added submission for da6462

da6462-assign1/crypto.py

@@ -0,0 +1,258 @@
+"""
+Assignment 1: Cryptography
+Course: CS 92SI
+Name: <YOUR NAME>
+Date: <DATE>
+
+Replace this with a description of the program.
+"""
+
+def encrypt_caesar(plaintext):
+    """
+    Encrypts plaintext using a Caesar cipher.
+    Add more implementation details here.
+    """
+    encrypt = []
+    for i in plaintext.upper():
+        c = ord(i) + 3
+        if c > 90:
+            encrypt.append(chr(c - 26))
+        else:
+            encrypt.append(chr(c))
+    return "".join(encrypt)
+
+def decrypt_caesar(ciphertext):
+    """
+    Decrypts a ciphertext using a Caesar cipher.
+    Add more implementation details here.
+    """
+    decrypt = []
+    for i in ciphertext.upper():
+        c = ord(i) - 3
+        if c < 65:
+            decrypt.append(chr(c + 26))
+        else:
+            decrypt.append(chr(c))
+    return "".join(decrypt)
+
+def encrypt_vigenere(plaintext, keyword):
+    """
+    Encrypts plaintext using a Vigenere cipher with a keyword.
+    Add more implementation details here.
+    """
+    keyword = (keyword *((len(plaintext) / len(keyword)) + 1)).upper()
+    keyword = keyword[: len(plaintext)]
+    final = []
+    for i, c in enumerate(plaintext.upper()):
+        letter = ord(c) + ord(keyword[i])
+        while letter > 90 or letter < 65:
+            temp = letter % 91
+            temp = letter % 26
+            letter = 65 + temp
+        final.append(chr(letter))
+    return "".join(final)
+
+def decrypt_vigenere(ciphertext, keyword):
+    """
+    Decrypts ciphertext using a Vigenere cipher with a keyword.
+    Add more implementation details here.
+    """
+    keyword = (keyword *((len(ciphertext) / len(keyword)) + 1)).upper()
+    keyword = keyword[: len(ciphertext)]
+    final = []
+    for i, c in enumerate(ciphertext.upper()):
+        letter = ord(c) - ord(keyword[i])
+        while letter > 90 or letter < 65:
+            temp = letter % 91
+            temp = letter % 26
+            letter = 65 + temp
+        final.append(chr(letter))
+    return "".join(final)
+
+def encrypt_railfence(plaintext, num_rails):
+    """
+    Encrypts plaintext using a railfence cipher.
+    Add more implementation details here.
+    """
+    total_chr = len(plaintext)
+    direction = 1
+    zig_zag = [""] *num_rails
+    rail = 0
+    i = 0
+    while total_chr > 0:
+        zig_zag[rail] += plaintext[i]
+        total_chr -= 1
+        if rail == num_rails - 1 and direction == 1:
+            direction *= -1
+        if rail == 0 and direction == -1:
+            direction *= -1
+        rail += direction
+        i += 1
+    return "".join(zig_zag)
+
+def decrypt_railfence(ciphertext, num_rails):
+    """
+    Encrypts plaintext using a railfence cipher.
+    Add more implementation details here.
+    """
+    if num_rails == 1:
+        return ciphertext
+    l = []
+    num_segments = len(ciphertext) / (num_rails - 1)
+    last_segment = len(ciphertext) % (num_rails - 1)
+    if last_segment == 0:
+        total_segment = num_segments
+    else:
+        total_segment = num_segments + 1
+
+    num_per_rail = [0] * num_rails
+
+    #num_per_rail gives you the number of characters per rail
+
+    for i in range(1, total_segment+1):
+        if i % 2 != 0:
+            num_per_rail[0] += 1
+    num_per_rail[-1] = total_segment - num_per_rail[0]
+
+    for i in range(1, num_rails - 1):
+        num_per_rail[i] = (len(ciphertext) - num_per_rail[-1] - num_per_rail[0]) / (num_rails - 2)
+    if last_segment != 0:
+        extra = (len(ciphertext) - num_per_rail[-1] - num_per_rail[0]) % (num_rails - 2)
+        if total_segment % 2 == 0:
+            for i in range(num_rails - 2, 0, -1):
+                if extra > 0:
+                    num_per_rail[i] += 1
+                    extra -= 1
+        else:
+            for i in range(1, num_rails - 1):
+                if extra > 0:
+                    num_per_rail[i] += 1
+                    extra -= 1
+    total_chr = len(ciphertext)
+    direction = 1
+    curr_rail = 0
+    curr_index = 0
+    while total_chr > 0:
+        l.append(ciphertext[curr_index])
+        total_chr -= 1
+        if curr_rail == num_rails - 1 and direction == 1:
+            direction *= -1
+            num_per_rail[-2] -= 1
+        if curr_rail == 0 and direction == -1:
+            direction *= -1
+            num_per_rail[0] += 1
+
+        if direction == 1:
+            curr_index += num_per_rail[curr_rail]
+        else:
+            curr_index -= num_per_rail[curr_rail - 1]
+        curr_rail += direction
+    return "".join(l)
+
+def read_from_file(filename):
+    """
+    Reads and returns content from a file.
+    Add more implementation details here.
+    """
+    f = open(filename, 'r')
+    return f.read()
+
+
+def write_to_file(filename, content):
+    """
+    Writes content to a file.
+    Add more implementation details here.
+    """
+    f = open(filename, 'w')
+    f.write(content)
+
+
+def strip_string(usr_input):
+    '''
+    Strips all non-alphabetic characters and returns
+    new string
+    '''
+    return "".join([i for i in usr_input.upper() if ord(i) < 91 and ord(i) > 64])
+
+
+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*")
+    a = input("(F)ile or (S)tring? ").upper()
+    while not a or a[0] not in ['F', 'S']:
+        a = input("Please enter either (F)ile or (S)tring ")
+    if a == "F":
+        fn = input("Filename: ")
+        usr_input = strip_string(read_from_file(fn))
+    else:
+        usr_input = strip_string(input("Enter the string to encrypt: "))
+
+    print("*Transform*")
+    b = input("(E)ncrpyt or (D)ecrpyt? ").upper()
+    while not b or b not in ['E', 'D']:
+        b = input("Please enter either (E)ncrypt or (D)ecrypt")
+    c = input("(C)aesar, (V)igenere, or (R)ailfence? ").upper()
+    while not c or c not in ['C', 'V', 'R']:
+        c = input("Please enter either (C)aesar, (V)igenere, or (R)ailfence")
+
+    if c == "C":
+        if b == 'E':
+            final_output = encrypt_caesar(usr_input)
+        else:
+            final_output = decrypt_caesar(usr_input)
+    elif c == "V":
+        if b == 'E':
+            key = input("Passkey? ")
+            final_output = encrypt_vigenere(usr_input, key)
+        else:
+            key = input("Passkey? ")
+            final_output = decrypt_vigenere(usr_input, key)
+    else:
+        if b == 'E':
+            rails = input('Number of rails? ')
+            final_output = encrypt_railfence(usr_input, rails)
+        else:
+            rails = input('Number of rails? ')
+            final_output = decrypt_railfence(usr_input, rails)
+    print("*Output*")
+    d = input("(F)ile or (S)tring? ").upper()
+    while not d or d[0] not in ['F', 'S']:
+        d = input("Please enter either (F)ile or (S)tring ")
+    if d == "S":
+        print final_output
+    else:
+        fn = input("Enter the file name")
+        write_to_file(fn, final_output)
+
+# 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()

da6462-assign1/feedback.txt

@@ -0,0 +1,26 @@
+Name: <David Park>
+1) How long did this assignment take you to complete?
+7 hours
+
+
+2) What has been the best part of the class so far?
+The interactive labs
+
+
+
+
+3) What can we do to make this class more enjoyable for you?
+This homework felt like a bit of harsh ramp in difficulty, especially the
+railfence cipher. I couldn't quite get the algorithm down, and implementing it
+using slices and list comprehension would have made it much more confusing for
+me.
+
+
+
+
+4) What types of assignments would excite you in this class?
+More projects like these, but maybe a bit more guidance?
+
+
+
+