This paper also includes a brief explanation of digital signature scheme as a related cryptographic model, whose invention was based on a Diffie-Hellman key exchange and a possible future of the protocol. I consider it important to explain what encrypting with public key is to make the way Diffie-Hellman algorithm works more understandable. This work on Diffie-Hellman key-exchange is a many-sided overview of the protocol, it's history and mathematical explanation, including a survey on it's vulnerabilities and secureness. Instead, both keys are generated secretly, as an interrelated pair.ĭiffie and Hellman published the first public-key algorithm known as a “Diffie-Hellman key exchange” the same year, finally making exchange of the keys real and secure. A public key system is so constructed that calculation of one key (the 'private key') is computationally infeasible from the other (the 'public key'), even though they are necessarily related. The situation changed in a groundbreaking year 1976 when Whitfield Diffie and Martin Hellman published a paper where they proposed the notion of public-key cryptography in which two different but mathematically related keys are used - a public key and a private key.
However, there still was no way to safely send the key – if it got to the eavesdroppers hands, data was easily decrypted. Now it was possible to create a secure cipher and send it to the recipient without one to one meeting, without using an extra-safe channel. A key specifies the transformation of plaintext into cyphertext, or vice versa during decryption. Without a key, the algorithm would have no result. The important part of encrypting and decrypting a cipher is knowing a key – a parameter that determines the functional output of a cipher. Computer use has thus supplanted linguistic cryptography, both for cipher design and cryptanalysis.īut usage of computers brought out new difficulties. Furthermore, computers were able to encrypt any type of data represented in any binary format, unlike classical ciphers which only encrypted written language texts. The development of digital computers made possible much more secure ciphers. The new cryptographic era began slightly after the World War II – the strong incentive to invent new types of ciphers and cipher machines.
But times passed and ciphers had to become more and more complex to satisfy a growing need to preserve data. The main classical cipher types were transposition ciphers, which rearranged the order of letters in a message, and substitution ciphers, which systematically replaced letters or groups of letters with other letters or groups of letters. The earliest forms of secret writing required little more than pen and paper, as most people could not read. That means, that there always was a necessity to hide important information, to make it readable only for a certain circle of people.
The earliest known use of cryptography is a carved hypertext on stone in ancient Egypt (ca 1900 BCE) and a collection of bakery recipes from Mesopotamia. This course is cross-listed and is a part of the two specializations, the Applied Cryptography specialization and the Introduction to Applied Cryptography specialization.Cryptography is a science with history that is as old as the human's knowledge of writing. This course also describes some mathematical concepts, e.g., prime factorization and discrete logarithm, which become the bases for the security of asymmetric primitives, and working knowledge of discrete mathematics will be helpful for taking this course the Symmetric Cryptography course (recommended to be taken before this course) also discusses modulo arithmetic. Lastly, we will discuss the key distribution and management for both symmetric keys and public keys and describe the important concepts in public-key distribution such as public-key authority, digital certificate, and public-key infrastructure.
Then, we will study the popular asymmetric schemes in the RSA cipher algorithm and the Diffie-Hellman Key Exchange protocol and learn how and why they work to secure communications/access. This course will first review the principles of asymmetric cryptography and describe how the use of the pair of keys can provide different security properties. In asymmetric cryptography or public-key cryptography, the sender and the receiver use a pair of public-private keys, as opposed to the same symmetric key, and therefore their cryptographic operations are asymmetric. Welcome to Asymmetric Cryptography and Key Management!