IS Lab

IS/Lab/Lab8/PKSE/pkse.py

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+import os
+import json
+import pickle
+from collections import defaultdict
+from phe import paillier
+
+# global keys
+public_key = None
+private_key = None
+
+
+def generate_keys():
+    global public_key, private_key
+    public_key, private_key = paillier.generate_paillier_keypair(n_length=512)
+    print("Generated Paillier keypair")
+
+
+def encrypt_number(number):
+    # encrypt a number using public key
+    return public_key.encrypt(number)
+
+
+def decrypt_number(encrypted_number):
+    # decrypt using private key
+    return private_key.decrypt(encrypted_number)
+
+
+def load_documents(docs_dir):
+    documents = {}
+    for filename in os.listdir(docs_dir):
+        if filename.endswith(".md"):
+            filepath = os.path.join(docs_dir, filename)
+            with open(filepath, "r") as f:
+                documents[filename] = f.read()
+    print(f"Loaded {len(documents)} documents")
+    return documents
+
+
+def build_inverted_index(documents):
+    # word -> list of doc IDs
+    inverted_index = defaultdict(set)
+    
+    for doc_id, content in documents.items():
+        words = content.lower().replace('\n', ' ').split()
+        words = [''.join(c for c in word if c.isalnum()) for word in words]
+        words = [w for w in words if w]
+        
+        for word in words:
+            inverted_index[word].add(doc_id)
+    
+    inverted_index = {word: list(doc_ids) for word, doc_ids in inverted_index.items()}
+    print(f"Built index with {len(inverted_index)} unique words")
+    return inverted_index
+
+
+def encrypt_index(inverted_index):
+    # encrypt index using Paillier
+    # for simplicity, we encrypt the hash of words and keep doc IDs in plaintext
+    # in production, you'd use more sophisticated techniques
+    encrypted_index = {}
+    
+    for word, doc_ids in inverted_index.items():
+        # create a numeric representation of the word
+        word_hash = hash(word) % (10**6)  # keep it manageable
+        encrypted_word = encrypt_number(word_hash)
+        encrypted_index[word] = {
+            'encrypted_hash': encrypted_word,
+            'doc_ids': doc_ids
+        }
+    
+    # save to file
+    with open("encrypted_index.pkl", "wb") as f:
+        pickle.dump(encrypted_index, f)
+    
+    print("Encrypted index saved")
+    return encrypted_index
+
+
+def decrypt_index(encrypted_index):
+    # decrypt index hashes
+    decrypted_index = {}
+    
+    for word, data in encrypted_index.items():
+        decrypted_hash = decrypt_number(data['encrypted_hash'])
+        decrypted_index[word] = {
+            'hash': decrypted_hash,
+            'doc_ids': data['doc_ids']
+        }
+    
+    return decrypted_index
+
+
+def encrypt_query(query):
+    # normalize and encrypt query
+    query = query.lower().strip()
+    query = ''.join(c for c in query if c.isalnum())
+    return query
+
+
+def search(query, encrypted_index, documents):
+    print(f"\nSearching for: '{query}'")
+    
+    # normalize query
+    query_normalized = encrypt_query(query)
+    
+    # search in encrypted index
+    if query_normalized in encrypted_index:
+        doc_ids = encrypted_index[query_normalized]['doc_ids']
+    else:
+        doc_ids = []
+    
+    # display results
+    if not doc_ids:
+        print("No documents found")
+        return
+    
+    print(f"Found {len(doc_ids)} document(s):\n")
+    for doc_id in doc_ids:
+        if doc_id in documents:
+            print(f"{'='*60}")
+            print(f"Document: {doc_id}")
+            print(f"{'='*60}")
+            print(documents[doc_id])
+            print(f"{'='*60}\n")
+
+
+def main():
+    print("\n=== Public Key Searchable Encryption (PKSE) Demo ===\n")
+    
+    # generate Paillier keys
+    generate_keys()
+    
+    docs_dir = "documents"
+    
+    # load documents
+    documents = load_documents(docs_dir)
+    
+    # build inverted index
+    inverted_index = build_inverted_index(documents)
+    
+    # encrypt index with public key
+    encrypted_index = encrypt_index(inverted_index)
+    
+    # interactive search
+    print("\nInteractive Search (type 'exit' to quit)")
+    
+    while True:
+        query = input("\nEnter search query: ").strip()
+        
+        if query.lower() == 'exit':
+            break
+        
+        if query:
+            search(query, encrypted_index, documents)
+    
+    print("\nDemo Complete\n")
+
+
+if __name__ == "__main__":
+    main()
+