Thread by @expctchaos

0/ What is Public Key Cryptography? 🧙‍♂️✨

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1/ Public key #cryptography is a cryptographic system that uses a pair of keys, a public key and a private key, to secure communication between individuals, entities, or nodes in a network.

2/ The public key is made available to anyone and is used for verification purposes, while the private key is kept secret by the owner and is used to sign messages or transactions within the system.

3/ Through the use of mathematical algorithms, the sender can encrypt a message using the recipient's public key, which can only be decrypted using the recipient's private key. This allows for secure communication without the need for the sender & recipient to share a secret key.

4/ So, in short, public key #cryptography is a way of securely communicating between individuals or nodes in a network using a pair of keys - a public key and a private key.

5/ One of the key benefits of public key cryptography is that it allows for secure communication without the need for the sender and recipient to share a secret key.

6/ This is done through the use of mathematical algorithms that enable the sender to encrypt a message using the recipient's public key, which can only be decrypted using the recipient's private key.

7/ Public key cryptography was first introduced in 1976 by Whitfield Diffie and Martin Hellman in their paper "New Directions in Cryptography."

8/ Since then, it has become a widely used method for secure communication, particularly in computer security.

9/ In 1978, Ron Rivest, Adi Shamir, and Leonard Adleman introduced the RSA algorithm, which is still widely used today as the basis for both an asymmetric cryptographic system and digital signatures.

10/ Digital signatures are an integral part of blockchain networks, which are built on the foundation of public key cryptography. I will explain those in more detail in tomorrow's threads as well.

11/ But first, let's have a look at RSA. To explain the RSA algorithm, let's use the widely adopted "Alice and Bob" framework.

12/ Starting point: Alice wants to encrypt a message and send it to Bob using an RSA-based asymmetric cryptographic system.

13/ Bob calculates all the parameters of the system by selecting two large prime numbers (p and q), calculating the product n = pq, selecting a number e that is relatively prime to (p-1)(q-1), and calculating its inverse d using the Euclidean algorithm.

14/ The private key in this system is d, while the public key is (n, e). Bob communicates the public key (n, e) to Alice, who can then use it to convert the message m into the ciphertext c: c=m^e mod n.

15/ When Bob receives the ciphertext, he can use his private key d to decrypt it: m=c^d modn. And that's a basic overview of how the RSA algorithm works!

16/ I will introduce more cryptographic primitives over the next few days, so stay tuned! 🧙‍♂️✨