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What is Czech ad ID

It is a joint project of publishers of the CPEx alliance (Czech Publisher Exchange) and Seznam.cz.

The aim is to create a uniform standard for identifying users in online enviroment that is independent of third-party cookies.

Czech ad ID system is open to publishers, agencies and advertisers.

Involved partners

How does it work?

Czech ad ID is a deterministic ID, meaning that it is bound to a unique identifier such as an e-mail or telephone number. In the Czech ad ID system, this identifier is converted into an encrypted ID that will remain stable and uniform throughout the ecosystem and for all entities involved (publishers and advertisers).

To ensure security and anonymity for end users, a double encryption system is applied, whereby the directly created “hash” is not used as an identifier, but only the output encrypted for the second time.

Therefore, advertisers and media agencies will be able to target logged-in users with very precise cross-domain and cross-device targeting. This will help publishers better monetize their space and offer targeting without losing control of their data. All this involves zero use of third-party cookies and respects user privacy (the ID is created only with the user’s consent).

The user (uzivatel@email.cz) registers and logs in to the website web-1.cz (connected in the Czech ad ID system), and provides consent during registration to the processing of personal data, including the use of Czech ad ID. The newsletter-web.cz domain “hashes” their e-mail, i.e., it turns it into a set of non-speaking characters from which the original e-mail cannot be recognized or decrypted (deciphered). The hash email username@email.cz would look, e.g., like this: 3c1b6534d81815dc1caa16587acb2b2560108b75381cfac930c63eccca567a64.

This is the first important security feature – you never send an email or phone number to the system in its original (legible) form. Only its hash is always used, from which the original data cannot be decrypted.

The publisher of the Czech ad ID website sends this hash to the service along with a query about creating the Czech ad ID itself. The service verifies that the given entity (publisher) has permission to obtain the ID and, if so, sends it back to Czech ad ID. Let’s assume that this is a completely new user who is not registered or logged-in anywhere else. In this case, there is still no record in the Czech ad ID database for the given hash, and the service will therefore generate a new ID. The new Czech ad ID is created by creating a new random set of characters for the given hash, from which the original hash cannot be decrypted back – adding yet another security element. The service saves this ID (along with the hash) and sends it back to the web publisher zpravodajsky-web.cz. Only then is such a double-encrypted ID used in the RTB ecosystem for campaign targeting and management, i.e., it is passed to the SSP by means of Prebid or RTB protocol, which sends it on to the DSP (Czech ad ID currently supports SSP Magnite and DSP Adform, with more to be added in the future).

Now suppose that the user user@email.cz registers and logs in to another website, e.g., hobby-web.cz (and also agrees to data processing). The publisher hobby-web.cz hashes the e-mail in the same way as zpravodajsky-web.cz did, and asks the Czech ad ID service to create an ID. In this case, a valid Czech ad ID already exists for the given hash, so the service returns the existing value. The user user@email.cz will thus have a uniform Czech ad ID on both websites.

In both cases, Czech ad ID is created with a predetermined, limited lifetime and after its expiration, the publisher (or another entity) must request a new one. This in turn allows users and publishers alike to maintain better control over their data.