A method for the duplication of original electronic keys used in the road vehicle transport sector provided with coded and encrypted electronic authentication. The method including the steps of intercepting a radio-electric interrogating signal of an encrypted electronic authentication system transmitted between a central processing unit of a vehicle and an original key, decrypting a secret code from a random code at a key duplicating device, performing an interrogation process by transmitting a radio-electric signal including said decrypted secret code from said duplicator, to said original key, receiving a password, transmitted by said original key, at said duplicator in response to the transmission of the secret code, and transferring the password to a blank key.