app/crypto_utils.py

from nacl.secret import SecretBox
from nacl.utils import random
import base64
import json

class CryptoManager:
    
    def __init__(self, secret_key: str):
        key_bytes = secret_key.encode('utf-8')
        self.key = bytes([key_bytes[i % len(key_bytes)] for i in range(32)])
    
    def encrypt(self, data: bytes) -> dict:
        box = SecretBox(self.key)
        nonce = random(SecretBox.NONCE_SIZE)
        encrypted_msg = box.encrypt(data, nonce)
        
        ciphertext_only = encrypted_msg[SecretBox.NONCE_SIZE:]
        
        return {
            'ciphertext': base64.b64encode(ciphertext_only).decode('utf-8'),
            'nonce': base64.b64encode(nonce).decode('utf-8')
        }
    
    def decrypt(self, ciphertext: str, nonce: str) -> bytes:
        box = SecretBox(self.key)
        ciphertext_bytes = base64.b64decode(ciphertext)
        nonce_bytes = base64.b64decode(nonce)
        
        decrypted = box.decrypt(ciphertext_bytes, nonce_bytes)
        return decrypted
    
    def encrypt_json(self, data: dict) -> dict:
        json_bytes = json.dumps(data).encode('utf-8')
        return self.encrypt(json_bytes)
    
    def decrypt_json(self, ciphertext: str, nonce: str) -> dict:
        plaintext = self.decrypt(ciphertext, nonce)
        return json.loads(plaintext.decode('utf-8'))