The invention concerns secure data transfer from a first radio communication device of a first party to a second radio communication device. A random first symmetric key is generated at the first terminal device. User data of the first terminal device is encrypted with the first symmetric key. The first symmetric key is encrypted with a public key of a third party. The encrypted first symmetric key is sent from the first terminal device to the second terminal device via a transfer device. The encrypted first symmetric key is decrypted at the second terminal device by utilizing a secret key associated with the public key and comprised in a security device of the third party. The encrypted user data is sent from the first terminal device to the second terminal device via the transfer device. The encrypted user data is decrypted at the second terminal device with the first symmetric key.