Indeed, the transformation of the card data in Card Number Alias or token enables to connect a card number to an individual card holder or an event.
This transformation is performed by cryptography computation.
The computation will always generate the same token for the same card if the same algorithm is used. This algorithm is a one way function, so, there’s no possibility to translate from a token to a card number.
The algorithm used to generate a token may be a DES key, for instance to create a unique salt value.
Thereafter, a hash value is calculated over the salt value concatenated with the card number. The result of this operation is the card number token.