num_rails = int(input("How many (positive integer) rails? "))
+            while not num_rails or int(num_rails) < 1:
+                num_rails = input("How many (positive integer) rails? ")
+            print("Encrypting '{0}' using {1} with {2} rails".format(input_text, method, num_rails))
+            output_text = encrypt_railfence(input_text, num_rails)
+
+    # decryption
+    else:
+        decrypt_choice = input("(C)aesar, (V)igenere, or (R)ailfence? ").upper()
+        while not decrypt_choice or decrypt_choice[0] not in ["C", "V", "R"]:
+            decrypt_choice = input("Plese enter either 'C' for Caesar, 'V' for Viginere, or 'R' for railfence. Again(C/V/R) ").upper()
+        method = "Caesar" if decrypt_choice[0] == "C" else "Viginere" if decrypt_choice[0] == "V" else "railfence"
+        source = filename if input_choice == "F" else input_text
+
+        # Caesar cipher decryption
+        if decrypt_choice == "C":
+            print("Decrypting contents of '{0}' using {1} cipher".format(source, method))
+            output_text = decrypt_caesar(input_text)
+
+        # Viginere ciphere decryption
+        elif decrypt_choice == "V":
+            passkey = input("Passkey? ")
+            while not passkey or len(passkey) < 1:
+                passkey = input("Please enter a valid passkey? ")            
+            print("Decrypting contents of '{0}' using {1} cipher with passkey {2}".format(source, method, passkey))
+            ouptut_text = decrypt_viginere(input_text, passkey)
+
+        # railcence cipher decryption
+        else:
+            num_rails = int(input("How many (positive integer) rails? "))
+            while not num_rails or num_rails < 1:
+                num_rails = input("How many (positive integer) rails? ")            
+            print("Decrypting contents of '{0}' using {1} cipher".format(source, method, num_rails))
+            output_text = decrypt_railfence(input_text, num_rails)
+
+    # get output format
+    print("...\n*Output*")
+    output_choice = input("(F)ile or (S)tring? ").upper()
+    while not output_choice or output_choice[0] not in ['F', 'S']:
+        output_choice = input("Please enter either 'F' for file or 'S' for string. Again (F/S)? ").upper()
+
+    # file output
+    if output_choice[0] == "F":
+        filename = input("Filename? ")
+        print("Writing ciphertext to '{0}'".format(filename))
+        while not filename or len(filename) < 1:
+            filename = input("Please enter a valid non-empty filename. ")
+        with open(filename, "w") as output_file:
+            output_file.write(output_text)
+
+    # string output
+    else:
+        print("The output is is: {0}".format(output_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()

jamesc4-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?
+
+
+
+
+

jamesc4-assign1/railfence-cipher.txt

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+WECRLTEERDSOEEFEAOCAIVDEN

jamesc4-assign1/railfence-plain.txt

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+WE ARE DISCOVERED. FLEE AT ONCE