Homework01

homework00/hello.py

@@ -1,5 +1,5 @@
 def get_greeting(name: str) -> str:
-    pass
+    return f"Hello, {name}!"
 
 
 if __name__ == "__main__":

homework01/caesar.py

@@ -1,46 +1,28 @@
 import typing as tp
+from string import ascii_lowercase as lower
+from string import ascii_uppercase as upper
 
 
 def encrypt_caesar(plaintext: str, shift: int = 3) -> str:
-    """
-    Encrypts plaintext using a Caesar cipher.
-
-    >>> encrypt_caesar("PYTHON")
-    'SBWKRQ'
-    >>> encrypt_caesar("python")
-    'sbwkrq'
-    >>> encrypt_caesar("Python3.6")
-    'Sbwkrq3.6'
-    >>> encrypt_caesar("")
-    ''
-    """
     ciphertext = ""
-    # PUT YOUR CODE HERE
+    for char in plaintext:
+        if char.isalpha():
+            if char.islower():
+                char = lower[(lower.index(char) + shift) % 26]
+            else:
+                char = upper[(upper.index(char) + shift) % 26]
+        ciphertext += char
     return ciphertext
 
 
 def decrypt_caesar(ciphertext: str, shift: int = 3) -> str:
-    """
-    Decrypts a ciphertext using a Caesar cipher.
-
-    >>> decrypt_caesar("SBWKRQ")
-    'PYTHON'
-    >>> decrypt_caesar("sbwkrq")
-    'python'
-    >>> decrypt_caesar("Sbwkrq3.6")
-    'Python3.6'
-    >>> decrypt_caesar("")
-    ''
-    """
-    plaintext = ""
-    # PUT YOUR CODE HERE
-    return plaintext
+    return encrypt_caesar(ciphertext, -shift)
 
 
 def caesar_breaker_brute_force(ciphertext: str, dictionary: tp.Set[str]) -> int:
-    """
-    Brute force breaking a Caesar cipher.
-    """
     best_shift = 0
-    # PUT YOUR CODE HERE
+    for shift in range(26):
+        decrypted_msg = decrypt_caesar(ciphertext, shift)
+        if decrypted_msg in dictionary:
+            best_shift = shift
     return best_shift

homework01/rsa.py

@@ -3,43 +3,32 @@
 
 
 def is_prime(n: int) -> bool:
-    """
-    Tests to see if a number is prime.
-
-    >>> is_prime(2)
-    True
-    >>> is_prime(11)
-    True
-    >>> is_prime(8)
-    False
-    """
-    # PUT YOUR CODE HERE
-    pass
+    for div in range(2, int(n**0.5) + 1):
+        if n % div == 0:
+            return False
+    return n != 1
 
 
 def gcd(a: int, b: int) -> int:
-    """
-    Euclid's algorithm for determining the greatest common divisor.
+    if b == 0:
+        return a
+    return gcd(b, a % b)
 
-    >>> gcd(12, 15)
-    3
-    >>> gcd(3, 7)
-    1
-    """
-    # PUT YOUR CODE HERE
-    pass
 
+def gcdex(a, b):
+    if b == 0:
+        return a, 1, 0
+    else:
+        d, x, y = gcdex(b, a % b)
+        return d, y, x - y * (a // b)
 
-def multiplicative_inverse(e: int, phi: int) -> int:
-    """
-    Euclid's extended algorithm for finding the multiplicative
-    inverse of two numbers.
 
-    >>> multiplicative_inverse(7, 40)
-    23
-    """
-    # PUT YOUR CODE HERE
-    pass
+def multiplicative_inverse(a: int, n: int) -> int:
+    d, x, y = gcdex(a, n)
+    if d == 1:
+        return (x % n + n) % n
+    else:
+        return 0
 
 
 def generate_keypair(p: int, q: int) -> tp.Tuple[tp.Tuple[int, int], tp.Tuple[int, int]]:
@@ -49,10 +38,10 @@ def generate_keypair(p: int, q: int) -> tp.Tuple[tp.Tuple[int, int], tp.Tuple[in
         raise ValueError("p and q cannot be equal")
 
     # n = pq
-    # PUT YOUR CODE HERE
+    n = p * q
 
     # phi = (p-1)(q-1)
-    # PUT YOUR CODE HERE
+    phi = (p - 1) * (q - 1)
 
     # Choose an integer e such that e and phi(n) are coprime
     e = random.randrange(1, phi)
@@ -85,7 +74,7 @@ def decrypt(pk: tp.Tuple[int, int], ciphertext: tp.List[int]) -> str:
     # Unpack the key into its components
     key, n = pk
     # Generate the plaintext based on the ciphertext and key using a^b mod m
-    plain = [chr((char ** key) % n) for char in ciphertext]
+    plain = [chr((char**key) % n) for char in ciphertext]
     # Return the array of bytes as a string
     return "".join(plain)
 

homework01/vigenere.py

@@ -1,30 +1,18 @@
-def encrypt_vigenere(plaintext: str, keyword: str) -> str:
-    """
-    Encrypts plaintext using a Vigenere cipher.
+from caesar import decrypt_caesar, encrypt_caesar
 
-    >>> encrypt_vigenere("PYTHON", "A")
-    'PYTHON'
-    >>> encrypt_vigenere("python", "a")
-    'python'
-    >>> encrypt_vigenere("ATTACKATDAWN", "LEMON")
-    'LXFOPVEFRNHR'
-    """
-    ciphertext = ""
-    # PUT YOUR CODE HERE
-    return ciphertext
 
+def encrypt_vigenere(plaintext: str, keyword: str, encode: bool = True) -> str:
+    ciphertext = []
+    for index, char in enumerate(plaintext.lower()):
+        shift = ord(keyword[index % len(keyword)].lower()) - 97
+        if encode:
+            ciphertext.append(encrypt_caesar(char, shift))
+        else:
+            ciphertext.append(decrypt_caesar(char, shift))
+        if plaintext[index].isupper():
+            ciphertext[-1] = ciphertext[-1].upper()
+    return "".join(ciphertext)
 
-def decrypt_vigenere(ciphertext: str, keyword: str) -> str:
-    """
-    Decrypts a ciphertext using a Vigenere cipher.
 
-    >>> decrypt_vigenere("PYTHON", "A")
-    'PYTHON'
-    >>> decrypt_vigenere("python", "a")
-    'python'
-    >>> decrypt_vigenere("LXFOPVEFRNHR", "LEMON")
-    'ATTACKATDAWN'
-    """
-    plaintext = ""
-    # PUT YOUR CODE HERE
-    return plaintext
+def decrypt_vigenere(ciphertext: str, keyword: str) -> str:
+    return encrypt_vigenere(ciphertext, keyword, encode=False)