Public key cryptography is a good example, which solved the seemingly impossible to solve key-distribution problem:<p><a href="https:&#x2F;&#x2F;www.coursera.org&#x2F;learn&#x2F;cryptography&#x2F;lecture&#x2F;be3ae&#x2F;the-public-key-revolution" rel="nofollow">https:&#x2F;&#x2F;www.coursera.org&#x2F;learn&#x2F;cryptography&#x2F;lecture&#x2F;be3ae&#x2F;th...</a>