A cryptographic device configured for secure communication with a server, the device having legacy software installed thereon, the device comprising - a communication interface configured to communicate with the server, - a processor system configured with a normal mode and a secure mode, data and code in the secure mode being isolated from the normal mode, the data in the secure mode comprising at least a private key corresponding to a public key of the cryptographic device and a secret shared with the user of the device, wherein - in the normal mode, a first software is executed, the first software being configured for - receiving an encrypted message and an encrypted authentication tag from the server, the encrypted message and encrypted authentication tag being encrypted with the public key of the cryptographic device, - forwarding the encrypted message and encrypted authentication tag to second software, - in the secure mode, the second software is executed, the second software being configured for - decrypting the encrypted message and encrypted authentication tag with a private key stored in the secure mode's data, - displaying the shared secret together with the message and the decrypted authentication tag on a display of the cryptographic device to indicate to the user that the message is being displayed by software running in the secure mode, the legacy software being configured for receiving the authentication tag from the user through an input interface of the cryptographic device. - a communication interface configured to communicate with the server, - a processor system configured with a normal mode and a secure mode, data and code in the secure mode being isolated from the normal mode, the data in the secure mode comprising at least a private key corresponding to a public key of the cryptographic device and a secret shared with the user of the device, wherein - in the normal mode, a first software is executed, the first software being configured for - receiving an encrypted message and an encrypted authentication tag from the server, the encrypted message and encrypted authentication tag being encrypted with the public key of the cryptographic device, - forwarding the encrypted message and encrypted authentication tag to second software, - in the secure mode, the second software is executed, the second software being configured for - decrypting the encrypted message and encrypted authentication tag with a private key stored in the secure mode's data, - displaying the shared secret together with the message and the decrypted authentication tag on a display of the cryptographic device to indicate to the user that the message is being displayed by software running in the secure mode, the legacy software being configured for receiving the authentication tag from the user through an input interface of the cryptographic device. - in the normal mode, a first software is executed, the first software being configured for - receiving an encrypted message and an encrypted authentication tag from the server, the encrypted message and encrypted authentication tag being encrypted with the public key of the cryptographic device, - forwarding the encrypted message and encrypted authentication tag to second software, - receiving an encrypted message and an encrypted authentication tag from the server, the encrypted message and encrypted authentication tag being encrypted with the public key of the cryptographic device, - forwarding the encrypted message and encrypted authentication tag to second software, - in the secure mode, the second software is executed, the second software being configured for - decrypting the encrypted message and encrypted authentication tag with a private key stored in the secure mode's data, - displaying the shared secret together with the message and the decrypted authentication tag on a display of the cryptographic device to indicate to the user that the message is being displayed by software running in the secure mode, the legacy software being configured for receiving the authentication tag from the user through an input interface of the cryptographic device. - decrypting the encrypted message and encrypted authentication tag with a private key stored in the secure mode's data, - displaying the shared secret together with the message and the decrypted authentication tag on a display of the cryptographic device to indicate to the user that the message is being displayed by software running in the secure mode, the legacy software being configured for receiving the authentication tag from the user through an input interface of the cryptographic device.