00:00 Cryptography is the process of communicating in or deciphering secret writings or ciphers, and its origins can be traced back to ancient times when there was a need to hide messages.

02:11 The substitution cipher was an early form of cryptography where letters were shifted by a set number, and frequency analysis of characters played a key role in deciphering messages.

04:13 The development of more complex encryption systems, including the one-time pad, allowed for more secure communication, but the distribution of keys remained a challenge.

06:09 World War II saw the introduction of electromechanical encryption machines, including the German enigma machine, which had three rotors of letters and electronic circuits, and the British and Americans also used their own encryption machines, but it wasn't until after the war that cryptography became a science with the rise of digital computers and the work of Claude Shannon.

08:02 Public key encryption, proposed in 1976, eliminates the need to share a copy of the key with all parties involved in an encrypted communication, allowing each party to have a public key known to the world and a private key known only to themselves.

09:58 An increase in key size by just one bit doubles the time it takes to decrypt, with estimates suggesting it would take about 14 billion years to crack a code encrypted with a 2,048-bit key, and the energy required to crack a 4,096-bit key is estimated to be enough to boil away all of the oceans and turn the earth into a wasteland; hash functions are a one-way function used in digital cryptography to map any number onto a number of a set size, and are a foundation for blockchain transactions and cryptocurrencies like Bitcoin; steganography is the science of hiding messages by embedding them inside other files.

12:10 Cryptography has evolved from a simple method to discourage prying eyes to the foundation of modern economy, playing a crucial role in electronic commerce and digital communication.