Homework01

homework01/caesar.py

@@ -2,39 +2,39 @@
 
 
 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
+    if shift < 0:
+        shift = 26 + shift
+    a = []
+    for i in range(len(plaintext)):
+        if plaintext[i].isalpha():
+            a.append(ord(plaintext[i]))
+        else:
+            a.append(ord(plaintext[i]) - shift)
+    for i in range(len(a)):
+        temp = a[i] + shift
+        if plaintext[i].isalpha():
+            if a[i] >= ord("a") and a[i] <= ord("z"):
+                # Маленькие буквы
+                if temp > ord("z"):
+                    a[i] = shift - (ord("z") - a[i]) + ord("a") - 1
+                else:
+                    a[i] = a[i] + shift
+            else:
+                # Большие буквы
+                if temp > ord("Z"):
+                    a[i] = shift - (ord("Z") - a[i]) + ord("A") - 1
+                else:
+                    a[i] = a[i] + shift
+        else:
+            a[i] = a[i] + shift
+    for i in range(len(a)):
+        ciphertext += chr(a[i])
     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:

homework01/rsa.py

@@ -3,69 +3,55 @@
 
 
 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
+    if n == 1:
+        return False
+    for i in range(2, n - 1):
+        if n % i == 0:
+            return False
+    return True
 
 
 def gcd(a: int, b: int) -> int:
-    """
-    Euclid's algorithm for determining the greatest common divisor.
+    if a == 0 or b == 0:
+        return max(a, b)
+    max_del = 1
+    for i in range(1, min(a, b)):
+        if a % i == 0 and b % i == 0 and i > max_del:
+            max_del = i
+    return max_del
 
-    >>> gcd(12, 15)
-    3
-    >>> gcd(3, 7)
-    1
-    """
-    # PUT YOUR CODE HERE
-    pass
 
+def extended_gcd(a: int, b: int):
+    if a == 0:
+        return (b, 0, 1)
+    temp = extended_gcd(b % a, a)
+    return (temp[0], temp[2] - (b // a) * temp[1], temp[1])
 
-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(e: int, phi: int) -> int:
+    gcd_res = extended_gcd(e, phi)
+    if gcd_res[1] >= 0:
+        return gcd_res[1]
+    else:
+        return gcd_res[1] + max(e, phi)
 
 
 def generate_keypair(p: int, q: int) -> tp.Tuple[tp.Tuple[int, int], tp.Tuple[int, int]]:
     if not (is_prime(p) and is_prime(q)):
         raise ValueError("Both numbers must be prime.")
     elif p == q:
         raise ValueError("p and q cannot be equal")
-
-    # n = pq
-    # PUT YOUR CODE HERE
-
-    # phi = (p-1)(q-1)
-    # PUT YOUR CODE HERE
-
+    n = p * q
+    phi = (p - 1) * (q - 1)
     # Choose an integer e such that e and phi(n) are coprime
     e = random.randrange(1, phi)
-
     # Use Euclid's Algorithm to verify that e and phi(n) are coprime
     g = gcd(e, phi)
     while g != 1:
         e = random.randrange(1, phi)
         g = gcd(e, phi)
-
     # Use Extended Euclid's Algorithm to generate the private key
     d = multiplicative_inverse(e, phi)
-
     # Return public and private keypair
     # Public key is (e, n) and private key is (d, n)
     return ((e, n), (d, n))
@@ -85,7 +71,7 @@ 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 +1,64 @@
 def encrypt_vigenere(plaintext: str, keyword: str) -> str:
-    """
-    Encrypts plaintext using a Vigenere cipher.
-
-    >>> encrypt_vigenere("PYTHON", "A")
-    'PYTHON'
-    >>> encrypt_vigenere("python", "a")
-    'python'
-    >>> encrypt_vigenere("ATTACKATDAWN", "LEMON")
-    'LXFOPVEFRNHR'
-    """
     ciphertext = ""
-    # PUT YOUR CODE HERE
+
+    for i in range(len(plaintext)):
+        l = ord(plaintext[i])
+        shift = ord(keyword[i % len(keyword)])  # смещене
+
+        k = ord(keyword[i % len(keyword)])  # порядковый номер, A-Z, a-z
+        if k >= ord("a") and k <= ord("z"):
+            shift -= ord("a")
+        else:
+            shift -= ord("A")
+
+        if plaintext[i].isalpha():
+            if l >= ord("a") and l <= ord("z"):
+                temp = l + shift
+                if temp > ord("z"):
+                    ciphertext += chr(shift - (ord("z") - l) + ord("a") - 1)
+                else:
+                    ciphertext += chr(temp)
+            else:
+                temp = l + shift
+                if temp > ord("Z"):
+                    ciphertext += chr(shift - (ord("Z") - l) + ord("A") - 1)
+                else:
+                    ciphertext += chr(temp)
+        else:
+            ciphertext += plaintext[i]
+
     return 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
+    ciphertexttext = ""
+
+    for i in range(len(ciphertext)):
+        l = ord(ciphertext[i])
+        shift = ord(keyword[i % len(keyword)])
+
+        k = ord(keyword[i % len(keyword)])
+        if k >= ord("a") and k <= ord("z"):
+            shift -= ord("a")
+        else:
+            shift -= ord("A")
+
+        shift = 26 - shift
+
+        if ciphertext[i].isalpha():
+            if l >= ord("a") and l <= ord("z"):
+                temp = l + shift
+                if temp > ord("z"):
+                    ciphertexttext += chr(shift - (ord("z") - l) + ord("a") - 1)
+                else:
+                    ciphertexttext += chr(temp)
+            else:
+                temp = l + shift
+                if temp > ord("Z"):
+                    ciphertexttext += chr(shift - (ord("Z") - l) + ord("A") - 1)
+                else:
+                    ciphertexttext += chr(temp)
+        else:
+            ciphertexttext += ciphertext[i]
+
+    return ciphertexttext