# Quantum Authentication Evolution: Novel Approaches for Securing Quantum Key Distribution
## 3 QKD Protocols
### SARG04 Protocol  
The BB84 protocol uses the polarization of photons to create a shared secret key between two parties. The BB84 protocol [46] stands out as one of the most extensively employed QKD schemes renowned for its robust security mechanisms facilitated by the utilization of non-orthogonal states and random basis selections. However, its drawback lies in the protracted key exchange durations, rendering it less efficient. While BB84 exhibits moderate scalability, rendering it suitable for small-scale applications, its utility in larger networks might be limited.  
SARG04, founded by [PERSON], [PERSON], [PERSON], and [PERSON], represents a 2004 quantum cryptography protocol being evolved from the original protocol of its sort, BB84. The SARG04 protocol is specifically engineered to withstand the photon number splitting attack [33]. Subsequently, an entangled version of the SARG04 protocol showcases its superiority over BB84 in terms of long-distance communication, resilience against [PERSON]'s attack, and secret key rate [47]. The SARG04 protocol creates the n-state protocol, which maintains its reliance on two non-orthogonal quantum states [48].  
A SARG04 protocol that uses the time-bin encoding of photons to create a shared secret key between two parties. The SARG04 protocol demonstrates robust resistance against PNS attacks. Similar to the B92 protocol, SARG04 employs two non-orthogonal quantum states. However, SARG04 encodes the bit in the basis rather than the state. Notably, in contrast to BB84, [PERSON] refrains from disclosing her chosen basis to [PERSON]. During the sifting phase, [PERSON] discloses the bits he measured from the received qubits. If a bit revealed by [PERSON] differs from the corresponding bit sent by [PERSON], it indicates that they utilized different polarization bases for preparation and measurement. In such instances, [PERSON] instructs [PERSON] to accept the bit, and [PERSON] assigns the bit value associated with the unused basis during that measurement. This protocol was subsequently extended to \(n\) quantum states [49]. As a result, the SARG04 protocol boasts high security measures and enhanced efficiency compared to BB84, attributed to its utilization of only two states. Nonetheless, its scalability is relatively limited, thereby constraining its applicability within larger network infrastructures.  
Both the SARG04 and BB84 protocols entail similar phases of transmission and measurement, with congruent initial steps. However, a pivotal distinction emerges in the subsequent phase. Here, [PERSON] designates a pair of non-orthogonal states [50]. Rather than directly disclosing her chosen bases, she employs one of them to encode each bit. [PERSON] then cross-references his bases for the corresponding bits. If [PERSON] selects the appropriate base, he accurately measures the state; otherwise, he fails to retrieve the bit [33]. The SARG04 protocol has played a crucial role in establishing the security of photon pulses [51]. Moreover, in scenarios characterized by a weak signal generated by a Poissonian source and received by an imprecise detector, the SARG04 protocol proves to be particularly effective [52].