An explanation of quantum cryptography

<p><i>In this video, Informa TechTarget product marketing associate Katie Donegan explains what quantum cryptography is, how it differs from classical cryptography and how it works.</i></p>
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<p>Math might not offer the security you need … but physics might.</p>
<p>Classical cryptography that encrypts messages with mathematical equations is secure enough for classical computing — but with the emergence of quantum computing, it might not be enough protection. That’s <a href=”https://www.techtarget.com/searchsecurity/definition/quantum-cryptography”>where quantum cryptography comes in</a>: It uses physics instead of math.</p>
<p>Here, we’ll talk about why quantum cryptography is so secure. However, despite the advantages, there are still limits and challenges to quantum cryptography and quantum key distribution (QKD).</p>
<p>Quantum cryptography uses particles of light, or photons, to transmit cryptographic <a href=”https://www.techtarget.com/searchsecurity/definition/key”>keys</a> over fiber optic wire. The photons represent <a href=”https://www.techtarget.com/whatis/definition/bit-binary-digit”>binary bits</a>, meaning 0s and 1s. It’s a completely secure system because of these properties of quantum mechanics:</p>
<ul class=”default-list”>
<li>Particles can exist in more than one place or state at a time.</li>
<li>A quantum property cannot be observed without changing or disturbing it.</li>
<li>Whole particles cannot be copied.</li>
</ul>
<p>Quantum cryptography follows a model developed in 1984 that goes like this:</p>
<p>Alice wishes to send Bob a message. Alice initiates the message, sending Bob a key or stream of photons. But the photons first pass through a polarizer, polarizing each photon in a certain state — horizontal, vertical, diagonal to the right or diagonal to the left.</p>
<p>As Bob receives the photons, he doesn’t know the correct polarization of the photons, so he randomly uses one of two beam splitters to read each photon’s polarization and decipher the key. Alice

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