Cryptography (1–5 Levels)

Asymmetric Encryption:
Now we had issues with symmetric encryption, the issue was there was a single key that would lock and unlock the lock thus if that key fell into wrong hands then your information is compromised. Asymmetric Encryption solves that very issue. Here instead of one key, we use two keys but its different from key stretching by that the keys are derived but not directly related to each other. Let me explain:
In Asymmetric Encryption we have 2 Keys, 1 is private and the other is public. The trick is that the public key is derived or made out of part of the private key but if you have the public key, you cannot make a private key as you don’t know the rest of the information. This is vague to keep it simple. So you want to send a mail to your father again but this time the mailman might steal the key. No worries, Asymmetric encryption is at the rescue. Both you and your father generate 2 keys, 2 for him and 2 for you 2+2=4. Now as the name suggest the public key is for the public, so you ask your father for his public key and you take the mail and use the public key of your father to lock it. The mailman also asks your father for his public key and he gets it. You might ask, will he be able to open the box? NOPE!, the beauty here is that the public key can only lock the information, so it can only lock the box but not unlock it, so who can? Remember that both keys belong to your father, since you used his public key to encrypt the information, he can use it to decrypt it or open the lock since the public key is derived from the private key. Now if your father wants to mail the gift back since he does not like it, he will use your public key to lock it(encrypt) and you can use your private key to unlock(decrypt) it. The mailman is sad since he thought he could use the public key to unlock it:(
REMEMBER THE RULE:
PUBLIC KEY = ENCRYPT
PRIVATE KEY = DECRYPT

CHEAP DIAGRAM WHICH DOES NOT EXPLAIN ANYTHING
So now that you have your concept clear, lets talk about which algorithms uses asymmetric encryption:
Rivest, Shamir, and Adelman (RSA): RSA is named after the three people who invented the algorithm. The keys were the first private and public key pairs, and they start at 1,024, 2,046, 3,072, and 4,096 bits. They are used for encryption and digital signatures.
Digital Signature Algorithm (DSA): DSA keys are used for digital signatures; they start at 512 bits, but their 1,024-bit and 2,046-bit keys are faster than RSA for digital signatures.
Elliptic Curve Cryptography (ECC): ECC is a small, fast key that is used for encryption in small mobile devices. However, AES-256 is used in military mobile cell phones. It uses less processing than other encryptions. Ephemeral Keys: Ephemeral keys are short-lived keys. They are used for a single session, and there are two of them:
a. Diffie Hellman Ephemeral (DHE)
b. Elliptic Curve Diffie Hellman Ephemeral (ECDHE)
Pretty Good Privacy (PGP): PGP is used between two users to set up an asymmetric encryption and digital signatures. For PGP to operate, you need a private and public key pair. The first stage in using PGP is to exchange the keys. It uses RSA keys.
GnuPG: GnuPG is a free version of OpenPGP; it is also known as PGP. It uses RSA keys.