## 4 Discussion  
We discuss benefits and disadvantages of our concept in this section.  
Benefits of our Identification and Authentication SchemeOur concept has the advantages that it is user-centric, that it can make use of information from different sources, and that it helps in establishing trust relationships with other home networks. It is also very extensible: information about authenticity and trustworthiness could be derived from other sources, like, e.g., social networks where fingerprints of home networks can be stored in a profile.  
Users' social relations are reflected by the exchange of certificates in a convenient way. At the same time, it is possible for users to contact previously unknown domains (homes) and access rights can be determined in a semi-automated way. The scheme is also useful for the common case where domains have no exchanged keys or even no previous contact. It scales with the available information and aids users in making informed choices while not annoying them with unnecessarily technical background.  
Benefits of TPM Usage in Home NetworksUsing the TPM as a hardware safeguard has the advantage that stealing the Home Key becomes much less feasible. The attacker would need to break the security mechanisms provided by the TPM. To our knowledge, no software-based attack that succeeds in the theft of a key from a TPM is known. However, once such systems are employed and there is enough financial incentive for identity theft of home networks, we expect that such attacks will appear. Our solution cannot prevent this, and software patches that fix exploits will continue to be needed. Migratable or non-migratable keys can be used as the Home Key. The first option makes it possible to  
Figure 6: Remote Attestation of the Home CA. When a certificate needs to be created (1), the Home CA requests the home owner to enter the PIN (2). The owner triggers the RA process (3–5) and enters the PIN (7) if the Verifier assesses the Home CA as trustworthy (6). The Home CA now is able to unlock the HK and create and deliver the certificate (8 + 9).  
backup the Home Key which prevents the loss of the HK in case the TPM is defective. The drawback is that a migratable Home Key is less trustworthy than a non-migratable one.  
Malware on the TPM-enabled Home CA could still interfere during the certification process. Remote Attestation can be applied to fight such attacks. The Remote Attestation mechanism is only feasible for small scale operating systems. The first option would be to use a dedicated device as a Home CA. Dropping hardware prices make this possible. The second option would be to use virtualized TPM-enabled machines. Here, trusted services can run in different virtual machines with a high level of isolation. This will provide a high level of flexibility. But here the system security depends heavily on the security of the hypervisor used. If malware running in a virtual machine succeeded in compromising the hypervisor, it might be able to tamper with the communication between the virtualized TPM and the hardware TPM. This could lead to wrong measurement values and a remote attestation without effect.  
Although there are some unsolved problems when using TPM technology, and TPM is certainly not the silver bullet that it is sometimes touted to be, we believe that on the whole it can be used effectively to enhance security.