What is Cryptography and its usage for Cryptocurrency ?

Cryptography is the science of keeping data secure from unwanted or untrusted entities. Main goal of cryptography is to make a public open channel into a virtual secure channel such that it satisfies the following 3 properties:

1. Privacy
2. Authenticity
3. Integrity

Cryptographic mechanisms can vaguely be divided into two types: 

1. Symmetric Key Cryptography
2. Asymmetric Key Cryptography.

In Cryptocurrencies, Asymmetric Key Cryptography is used. So, we will try to understand that in this post.
Asymmetrical cryptography follows Public Key Mechanism meaning that - one key is publicly displayed and it is sharable to anyone. However the Private key should be kept secret. (Know more about private keys and how to store securely in this article)

Some attributes of Asymmetric Key Cryptography:

• Public Key Cryptography
• One key will be in public domain and the other will be Private
• Different Keys are present on both Parties (sender and receiver)
• No need of prior key agreement
• Computationally a little bit heavier.

In Blockchain, all the blocks are linked cryptographically. For every block, a hash is generated using SHA 256 Algorithm. Then, that hash is stored in that block and copied to next new block as well. In this way every block will contain two hashes : one is its own hash and other one is that of previous block.

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