A method of combining symmetric and asymmetric cryptography for recording and playing back a media data stream, performed by an unmanned aircraft system, UAS, comprising an unmanned aerial vehicle, UAV, and a UAV ground station, the method comprising: generating, by the UAV ground station, a public key and a corresponding private key (PRIV); password protecting, by the UAV ground station, the private key (PRIV) by means of a password provided to the UAV ground station, wherein the password protecting comprises: generating an advanced encryption standard encryption standard, AES, key based, at least in part, on the password provided; encrypting the private key using the AES key and an AES algorithm in Galois/Counter Mode, AES-GCM; storing the encrypted private key within the UAV ground station; and erasing the private key from the UAV ground station; after a first mission is started: generating, by the UAV, a symmetric data encryption key, encrypting, by the UAV, said media data stream by means of the symmetric data encryption key, wherein the media data stream is generated by a media data capturing device of the UAV, encrypting, by the UAV, the symmetric data encryption key by means of the public key; and transmitting the encrypted symmetric data encryption key and the encrypted media data stream to the UAV ground station for storage; storing, by the UAV ground station, the encrypted symmetric data encryption key and the encrypted media data stream to the UAV ground station from the UAV; wherein the generating the symmetric data encryption key, the encrypting said media data stream, the encrypting the symmetric data encryption key, and the storing are performed without entry of the password. generating, by the UAV ground station, a public key and a corresponding private key (PRIV); password protecting, by the UAV ground station, the private key (PRIV) by means of a password provided to the UAV ground station, wherein the password protecting comprises: generating an advanced encryption standard encryption standard, AES, key based, at least in part, on the password provided; encrypting the private key using the AES key and an AES algorithm in Galois/Counter Mode, AES-GCM; storing the encrypted private key within the UAV ground station; and erasing the private key from the UAV ground station; generating an advanced encryption standard encryption standard, AES, key based, at least in part, on the password provided; encrypting the private key using the AES key and an AES algorithm in Galois/Counter Mode, AES-GCM; storing the encrypted private key within the UAV ground station; and erasing the private key from the UAV ground station; after a first mission is started: generating, by the UAV, a symmetric data encryption key, encrypting, by the UAV, said media data stream by means of the symmetric data encryption key, wherein the media data stream is generated by a media data capturing device of the UAV, encrypting, by the UAV, the symmetric data encryption key by means of the public key; and transmitting the encrypted symmetric data encryption key and the encrypted media data stream to the UAV ground station for storage; storing, by the UAV ground station, the encrypted symmetric data encryption key and the encrypted media data stream to the UAV ground station from the UAV; generating, by the UAV, a symmetric data encryption key, encrypting, by the UAV, said media data stream by means of the symmetric data encryption key, wherein the media data stream is generated by a media data capturing device of the UAV, encrypting, by the UAV, the symmetric data encryption key by means of the public key; and transmitting the encrypted symmetric data encryption key and the encrypted media data stream to the UAV ground station for storage; storing, by the UAV ground station, the encrypted symmetric data encryption key and the encrypted media data stream to the UAV ground station from the UAV; wherein the generating the symmetric data encryption key, the encrypting said media data stream, the encrypting the symmetric data encryption key, and the storing are performed without entry of the password.