Create app.py

app.py

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+import streamlit as st
+import base64
+from Crypto.Cipher import AES
+from Crypto.Util.Padding import pad, unpad
+from Crypto.Random import get_random_bytes
+import hashlib
+
+st.title("🔒 Text Encryptor/Decryptor")
+st.markdown("Secure text encryption using multiple algorithms")
+
+# Encryption functions
+def caesar_encrypt(text, shift):
+    result = ""
+    for char in text:
+        if char.isalpha():
+            ascii_offset = 65 if char.isupper() else 97
+            result += chr((ord(char) + shift - ascii_offset) % 26 + ascii_offset)
+        else:
+            result += char
+    return result
+
+def caesar_decrypt(text, shift):
+    return caesar_encrypt(text, -shift)
+
+def vigenere_encrypt(text, key):
+    key = key.upper()
+    key_len = len(key)
+    encrypted = []
+    for i, char in enumerate(text):
+        if char.isalpha():
+            offset = 65 if char.isupper() else 97
+            key_char = key[i % key_len]
+            shift = ord(key_char) - 65
+            encrypted_char = chr((ord(char) + shift - offset) % 26 + offset)
+            encrypted.append(encrypted_char)
+        else:
+            encrypted.append(char)
+    return "".join(encrypted)
+
+def vigenere_decrypt(text, key):
+    key = key.upper()
+    key_len = len(key)
+    decrypted = []
+    for i, char in enumerate(text):
+        if char.isalpha():
+            offset = 65 if char.isupper() else 97
+            key_char = key[i % key_len]
+            shift = ord(key_char) - 65
+            decrypted_char = chr((ord(char) - shift - offset) % 26 + offset)
+            decrypted.append(decrypted_char)
+        else:
+            decrypted.append(char)
+    return "".join(decrypted)
+
+def aes_encrypt(text, password):
+    salt = get_random_bytes(16)
+    key = hashlib.scrypt(password.encode(), salt=salt, n=16384, r=8, p=1, dklen=32)
+    iv = get_random_bytes(16)
+    cipher = AES.new(key, AES.MODE_CBC, iv)
+    ciphertext = cipher.encrypt(pad(text.encode(), AES.block_size))
+    return base64.b64encode(salt + iv + ciphertext).decode()
+
+def aes_decrypt(encrypted, password):
+    encrypted = base64.b64decode(encrypted)
+    salt = encrypted[:16]
+    iv = encrypted[16:32]
+    ciphertext = encrypted[32:]
+    key = hashlib.scrypt(password.encode(), salt=salt, n=16384, r=8, p=1, dklen=32)
+    cipher = AES.new(key, AES.MODE_CBC, iv)
+    decrypted = unpad(cipher.decrypt(ciphertext), AES.block_size)
+    return decrypted.decode()
+
+# Interface
+operation = st.radio("Select Operation:", ["Encrypt", "Decrypt"])
+method = st.selectbox("Select Encryption Method:", 
+                     ["Caesar Cipher", "Vigenère Cipher", "AES-256"])
+
+text = st.text_area("Enter Text:", height=200)
+password = st.text_input("Enter Key/Password:", type="password")
+
+if st.button(f"Perform {operation}"):
+    if text and password:
+        try:
+            if method == "Caesar Cipher":
+                if not password.isdigit():
+                    raise ValueError("Caesar cipher requires numeric key")
+                shift = int(password) % 26
+                if operation == "Encrypt":
+                    result = caesar_encrypt(text, shift)
+                else:
+                    result = caesar_decrypt(text, shift)
+                    
+            elif method == "Vigenère Cipher":
+                if operation == "Encrypt":
+                    result = vigenere_encrypt(text, password)
+                else:
+                    result = vigenere_decrypt(text, password)
+                    
+            elif method == "AES-256":
+                if operation == "Encrypt":
+                    result = aes_encrypt(text, password)
+                else:
+                    result = aes_decrypt(text, password)
+                    
+            st.success(f"Result:")
+            st.code(result)
+            
+            st.download_button(
+                label="Download Result",
+                data=result,
+                file_name="encrypted.txt" if operation == "Encrypt" else "decrypted.txt",
+                mime="text/plain"
+            )
+            
+        except Exception as e:
+            st.error(f"Error: {str(e)}")
+    else:
+        st.warning("Please enter both text and key/password")
+
+st.sidebar.markdown("## Instructions")
+st.sidebar.markdown("""
+1. Select encrypt/decrypt operation
+2. Choose encryption method
+3. Enter text and key/password
+4. Click the action button
+                    
+**Key Requirements:**
+- Caesar: Numeric key (1-25)
+- Vigenère: Text key (letters only)
+- AES-256: Strong password (any characters)
+""")