Public Key Cryptography

Suppose that you are connecting to your bank’s website. It is possible that someone could intercept any communication between you and your bank, so you’ll want to encrypt the communication. The problem is that all the encryption methods we’ve discussed require that both parties have already agreed on a shared secret encryption key. How can you and your bank agree on a key if you haven’t already?

This becomes the goal of public key cryptography – to provide a way for two parties to agree on a key without a snooping third party being able to determine the key. The method relies on a one-way function; something that is easy to do one way, but hard to reverse. We will explore the Diffie-Hellman-Merkle key exchange method.

Public key cryptography involves the use of key pairs, which consist of a public key and a private key. The public key is available to everyone and is used to encrypt data, while the private key is kept secret and is used to decrypt the data. The keys are mathematically related, so if one key is used to encrypt data, only the corresponding key can decrypt it. This ensures secure communication between parties.

The encryption process in public key cryptography involves using the recipient’s public key to encrypt the data, which can then be safely transmitted over a public network. Only the recipient’s private key can decrypt the data, ensuring that it remains confidential. Similarly, when the recipient needs to send a message back to the sender, they can use the sender’s public key to encrypt the data, which can only be decrypted using the sender’s private key.

Public key cryptography also allows for the creation of digital signatures, which provide a way to verify the authenticity of data or messages. A digital signature is created by applying a mathematical algorithm to the data using the sender’s private key. The resulting signature can be sent along with the data and can be verified by anyone who has access to the sender’s public key. If the data has been tampered with or altered in any way, the digital signature will not match, indicating that the data is not authentic.