Quantum Cryptography: Working Mechanism, Advantages, and Limitations

Context

Scientists are advocating for the adoption of Quantum Cryptography as a cutting-edge technology to safeguard sensitive communications.

Quantum Cryptography

• It is also known as Quantum encryption or Quantum Key Distribution ,refers to various cybersecurity methods for encrypting and transmitting secure data based on the naturally occurring and immutable laws of quantum mechanics.

• Working Mechanism of Quantum Cryptography:

  • Use of Photon: It uses photons (particles/waves of light) and their intrinsic properties to develop an unbreakable cryptosystem. 
    • The encryption key is determined by comparing measurements of properties from a subset of these photons. 
    • It works by the transmission of encryption keys in the form of “qubits,” also known as quantum bits, through optical fibers, analogous to bits in a binary system, ensuring high security from hacking.
  • In this process, the sender transmits photons through a polarizer with four potential polarizations and bit designations: Vertical (One bit), Horizontal (Zero bit), 45 degrees right (One bit), or 45 degrees left (Zero bit). 
  • On the receiver’s end, one of two beam splitters is utilized to discern the polarization of each incoming photon. This cycle repeats until the entire photon stream reaches the recipient. 
  • The receiver communicates to the sender the sequential use of beam splitters for photon reception. The sender cross-references this information with the sequence of polarizers employed for key transmission. 
  • Photons read using an incorrect beam splitter are disregarded, and the resulting bit sequence constitutes the encryption key.

• Advantages of Quantum Cryptography:

  • Ensuring Communication Security: 
    • It guarantees absolute security, thwarting any compromise without detection by either the sender or the recipient of the message. 
    • Information encoded within a quantum state remains impervious to replication or observation without triggering immediate notification to the concerned parties. 
  • Detects eavesdropping:  If a third party attempts to read the encoded data, then the quantum state changes, modifying the expected outcome for the users. 
  • Offers multiple methods for security: There are numerous quantum cryptography protocols used. Some, like QKD, for example, can combine with classical encryption methods to increase security.

• Limitations of Quantum Cryptography: 

  • Changes in polarization and error rates: Photons may change polarization in transit, which potentially increases error rates.
  • Range: The maximum range of quantum cryptography has typically been around 400 to 500 km, with the exception of Terra Quantum.
  • Expense: It typically requires its own infrastructure, using fiber optic lines and repeaters. 
  • Number of destinations: It is not possible to send keys to two or more locations in a quantum channel.

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