A method for securing update processing for mobile payment application installed in a mobile device from an update issuer through a gateway, said update processing transiting in an unsecure network between the mobile device and the gateway, wherein when an over-the-air issuer update of said mobile payment application is initiated, the mobile payment application performs an administrative payment transaction according to the following steps: - incrementing a transaction counter, deriving a session encryption key ENC from the transaction counter value and a gateway encryption key KENC loaded into the mobile payment application, - encrypting user sensitive data with the session encryption key ENC, user sensitive data comprising the contents of a magnetic-stripe data track(s), fully or partially (track 1, track 2, track 3),and/or a Primary Account Number PAN, - generating a cryptogram, elaborating an update request message comprising the encrypted sensitive data, the cryptogram, the transaction counter value, and an application identifier of the mobile payment application, - sending the update request message from the mobile payment application through the mobile device to the gateway, - the gateway being configured to perform the following steps upon reception of the update request message: - computing a gateway encryption key KENC from the application identifier extracted from the received updates request message and a gateway master key personalized into the gateway, deriving the session encryption key ENC from the current transaction counter value from the received updates request message and the computed gateway encryption key KENC, - decrypting the sensitive data of the update request message from the derived session encryption key ENC, sending the update request message comprising the decrypted sensitive data to the update issuer of the mobile payment application for processing through secured processing network, - forwarding the update response message from the issuer to the mobile payment application, the update response message comprising information for configuring the mobile payment application as well as information for issuer updates to the mobile payment application. - incrementing a transaction counter, deriving a session encryption key ENC from the transaction counter value and a gateway encryption key KENC loaded into the mobile payment application, - encrypting user sensitive data with the session encryption key ENC, user sensitive data comprising the contents of a magnetic-stripe data track(s), fully or partially (track 1, track 2, track 3),and/or a Primary Account Number PAN, - generating a cryptogram, elaborating an update request message comprising the encrypted sensitive data, the cryptogram, the transaction counter value, and an application identifier of the mobile payment application, - sending the update request message from the mobile payment application through the mobile device to the gateway, - the gateway being configured to perform the following steps upon reception of the update request message: - computing a gateway encryption key KENC from the application identifier extracted from the received updates request message and a gateway master key personalized into the gateway, deriving the session encryption key ENC from the current transaction counter value from the received updates request message and the computed gateway encryption key KENC, - decrypting the sensitive data of the update request message from the derived session encryption key ENC, sending the update request message comprising the decrypted sensitive data to the update issuer of the mobile payment application for processing through secured processing network, - forwarding the update response message from the issuer to the mobile payment application, the update response message comprising information for configuring the mobile payment application as well as information for issuer updates to the mobile payment application. <EOS>