# Key Based Cryptographic Algorithms

Hello Everyone.

In my previous blogs, we have come to know a little about Technique based cryptographic algorithms and their working mechanism. In this blog, I will be discussing about Key based cryptographic algorithms. Key based algorithms are somewhat harder than technique based algorithms. These involve more complex concepts that make these algorithms far more secure than technique based algorithms.

Before going into details of Key based algorithms, there is another small classification of the algorithms that categorizes it into two parts.

1. Stream Cipher - In this cipher, characters are processed one at a time.

2. Block Cipher - In this cipher, a fixed size block is extracted from the whole plain text and then,  the character is processed one at a time. We will start to see the significance of this classification once we start digging into the algorithm demonstrations.

So, let's come back to the classification of Key based algorithms. There are two types.

1. Symmetric Key Cryptography or Private Key Cryptography

In this type of cryptography, only one key is used to encrypt and decrypt the message. Both parties must agree upon the same key before any transmission begins. This key should be only known to the two parties and no one else. That's why it is also called Private Key Cryptography or Secret Key Cryptography.

Example - DES, IDEA, RC4, RC5, BlowFish, AES, etc.

2. Asymmetric Key Cryptography or Public Key Cryptography

In this type of cryptography, two different keys are used - one is a public key that is available to all for encrypting the message; the other one is a private key which is available only to the receiver, for decrypting the message. Both the keys are generated by receiver but only the public key is sent to the sender for encryption. Any sender can encrypt the message with the public key but only the receiver can decrypt the message with the private key. This feature ensures that only the intended person gets to read the message and no one else. That's why it is also called Public Key Cryptography.

Example - Merkle's Puzzles, RSA, ElGamal, ECC, etc.

In my next blogs, I will start with the demonstrations of Symmetric Key Cryptographic Algorithms. That's all for this blog. I hope you find it useful. Till then, keep coding.

http://cryptobysourav.blogspot.in/2016/08/key-based-cryptographic-algorithms.html

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