Thank you very much. Below is their reply. Hope it's helpful for others.
ESSEC Admission Board has very exceptionnally accepted your request to have your interview through Skype.
Here is the process to follow: - The interview must take place in official premices ( your actual university, the embassy...etc ) - You must give us tomorrow the contact name, email and phone number of a person from the institution. We will then be in contact with this person who will attest your identity before the start of the interview.