Method for transmitting at least one secret intended to be used in a transactional service for performing a transaction between a mobile terminal and an equipment, the mobile terminal running a software application intended to allow the mobile terminal to interact in the context of the transactional services, the mobile terminal incorporating or being connected to a security element securely storing at least one first signature key and/or encryption key, the method being such that, in a phase of retrieving the one or more secrets: - the software application prepares a request to retrieve the one or more secrets, which is intended to be sent to a transaction authorization system; - the software application instructs the security element to attach a signature and/or an encryption to said prepared request using at least one said first key, and transmits said signed and/or encrypted request to the transaction authorization system; - the transaction authorization system transmits said one or more secrets to the software application after verifying, by virtue of knowledge of each said first key, that said signed and/or encrypted request is authentic; and, to perform the transaction, the software application transmits said one or more secrets or information derived from said one or more secrets to the equipment, wherein the one or more secrets have a limited lifespan, the one or more secrets are stored by the software application in a memory of the mobile terminal, and wherein the transaction authorization system validates the transaction by virtue of said one or more secrets of limited lifespan, or of the information derived from said one or more secrets of limited lifespan, and wherein the security element has a second, public key contained in a certificate and a third, private key, allowing asymmetric encryption to be implemented and, in a prior initialization phase: - the software application obtains said certificate via the security element; - the software application transmits, to the transaction authorization system, a request to initialize the transactional service containing the obtained certificate, and information allowing the software application and the mobile terminal to be identified; - the transaction authorization system transmits, to the software application, each said first key in encrypted form using said second key contained in the received certificate in response to said request to initialize the transactional service; and - the software application delivers each said first key received in encrypted form to the security element in order to allow the security element to decrypt each said first key by virtue of said third key. - the software application prepares a request to retrieve the one or more secrets, which is intended to be sent to a transaction authorization system; - the software application instructs the security element to attach a signature and/or an encryption to said prepared request using at least one said first key, and transmits said signed and/or encrypted request to the transaction authorization system; - the transaction authorization system transmits said one or more secrets to the software application after verifying, by virtue of knowledge of each said first key, that said signed and/or encrypted request is authentic; - the software application obtains said certificate via the security element; - the software application transmits, to the transaction authorization system, a request to initialize the transactional service containing the obtained certificate, and information allowing the software application and the mobile terminal to be identified; - the transaction authorization system transmits, to the software application, each said first key in encrypted form using said second key contained in the received certificate in response to said request to initialize the transactional service; and - the software application delivers each said first key received in encrypted form to the security element in order to allow the security element to decrypt each said first key by virtue of said third key.