Private/Public Key Cryptography

Lets dive into private/public key cryptography today. This is
a simple concept that can seem a lot more complex than it
really is.

1. Symmetric cryptography

This is the most simple form of cryptography to grasp. In this
case we have one private key and it is shared by the server
and the client. Lets say we have a bank and a customer. The
bank and the customer obviously want their communication to be secured from hackers/criminals etc.
They devise a scheme where the bank will encrypt any
messages it sends to the customer using a private key. It will
send then send the message and the private key to the
customer. The customer will then decrypt the message
using the private key sent from the bank. When the
customer wants to respond to the bank then they will
encrypt their message using that same private key and send
the encrypted message back to the bank. The bank will then
decrypt the message using the private key. This is a great
scheme but the problem is that if anyone ever gets their
hands on that private key they will be able to decrypt
messages sent from the bank and the customer. This single
point of failure just won’t do.

2. Asymmetric cryptography

This is the much more commonly used form of
cryptography. Our bank now creates a private key and
distributes public keys to all customers that want to
communicate with it. The private key is the only key that
can decrypt information that has been encrypted by the
public key. So when the customer sends sensitive
information to the bank, they can encrypt their message
using the bank’s public key and rest safely knowing that the
bank will be the only one that as the ability to decrypt the
message.

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