Cryptographic activation system comprising an activation centre (6, 8) and an assembly of first equipment item(s), said activation centre and said equipment items being connected by a telecommunications network, in which each first equipment item is adapted to encrypt, respectively decrypt, data as a function of a main encryption key, when said first equipment item has said decrypted main encryption key, said activation system being characterised in that: each first equipment item comprises a non-volatile memory storing a main encryption key encrypted by a first secondary encryption key and is adapted, upon start-up of the first equipment item, to generate a cryptographic activation request indicating an identifier of said first equipment item and to transmit said cryptographic activation request to the activation centre via the telecommunications network; the activation centre is adapted to receive said activation request, in order to validate the activation request as a function of at least the identifier of the first equipment item indicated in the request, and in order, only if it has validated the activation request, to generate an activation response message comprising said first secondary data key of the first equipment item and in order to transmit said activation response to the first equipment item via the telecommunications network; said first equipment item being adapted to receive the cryptographic activation response, in order to finalise its cryptographic activation by extracting the first secondary data key of the first equipment item from said response, by decrypting said main encryption key stored in the memory with the extracted first secondary encryption key and thus obtaining said unencrypted main encryption key with a view to encryption of data by said first equipment item with said main key; said first equipment item is, furthermore, adapted to obtain a second secondary encryption key, in order to encrypt the main encryption key with said obtained second secondary encryption key, in order to store said encrypted main encryption key in the non-volatile memory; and said first equipment item being, furthermore, adapted, prior to being put out of service subsequent to said restart, to delete, from its non-volatile memory, the unencrypted main encryption key and the unencrypted second secondary encryption key. each first equipment item comprises a non-volatile memory storing a main encryption key encrypted by a first secondary encryption key and is adapted, upon start-up of the first equipment item, to generate a cryptographic activation request indicating an identifier of said first equipment item and to transmit said cryptographic activation request to the activation centre via the telecommunications network; the activation centre is adapted to receive said activation request, in order to validate the activation request as a function of at least the identifier of the first equipment item indicated in the request, and in order, only if it has validated the activation request, to generate an activation response message comprising said first secondary data key of the first equipment item and in order to transmit said activation response to the first equipment item via the telecommunications network; said first equipment item being adapted to receive the cryptographic activation response, in order to finalise its cryptographic activation by extracting the first secondary data key of the first equipment item from said response, by decrypting said main encryption key stored in the memory with the extracted first secondary encryption key and thus obtaining said unencrypted main encryption key with a view to encryption of data by said first equipment item with said main key; said first equipment item is, furthermore, adapted to obtain a second secondary encryption key, in order to encrypt the main encryption key with said obtained second secondary encryption key, in order to store said encrypted main encryption key in the non-volatile memory; and said first equipment item being, furthermore, adapted, prior to being put out of service subsequent to said restart, to delete, from its non-volatile memory, the unencrypted main encryption key and the unencrypted second secondary encryption key.