How does the server determine that the access token has not been hacked?

The server verifies the authenticity of the access token using several mechanisms:

1. Token signature: Typically, access tokens (e.g., JWT) are signed with a secret key or a private key of asymmetric encryption. The server verifies the signature using a known key to ensure the token has not been altered.

2. Expiration check: The token contains an expiration field (exp). The server checks that the token is still valid.

3. Blacklist check: If the token has been revoked, the server can check against a list of revoked tokens.

4. User and rights verification: The server verifies that the data in the token matches the expected access rights.

Example of JWT validation in Python using the PyJWT library:

import jwt

secret_key = 'your-secret'
token = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...'

try:
    payload = jwt.decode(token, secret_key, algorithms=['HS256'])
    # Token is valid
except jwt.ExpiredSignatureError:
    # Token has expired
except jwt.InvalidTokenError:
    # Token is invalid

Thus, the server trusts the token if the signature is correct and the token has not expired.