Method for producing an electronic device with a disabled sensitive mode, and method for transforming such an electronic device to re-activate its sensitive mode

A method for transforming a secure electronic device, associated with a first identifier and having a sensitive mode disabled after production, for a new sensitive use, comprising the steps of:

• (i) receiving an externally computed cipher of said first identifier, said externally computed cipher having been computed with a predetermined function of said first identifier and a predetermined secret key;
• (ii) transforming an accessible metal layer of said electronic device to form an activation pattern representing said externally computed cipher of the first identifier, said accessible metal layer being transformable using a laser cutting technique that removes metallic parts in locations of said metallic layer that are defined by said computed cipher of said first identifier;
• (iii) within the secure electronic device, generating a value based upon said transformed accessible metal layer;
• (iv) computing a second identifier with said transformed electronic device by feeding a reverse function of said predetermined function with said generated value and said secret key;
• and (v) comparing said second identifier to said first identifier to trigger a comeback to said sensitive mode if said second identifier is equal to said first identifier,
• wherein said computed cipher of said first identifier is defined by N bits that are respectively associated with N continuous lines of said metallic layer belonging to a security circuit of said electronic device, and an untransformed continuous line representing a bit of said computed cipher of the first identifier that is equal to zero, while a continuous line transformed into an interrupted line represents a bit of said computed cipher of the first identifier that is equal to one.