Quantum computing harnesses quantum phenomena to perform calculations using qubits, enabling parallel processing and faster problem-solving. This technology poses significant challenges to traditional cryptography, threatening the security of widely-used algorithms like RSA and ECC.

To address these challenges, post-quantum cryptography is being developed. These new algorithms are designed to resist quantum attacks, ensuring data confidentiality and integrity in a future where quantum computers are commonplace. Quantum key distribution offers another layer of security by leveraging quantum mechanics for secure key exchange.

Quantum Computing and Cryptography

Principles of quantum computing

• Quantum computing harnesses quantum-mechanical phenomena such as superposition and entanglement to perform calculations
• Utilizes qubits (quantum bits) which can exist in multiple states simultaneously, unlike classical bits limited to either 0 or 1
• Enables parallel processing and solving complex problems significantly faster than classical computers (Shor's algorithm, Grover's algorithm)
• Potential impact on cybersecurity threatens the security of traditional cryptographic algorithms like RSA and ECC

Quantum challenges to cryptography

• Quantum computers can solve certain mathematical problems much faster than classical computers
  • Shor's algorithm efficiently factorizes large numbers, breaking the security of RSA which relies on the difficulty of this problem
  • Grover's algorithm speeds up brute-force attacks on symmetric-key cryptography (AES, DES)
• Larger key sizes are required to maintain the same level of security against quantum attacks
• Necessitates the development and adoption of quantum-resistant cryptographic algorithms

Post-quantum cryptography fundamentals

• Post-quantum cryptography (PQC) designs algorithms to be secure against quantum computers
• Based on mathematical problems believed to be hard even for quantum computers to solve efficiently
• Examples include lattice-based (NTRU), code-based (McEliece), multivariate (Rainbow), hash-based (SPHINCS+), and supersingular isogeny cryptography (SIDH)
• Ensures the confidentiality and integrity of data in the presence of quantum computers
• Provides long-term security for sensitive information and enables secure communication and authentication in a post-quantum world

Quantum key distribution applications

• Quantum key distribution (QKD) uses quantum mechanics principles to securely exchange cryptographic keys
  • Detects eavesdropping attempts based on the no-cloning theorem and the Heisenberg uncertainty principle
  • Ensures unconditional security of the shared key, as any measurement of the quantum state alters it detectably
• Establishes secure communication channels for sensitive data transmission (government communications, financial transactions)
• Enables secure key exchange for symmetric-key cryptography, enhancing the security of existing encryption schemes
• Finds use in high-security environments such as government, military, and financial institutions
• Limitations and challenges include requiring specialized hardware, limited communication range, and integration with existing network infrastructure