# Trusted Third Party Application in Durable Medium e-Service
## 2 Related Works
In [14], the authors used a TTP to develop a secure sum protocol to improve the privacy and security of data (if they are collected from various sources) by performing secure multi-party computations. The authors state that the computational process that is performed by a TTP provides greater security and achieves lower computational complexity than existing secure sum protocols. Research on the application of TTP also appears in quantum computing. In [15], the authors propose a trusted third-party e-payment (TPEP) protocol based on a quantum signature without entanglement. In the protocol, to improve the security of information transmission, both the sender and the receiver of information will perform eavesdropping detection. Moreover, all participants in the whole transaction process only need to operate with a single-particle quantum \(H\) gate. According to the authors, the protocol consumes less resources and is easier to implement than other protocols with entangled states. A similar TTP application area can be found in [16]. Authors propose an innovative dynamic multiparty to multiparty quantum secret sharing scheme, where two distant groups of participants can share common secrets. In the presented solution, a TTP is required to reliably prepare all quantum resources. It means that all participants in the scheme do not need to prepare any quantum entangled resources, which effectively reduces the number of qubit generators. In the authors' opinion, the proposed protocol can be more conveniently realized in real applications and can resist various common attacks like intercept-and-resend attacks, Trojan horse attacks, collusion attacks, and entangle-and-measure attacks. In the design of smart home systems, TTP can also be applied. In such solutions, TTP plays a framework role for communication and data transmission [17]. This results in increased energy efficiency, a longer system lifetime, and faster data delivery. With the help of TTP and the event timer, the packet reception ratio (PRR) is high, at around 91%. In addition, network overhead is diminished, average packet latency is greatly reduced, and bandwidth is increased. The TTP concept is also well known and is applied to ensure security in medical applications [18]. It involves the use of a TTP to verify the authenticity of messages sent, manage cryptographic keys for end-to-end encryption, and protect against MITM or DoS cyberattacks. It is an alternative system to the well-known PKI solution. A trusted third party can also be used effectively in audio steganography. In [19], the authors use an indexing key with TTP, which increases the confidentiality of the secret message and adds another layer of protection for the decoder module. The presented methodology is used for audio files and is best suited for 32-bit files, because in their structure there are more available so-called least significant bits (LSBs), which can be used to transmit a secret message. It is worth noting that according to the definition of steganography, not only the message is encrypted, but the fact of its transmission is also kept secret. The authors in [20] present an interesting and effective approach to improving the security of data stored in the cloud for the cloud client (CC) using a half-trusted third-party auditor (TPA). The proposed concept adopts the advanced encryption standard (AES) to support the privacy of the data owner as well as a cryptographic hash function to maintain the integrity of the data owner. In addition, it uses elliptic-curve cryptography (ECC) to ensure data confidentiality, correctness, and security when data is transferred over unsecured channels. Moreover, AES encryption is also used here to secure data during the audit. This means that a half-trusted TPA cannot reveal or extract the contents of the data file. TPA is responsible for auditing cloud data integrity on behalf of CC, as TPA has knowledge and capabilities that CC does not.