added submission for sandips

sandips-assign1/SandipAssignment1.py

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+"""
+Assignment 1: Cryptography
+Course: CS 92SI
+Name: SANDIP SRINIVAS
+Date: 7 OCTOBER 2015
+
+This program implements multiple cryptography types: caesar, vigniere, and Railfence.
+The program gives the user the option of encrypting/decrypting into a file or string,
+and gives output accordingly.
+"""
+
+def encrypt_caesar(plaintext):
+    mapping = {}
+    for number in range(97, 122):
+        if (number < 120):
+            mapping[chr(number)] = chr(number + 3)
+        else:
+            mapping[chr(number)] = chr(97 + (number - 120))
+    ciphertext = ""
+    for letter in plaintext:
+        ciphertext += mapping[letter]
+    return ciphertext
+
+def decrypt_caesar(ciphertext):
+    mapping = {}
+    for number in range(97, 122):
+        if (number > 100):
+            mapping[chr(number)] = chr(number - 3)
+        else:
+            mapping[chr(number)] = chr(122 - (99 - number))
+    plaintext = ""
+    for letter in ciphertext:
+            plaintext += mapping[letter]
+    return plaintext
+
+
+def encrypt_vigenere(plaintext, keyword):
+    mapping = {}
+    for number in range(1, 26):
+        mapping[chr(number + 96)] = number
+    ciphertext = ""
+    for index in range(0, len(plaintext)):
+        ciphertext += chr(((mapping[plaintext[index]] + mapping[keyword[index]]) % 26) + 95)
+    return ciphertext
+
+
+def decrypt_vigenere(ciphertext, keyword):
+    print(ciphertext)
+    print(keyword)
+    mapping = {}
+    for number in range(1, 26):
+        mapping[chr(number + 96)] = number
+    plaintext = ""
+    for index in range(0, len(ciphertext)):
+        if (mapping[ciphertext[index]] >= mapping[keyword[index]]):
+            plaintext += chr(mapping[ciphertext[index]] - mapping[keyword[index]] + 97)
+        else:
+            plaintext += chr(27 - abs(mapping[ciphertext[index]] - mapping[keyword[index]]) + 96)
+    return plaintext
+
+
+def encrypt_railfence(plaintext, num_rails):
+    ciphertext = ""
+    indexAdjust = 2
+    for rail in range(1, num_rails + 1):
+        index = rail - 1  
+        if (rail == 1 or rail == num_rails):
+            ciphertext += plaintext[rail-1:len(plaintext):2*(num_rails -1)]
+        else:
+            ciphertext += plaintext[rail - 1]
+            while (index < len(plaintext) - 1):
+                index += ((2*(num_rails -1)))
+                if (num_rails != 3): index -= indexAdjust
+                if (    index < len(plaintext) - 1):
+                    ciphertext += plaintext[index]               
+                    index += ((2*(num_rails -1)) - indexAdjust + 2)
+                    if (index < len(plaintext) - 1):
+                        ciphertext += plaintext[index]
+            indexAdjust += 2
+    return ciphertext
+
+def decrypt_railfence(ciphertext, num_rails):
+    plaintext = ciphertext[0]
+    index = 0
+    adjust1 = 0
+    while (len(plaintext) < len(ciphertext)):
+        index += (int)(len(ciphertext) / num_rails) - 1 + adjust1
+        if (index < len(ciphertext)):
+            plaintext += ciphertext[index]
+            index += (int)(len(ciphertext) / (num_rails - 1)) - adjust1
+            if (index < len(ciphertext)):
+                plaintext += ciphertext[index]
+                index -= (int)(len(ciphertext) / (num_rails - 1)) - adjust1 - 1
+                if (index < len(ciphertext)):
+                    plaintext += ciphertext[index]
+                    index -= (int)(len(ciphertext) / num_rails) - 1 + adjust1
+                    if (index < len(ciphertext)):
+                        plaintext += ciphertext[index]
+                        ++adjust1
+
+    print(plaintext)
+
+
+def read_from_file(filename):
+    with open(filename, 'r') as f:
+        content = f.read()
+    return str(content)
+
+
+def write_to_file(filename, content):
+     with open(filename, 'w') as f:
+        f.write(content)
+
+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*")
+    fileOrString = input("(F)ile or (S)tring? ")
+    fileOrString = fileOrString.lower()
+    while (not fileOrString.isalpha() or len(fileOrString) != 1 or 
+        fileOrString not in ['f', 's']):
+            fileOrString = input("Please enter either an F for File or an S for String: ")
+            fileOrString = fileOrString.lower()
+    if (fileOrString == 'f'):
+        filename = input("Filename? ")
+        name = read_from_file(filename)
+    else: 
+        name = input("Enter the string to encrypt: ")
+
+    print("*Transform*")
+    encryptOrDecrypt = input("(E)ncrypt or (D)ecrypt? ")
+    encryptOrDecrypt = encryptOrDecrypt.lower()
+    while (not encryptOrDecrypt.isalpha() or len(encryptOrDecrypt) != 1 or 
+        encryptOrDecrypt not in ['e', 'd']):
+            encryptOrDecrypt = input("Please enter either an E for Encrypt or an D for Decrypt: ")
+            encryptOrDecrypt = encryptOrDecrypt.lower()
+
+    cipherType = input("(C)aesar, (V)igenere, or (R)ailfence? ")
+    cipherType = cipherType.lower()
+    while (not cipherType.isalpha() or len(cipherType) != 1 or
+        cipherType not in ['c', 'v', 'r']): 
+            cipherType = input("Please enter either a C for Caesar, V for Vigniere, or R for Railfence: ")
+            cipherType = cipherType.lower()
+
+    if (cipherType == 'c'):
+        if (encryptOrDecrypt == 'e'):
+            print("Encrypting", name, "using Caesar cipher")
+            output = encrypt_caesar(name.lower())
+        if (encryptOrDecrypt == 'd'):
+            print("Decrypting", name, "using Caesar cipher")
+            output = decrypt_caesar(name.lower())
+
+    if (cipherType == 'v'):
+        passkey = input("Passkey? ")
+        while (not passkey.isalpha()):
+            passkey = input("Please enter a passkey of only English letters: ")
+        if len(passkey) < len(name): 
+            difference = len(name) - len(passkey)
+            for index in range(0, difference):
+                passkey += passkey[index%len(name)]
+        if len(passkey) > len(name):
+            passkey = passkey[:len(name)-1]
+        if (encryptOrDecrypt == 'e'):
+            print("Encrypting", name, "using Vigniere cypher with key", passkey)
+            output = encrypt_vigenere(name.lower(), passkey.lower())
+        if (encryptOrDecrypt == 'd'):
+            print("Decrypting", name, "using Vigniere cypher with key", passkey)
+            output = decrypt_vigenere(name.lower(), passkey.lower())
+
+    if (cipherType == 'r'):
+        rails = input("Enter number of rails: ")
+        while (not rails.isnumeric):
+            rails  = input("Please enter a positive integer number of rails: ")
+        if (encryptOrDecrypt == 'e'): 
+            print("Encrypting", name, "using Railfence cipher with", rails, "rails")
+            output = encrypt_railfence(name, int(rails))
+        if (encryptOrDecrypt == 'd'):
+            print("Decrypting", name, "using Railfence cipher with", rails, "rails")
+            output = decrypt_railfence(name, int(rails))
+
+    print("*Output*")
+    fileOrString = input("(F)ile or (S)tring? ")
+    fileOrString = fileOrString.lower()
+    while (not fileOrString.isalpha() or len(fileOrString) != 1 or 
+        fileOrString not in ['f', 's']):
+            fileOrString = input("Please enter either an F for File or an S for String: ")
+            fileOrString = fileOrString.lower()
+    if (fileOrString == 'f'): name = input("Filename? ")
+    else: print(output)  # Print or write the transformed 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()

sandips-assign1/feedback.txt

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+Name: Sandip Srinivas
+1) How long did this assignment take you to complete?
+Roughly 5 hours
+
+
+2) What has been the best part of the class so far?
+Doing practice problems in class (anagrams, cyclone phrases, etc)
+
+
+
+
+3) What can we do to make this class more enjoyable for you?
+Teach more cool python specific things
+
+
+
+
+4) What types of assignments would excite you in this class?
+Games (i.e. brick breaker, boggle, but not as time consuming as boggle)
+
+
+
+