Blockchain is essentially a decentralized algorithm for distributed storage and processing , using a non immutable data structures and securing them with signatures and keys . These sequential chain of records called blocks , can contains almost anything from timestamped transactions , metadata , contracts , files etc just as long as they are chained using hash pointers to previous blocks .
what is a hash ?
function f (x) = y , takes an i/o and give a determined o/p . example heaxadecimeal output of my name , md5(altanai bisht) = 2b9e76d57842ebafaf19fd33bb3573a3.
These are irreversible ie one cant find the i/p from o/p . For this u need to try every combination using brute force. Hence these are generally used for cross verification without revealing the information itself .
Who are miners ?
Application of block chain :
Market analysts and industry specialist have said that block-chain is a revolutionizing technology which will create a decentralized network for not just currency exchange but also many other aspects such as double spent problem , universal identities , document management etc . Example : Bitcoin protocol , which contains a full record of every transaction ever executed with the currency at any time in past. It is also a solution to problem like black – money , double spending , tax evasions etc. Other areas include:
- Decentralizing document keeping such as government records , digital assets , equity information , medical and health records etc . The system also provide data ownership and Intellectual property protection .
- Fintech as AML( Anti money laundering) , eKYC ( Know Your customer ) , epay , loans, stock trading .
- Smart contracts such as in ethereum . Allows to keep program code that would execute on an event.
- Shared economy for a p2p payment system .
- Crowdfunding , works on paradigm of token owner’s voting and cooperation in decisions for crowd-sourced venture capital funds .
- Micro payments / fractional concurrency for small amounts suits power selling and buying such as on solar renewable power micro grid
Since a block chain is a ledger of facts shared across many peer nodes , all communication and inter node transaction uses the power of crypto to authenticate each other and validate each others requests from the genesis block .
what is a genesis block ?
First block of blockchain which needs to be hard-coded into software . It is the only block which does not reference a previous block .
As any peer wants to add a fact to the ledger , a consensus needs to be obtained from the network. This way of network agreement ensures that fraudulent behavior is prevented .
Example : bitcoin’s genesis block
01000000 - version 0000000000000000000000000000000000000000000000000000000000000000 - prev block 3BA3EDFD7A7B12B27AC72C3E67768F617FC81BC3888A51323A9FB8AA4B1E5E4A - merkle root 29AB5F49 - timestamp FFFF001D - bits 1DAC2B7C - nonce 01 - number of transactions 01000000 - version 01 - input 0000000000000000000000000000000000000000000000000000000000000000FFFFFFFF - prev output 4D - script length 04FFFF001D0104455468652054696D65732030332F4A616E2F32303039204368616E63656C6C6F72206F6E206272696E6B206F66207365636F6E64206261696C6F757420666F722062616E6B73 - scriptsig FFFFFFFF - sequence 01 - outputs 00F2052A01000000 - 50 BTC 43 - pk_script length 4104678AFDB0FE5548271967F1A67130B7105CD6A828E03909A67962E0EA1F61DEB649F6BC3F4CEF38C4F35504E51EC112DE5C384DF7BA0B8D578A4C702B6BF11D5FAC - pk_script 00000000 - lock time
There is only one path from top block on chain to genesis root , however there can many forks upwards from genesis block . It is so because blocks may be created within a short span of time or be under processing . One of the two block will be added to main chain and other will be orphaned or added to pool of queued transactions or even be lost.
Steps to Programming a simple block-chain application :
Lets assume we are creating a block chain for call records.
Create a class for member function and variables
define variable chain as an array and transactions as array as well
create functions for createNewBlock() , createNewTranscation() , fetchLastBlock() ,
boolean isBlockValid ( newBlock , oldBlock) – checks if the oldblocks index is sequentially aligned with new block and whether old blocks hash is equal to new blocks previous hash . Also calculates whether hash of new block is actually same as the supplied hash value in new block ( give below) .
hashBlock( block ) – to create the hashes we need to add in block. Basically a SHA 256 hash of concatenated arguments as index, timestamp, message , previous hash and a nonce . example pseudo code :
All block-chains a\re deterministic state machines and transactions act upon them . Consensus filters out the invalid ones and reaches on agreement with valid ones.
DPOS (Delegated Proof of Stake)
A consensus algorithm used for electing producers and scheduling them in a fair and democratic way . It works on the simple principle that longest chain wins therefore incases of multiple forks or network disruption also , if an honest peer finds out a valid strictly longer chain , it will switch from its current fork to the longer chain. We assume that in all conditions , no other chain forked can be longer if 2/3 of producers are honest as 2/3 + 1 confirmations are required .
In crypto we trust !
Block chain is primarily 3 things : p2p network, public key cryptography and distributed consensus .
The security and accountability of such a system is managed via mass surveillance of transactions and cryptographic evidence. Ensures that blocks are always in chronological order since meddling with the blocks will change the hash for preceding blocks
Verification of block uses ECDSA ( Elliptic Curve Digital Signature Algorithm ) to ensure that tokens are spend by their rightful owners only.
An ellipsis is a derived from the second degree equation like ax^2 + bcy + cy^2 + dx + ey +f =0 . Depending on attributes this could be hyperbola , parabola or even a circle . However elliptic curve cryptography uses a third degree equation from either a pseudo -random curve ( such as over prime fields y^2=x^3+ax+b or binary fields y^2 + xy = x^3 + ax^2 + b ) or a special curve .
what is ECDSA ?
There are 2 types of auth schemes : Symmetric , relying on shared secret key and Asymmetric relying on private public keys . ECDSA is a asymmetric authentication scheme where in addition to sender and receiver , even 3rd party systems can be authenticated . In this the sender uses his private key to sign the message and receiver uses the senders public key to verify the message’s signature .
While publishing a block with pending facts to be appended to a chain , the owner sends it to other nodes for confirmation on its validity. Once its approved , other nodes called miners add it to their copy of chains. However the new block has to be published after fixed time interval for fraud prevention ( example : bitcoin blocks are published every 10 mins on avg ) . This duration is dynamically recalculated as the network miners grow or shrink . A difficulty is a number metric that represents how difficult is it to find a hash for given target.
- To force increase time for calculating the matching hash , difficulty is increased for miners work harder and take longer to earn the block reward .
- While in case of less miner participation , the block difficulty level is made lower