Quantum
Cryptography
What is Cryptography?
• Protecting Information by using mathematical techniques
• Plain text is encrypted  creates cypher text
• Cipher text is decrypted  back to plain text
Example of cryptography (Activity)
• Caesar cipher – plain text is encrypted by shifting the letters by a specific number
• Example: Hello World (key: 3)  Khoor Zruog
• Try encrypting “Caesar” with key 7
What is Quantum Cryptography?
• Uses Quantum Mechanics to securely transfer encryption keys
• Attempts to make unbreakable communication by detecting any attempt to intercept or tamper with the key
• Most common method: Quantum Key Distribution (QKD)
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Uses quantum particles such as photons to share a secret key between two particles securely
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Photons (light particles) are sent over fiber optic cables
•
Each photon has a random quantum state
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Collectively, photons sent make up a stream of 1s and 0s (this stream of binary are called qubits)
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When the photon reaches the receiver, it passes through a beam splitter forcing the photon to go through one path or another
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The photon goes into a photon collector, and the receiver responds to the sender with the sequence of photons sent and the
sender compares it with the emitter that sent each proton
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Photons in the wrong collector are discarded; the remaining makes up the encryption key for the data being transmitted.
Pros
• Unbreakable key transmission
• Measuring a quantum state disturbs it making it difficult to check the key without being detected
• Perfect forward secrecy
• Keys are used once and then discarded which reduces the consequences if the key is leaked in the
future
• Stronger than classical encryption
• Not based on mathematical problems which can be cracked with advances in computing
Cons
• Expensive and complex
• Requires advanced technologies including specialized hardware
• Short distance limits
• Works best over short distances limited by current fibre optic and signal loss issues
• Slow transmission speed
• Typically, slower than traditional methods
• Still evolving
• Still not widely available and new
• Only secures key exchange
• Quantum cryptography only protects the key and not the actual data as traditional encryption algorithms
required for that
Thank you