added submission for quint

quint-assign1/quint-assign1.py

@@ -0,0 +1,218 @@
+"""
+Assignment 1: Cryptography
+Course: CS 92SI
+Name: Quint Underwood
+Date: 9 October 2015
+
+Replace this with a description of the program.
+"""
+
+def encrypt_caesar(plaintext):
+    """
+    Encrypts plaintext using a Caesar cipher.
+    Add more implementation details here.
+    """
+    shift = int(input("By how many letters do you want to shift? "))
+    encoded_phrase = ""
+    for letter in plaintext:
+        letter = chr(ord(letter) + shift)
+        if letter > 'z':
+            letter = chr(ord(letter) - 26)
+        encoded_phrase += letter
+    #print(encoded_phrase.upper())
+    return(encoded_phrase.upper())
+
+
+def decrypt_caesar(ciphertext):
+    """
+    Decrypts a ciphertext using a Caesar cipher.
+    Add more implementation details here.
+    """
+    shift = int(input("How many letters was this phrase shifted when it was encoded? "))
+    decoded_phrase = ""
+    for letter in ciphertext:
+        letter = chr(ord(letter) - shift)
+        if letter < 'a':
+            letter = chr(ord(letter) + 26)
+        decoded_phrase += letter
+    return(decoded_phrase.upper())
+
+def encrypt_vigenere(plaintext, keyword):
+    """
+    Encrypts plaintext using a Vigenere cipher with a keyword.
+    Add more implementation details here.
+    """
+    encoded_phrase = ""
+    length = len(keyword)
+    i=0
+    for letter in plaintext:
+        letter = chr(ord(letter) + ord(keyword[i%length]) - ord('a'))
+        if letter > 'z':
+            letter = chr(ord(letter) - 26)
+        encoded_phrase += letter
+        i += 1
+    return (encoded_phrase)
+
+
+
+def decrypt_vigenere(ciphertext, keyword):
+    """
+    Decrypts ciphertext using a Vigenere cipher with a keyword.
+    Add more implementation details here.
+    """
+    decoded_phrase = ""
+    length = len(keyword)
+    i=0
+    for letter in ciphertext:
+        letter = chr(ord(letter) - ord(keyword[i%length]) + ord('a'))
+        if letter < 'a':
+            letter = chr(ord(letter) + 26)
+        decoded_phrase += letter
+        i += 1
+    return (decoded_phrase)
+
+
+def encrypt_railfence(plaintext, num_rails):
+    """
+    Encrypts plaintext using a railfence cipher.
+    Add more implementation details here.
+    """
+    divisor = 2 * num_rails - 2
+    encoded_phrase = ""
+    rails = [[letter for n, letter in enumerate(plaintext) if ((n+i) % divisor == 0 or (n-i) % divisor == 0)] for i in range(num_rails)]
+    for rail in rails:
+        for element in rail:
+            encoded_phrase += element
+    return(encoded_phrase)
+
+def decrypt_railfence(ciphertext, num_rails):
+    """
+    Encrypts plaintext using a railfence cipher.
+    Add more implementation details here.
+    """
+
+    divisor = 2 * num_rails - 2
+    print("divisor= ", divisor)
+    length = len(ciphertext)
+    decoded_phrase = [None]*length
+    print(decoded_phrase)
+    print ("ciphertext length=", length)
+    rail_length = [length//divisor + 1 if (i < (num_rails - 1) and i > 0) else (length//divisor) for i in range(num_rails)]
+
+    print (rail_length)
+
+    for i in range(length % divisor):
+        if i < num_rails - 1:
+            rail_length[i] += 1
+        else:
+            rail_length[num_rails-1 - (i % (divisor//2))] += 1
+
+    print (rail_length)
+
+    n=0
+    for i in range(num_rails):
+        decoded_phrase[i]=ciphertext[n]
+        n+=1
+        print("i loop n: ",n)
+        for j in range(rail_length[i]-2):
+            print("small", (j+1)*divisor-i)
+            print("j loop n: ", n)
+            decoded_phrase[(j+1)*divisor-i] = ciphertext[n]
+            if (j+1)*divisor+1 < len(ciphertext)-1:
+                print("big", (j+1)*divisor+1)
+                decoded_phrase[(j+1)*divisor+i] = ciphertext[n+1]
+                n+=1
+                print("if loop n: ",n)
+            n+=1
+    return(decoded_phrase)
+
+
+
+def read_from_file(filename):
+    """
+    Reads and returns content from a file.
+    Add more implementation details here.
+    """
+    pass  # Your implementation here
+
+
+
+def write_to_file(filename, content):
+    """
+    Writes content to a file.
+    Add more implementation details here.
+    """
+    pass  # Your implementation here
+
+
+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_method = input("(F)ile or (S)tring? ")
+    if input_method == 'S' or 's':
+        text = input("Enter the string to encrypt/decrypt: ").lower()
+    elif input_method == 'F' or 'f':
+        file_path = input("Please enter a file name: ")
+        with open(file_path, 'r') as f:
+            text = f.read()
+    else:
+        print("You did not enter in a correct input method.")
+
+    print("*Transform*")
+    direction = input("(E)ncrypt or (D)ecrypt? ").upper()
+    encrypt_type = input("(C)aesar, (V)igenere, or (R)ailfence? ").upper()
+
+    print("*Output*")
+    if direction == 'E':
+        if encrypt_type == 'C':
+            print(encrypt_caesar(text))
+        elif encrypt_type == 'V':
+            passkey = input("Passkey? ")
+            print(encrypt_vigenere(text, passkey))
+        else:
+            num_rails = int(input("Number of rails? "))
+            print(encrypt_railfence(text, num_rails))
+    else:
+        if encrypt_type == 'C':
+            print(decrypt_caesar(text))
+        elif encrypt_type == 'V':
+            passkey = input("Passkey? ")
+            print(decrypt_vigenere(text, passkey))
+        else:
+            num_rails = int(input("Number of rails? "))
+            print(decrypt_railfence(text, num_rails))
+
+
+
+# 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()