Cryptography
Cryptography is a way of sending information between people so that unauthorized people, such as eavesdroppers, cannot access or understand it. There are 2 main kinds of cryptography: symmetric and a-symmetric cryptography. In symmetric cryptography, there is only one key that is responsible for both encryption (lock) and decryption (unlock). For example, Julius Caesar, a very important figure in world history used symmetric cryptography. What Caesar did was he sent an encrypted message encrypted by moving the alphabet three letters forward. Then he sent this encrypted message to another person. The other person then decrypted the encrypted message to finally figure the message out. The decryption method was already known by the receiver. This system lasted for a very long time as there were no computers around at that time period to break the encryption.
On the other hand, in asymmetric cryptography, there are 2 types of keys, a private and a public key. A private key is a key that is known by only the authorized person and should only be known by its owner. A public key on the other hand it a key known by multiple people and can be accessed by anyone. Although a private key can be used to mathematically derive a public key, a public key cannot practically be used to recover the private key. There is a system where:
Private key => Public key => Bitcoin Address
A Bitcoin address is like an email address because it is used to send Bitcoin to someone. The difference is that a Bitcoin address is used for Bitcoin transactions instead of email.
On the contrary, an address cannot be used to recover the public key, and a public key cannot be used to recover the private key either.
This is known as a one-way function, a function that is easy to perform a mathematical compution in one direction but the reverse direction, it would become extremely difficult to perform, alomst like being impossible. But in theory, there is still a ghost of a chance that the public key could turn into a private key.
To go deeper into real world cryptography, the identities of each key are needed to be understood. There is only one sole purpose of a public key which is to encrypt, and for a private key, there are two main purposes of it. The first for decryption and the other for identification. What identification means here is just like your ID. If someone is in a private key, then the world is assuming that you are the one online. Together these 2 keys make up asymmetric cryptography which is much more secure that symmetric cryptography.
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An example of asymmetric cryptography that is used in the real world would be a question similiar to this:
“How can Alice and Bob transfer information between one another without, Eve who is intercepting their communication, being able to obtain it?
Assume Alice and Bob are super spies. Alice wants to send a message to Bob. If super spy Alice sends a direct message, an eavesdropper can steal that message and make a copy of it. If that happens the situation will get compromised. Instead, super spy Alice needs to encrypt the message using super spy Bob’s public key because when sending that encrypted message to super spy Bob, he is the only one that can decrypt it using his private key pair. Vice versa can happen as well.
Although this is a great way for secret communication between them, there is unadressed thought.
“If super spy Bob were to get the message, how does he know if the message is actually sent by super spy Alice?”
In these situations, this is where a ID comes in handy. To recap a private key is not only responsible for decrypting messages, but it holds your ID. Now instead of super spy Alice only encrypting the message using super spy Bob’s public key. Super spy Alice also creates a signature using her private key. Finally she encrypts the message along with her private key’s signature using super spy Bob’s public key. Then super spy Alice sends the message to super spy Bob. What super spy Bob does is he decrypts it using his private key and then he verifies the signature coming from super spy Alice. He verifies by extracing the signature and mathematically derives the public key out of that signature and sees whether or not the public key belongs to Alice.
MISSION ACCOMPLISHED! Both super spys were able to communicate between one another with trust, so that the eavesdropper wasn’t able to understand that message.
The key idea of cryptography is that two people can use mathematical operations to create shared or protected information while making it extremely difficult for an eavesdropper to reverse the process and discover the secret. Cryptographic systems use one-way functions, where calculating the result is easy but working backward to find the secret is computationally impractical.
Thanks for taking the time and reading through this post. More cryptography (RSA keys, and scalar elliptic curve) coming up in my next post…
