A micro controller unit devoid of a random number generator, wherein the micro controller unit comprises a communication interface with a secure element, and further comprises at least one processor configured, during an authentication of the secure element by challenge-response in the micro controller unit, to:
- receive, via the communication interface, at least one random datum generated randomly by the secure element, wherein said at least one random datum comprises a set of random data,
- generate a challenge datum specific to the micro controller unit from the received random datum,
- control sending by the communication interface of the generated challenge datum to the secure element,
- receive, via the communication interface, a response datum generated by the secure element from the challenge datum,
- determine an authentication result as a function of the received response datum,
- wherein generating the challenge datum comprises:
- selecting a first random datum and a second random datum data in the set of random data, and
- encrypting the first random datum by using the second random datum as an encryption key so as to produce an encrypted random datum, wherein the challenge datum depends on the encrypted random datum.