Python 3: LicenseKey - Devolens (formerly Cryptolens) Documentation

Python 3 package licensing 0.54. Reviewed source revision.

from licensing.models import LicenseKey

You normally receive this object from Key.activate, Key.get_key or LicenseKey.load_from_string. Constructing or parsing a license object yourself does not establish that its signature is valid.

Properties

Property	Meaning
`product_id`	The numeric product ID.
`id`	The numeric license ID.
`key`	The license-key string.
`created`	Creation time as a Python datetime converted using the device’s local timezone.
`expires`	Expiry time as a Python datetime converted using the device’s local timezone.
`period`	The license period in days.
`f1`	Whether feature 1 is enabled.
`f2`	Whether feature 2 is enabled.
`f3`	Whether feature 3 is enabled.
`f4`	Whether feature 4 is enabled.
`f5`	Whether feature 5 is enabled.
`f6`	Whether feature 6 is enabled.
`f7`	Whether feature 7 is enabled.
`f8`	Whether feature 8 is enabled.
`notes`	The license notes.
`block`	Whether the returned license is blocked.
`global_id`	The globally unique license identifier.
`customer`	The API’s customer data as a dictionary, or `None`.
`activated_machines`	A list of `ActivatedMachine` objects, or `None`.
`trial_activation`	Whether trial activation is configured.
`max_no_of_machines`	The machine limit; `0` disables machine registration.
`allowed_machines`	The allowed-machine value (whitelist) as received from the API.
`data_objects`	A list of API dictionaries, or `None`. Property names such as `Name` and `StringValue` retain their API casing.
`sign_date`	The signed timestamp as a Python datetime converted using the device’s local timezone.
`reseller`	A `Reseller` object, or `None`.
`raw_response`	The original `Response` envelope used when saving the signed response.

from_response

Decode a response envelope into a license object.

LicenseKey.from_response(response)

Parameters

Parameter	Default	Meaning
`response`	Required	A `Response` object containing the signed-response envelope.

Result

Returns a LicenseKey object, including converted dates and activation objects. Raises for rejected, malformed or incomplete data, including timestamps outside the platform’s supported range.

Checks

Decodes and parses the data; it does not verify the signature. Use Key.activate, Key.get_key or load_from_string when you need the SDK to verify it.

save_as_string

Serialize the license’s original signed response.

license_key.save_as_string()

Result

Returns a JSON string that can be saved and later passed to load_from_string. Requires a usable raw_response; an object constructed without it can raise an exception.

Checks

Preserves the original signed response and signed timestamp. It does not create a new signature or restart the offline allowance.

Example

After successful activation, license_key is the first item of the result. This example saves its original signed response.

with open("licensefile.skm", "w") as license_file:
    license_file.write(license_key.save_as_string())

load_from_string

Load and verify a previously saved signed response.

LicenseKey.load_from_string(rsa_pub_key, string, signature_expiration_interval=-1)

Parameters

Parameter	Default	Meaning
`rsa_pub_key`	Required	Your account’s complete RSA public key in XML form.
`string`	Required	The serialized string previously returned by `save_as_string()`.
`signature_expiration_interval`	`-1`	The maximum age in days. Positive values enable the age check; `0` and negative values disable it.

Result

Returns a LicenseKey object, or None when it cannot load and verify the data. Returns None for malformed data, an invalid RSA key, a failed signature, a parsing failure, or a response older than a positive age limit.

Checks

Verifies the license signature. A positive signature_expiration_interval also checks age from the signed timestamp using the device clock; the default -1 disables that age check. It does not enforce license expiry, machine binding, product or feature requirements.

Example

Replace the RSA public key placeholder with your account’s key. Here, 3 is the maximum signed-response age in days.

with open("licensefile.skm", "r") as license_file:
    license_key = LicenseKey.load_from_string(
        "YOUR_RSA_PUBLIC_KEY", license_file.read(), 3)
if license_key is None:
    print("Could not load a verified response within the age limit.")

FAQ

Does Saving the File Restart Its Offline Allowance?

No. The age check uses the signed timestamp in the response. Copying or saving the file does not change that timestamp.

Does the Age Check Prevent Clock Rollback?

No. The signature protects the timestamp from being edited, but the SDK compares it with the device clock. Changing that clock can affect the age check. See offline verification for the limitation and the other checks your application needs.

Python SDK Reference

​Properties

​from_response

​Parameters

​Result

​Checks

​save_as_string

​Result

​Checks

​Example

​load_from_string

​Parameters

​Result

​Checks

​Example

​FAQ

Properties

from_response

Parameters

Result

Checks

save_as_string

Result

Checks

Example

load_from_string

Parameters

Result

Checks

Example

FAQ