Cryptography (1–5 Levels)

MODERN CRYPTOGRAPHY:
So things get bit interesting here, after computers came into existence so came people to poke around, that is hackers and a problem to keep data safe was already a issue but bigger was how to send it safely.
We have variety of systems to implement to keep data secure but mostly you need to know about 2!
ENCRYPTION:
First, let's talk about encryption, remember the caesar's cipher? Well we took clear information and turned it into a secret that could only be read by people who knew how to solve the secret. Similarly, we have digital encryption, this is a process where we take your data and try to turn it into secret data ie(Encrypted data/Cipher Text/Message Digest) that could then be decrypted only by an authorized person to read that data.
SYMMETRIC ENCRYPTION: Remember the mailman problem?,You solved it well. Now here we apply it, send the data to your father and key separately. But now again, what if the key gets stolen by your mailman? Yup, he can open the box and steal the gift. Then one might ask that why should we use it? Pretty simple because its convenient, if you’re lazy and the data is not very confidential then you might use it, because its fast and convenient. Here the key is called a private key. So Symmetric algorithms are exactly same concept, they all have a key which has to be given in order to unlock the lock. Think of it like your Door’s lock, All your family members have access to the keys and thus it safe but one might lose the key and your entire home is compromised.
Symmetric Algorithms include DES.BLOWFISH, AES, TWOFISH, RC4, and so on.
Another thing that most people forget is the key complexity, always remember that in security, the biggest problem is convenience and that's why people have weak passwords and we still use small keys like DES 56bit. Think of it as a magic lock, the bigger the key size, the bigger the lock, and thus the more time it will take to unlock it. So you choose convenience or confidentiality:)
Key Stretching:
A thing to consider is that you can have multiple locks with multiple different key to make it more secure, similarly, in symmetric encryption we call it as key stretching where the data is encrypted multiple times often by multiple algorithms to make it more secure:)
We can also use Symmetric Algorithms securely but that will be later in the post;)