Encryption is the process of encoding information so that only authorized parties can access it. It has moved from ancient Roman substitution ciphers (Caesar Cipher) to quantum-resistant lattice algorithms. Today, it is the only thing preventing total chaos on the internet.
Symmetric Encryption (The Fast Way)
A single key is used to both Lock and Unlock the box.
Algorithm: AES (Advanced Encryption Standard).
Pros: Extremely fast. Used for encrypting hard drives (BitLocker) and large file transfers.
Cons: Key Distribution. How do I send you the key without a hacker seeing it? If we are both in the same room, easy. If we are across the world, impossible (without Asymmetric encryption).
Asymmetric Encryption (The Smart Way)
You have two keys: A Public Key (Lock) and a Private Key (Unlock).
Algorithm: RSA, ECC (Elliptic Curve).
Mechanism: I give everyone my Public Key. Anyone can use it to encrypt a message for me. But ONLY ME, with my Private Key, can decrypt it.
Pros: Solves the Key Delivery problem.
Cons: Very slow (1000x slower than AES).
1. The Hybrid Model (SSL/TLS)
Because Asymmetric is slow and Symmetric is unsafe to start, we combine them.
1. Handshake: We use Asymmetric encryption (RSA) to securely exchange a "Session Key".
2. Data Transfer: Once we both have the Session Key, we switch to Symmetric encryption (AES-256) for the rest of the conversation.
This gives us the security of RSA with the speed of AES.
2. Entropy & Key Strength
Encryption relies on randomness (Entropy).
A 256-bit key has 1.15 x 10^77 combinations.
To brute-force it, if you used every atom in the universe as a computer, it would still take trillions of years.
Weakness: Humans. If your password is "password123", the math doesn't matter.