This document provides an overview of blockchain technology, bitcoin, hashing, and digital signatures. It defines blockchain as a growing list of transaction records linked using cryptography. Blockchains typically contain financial transactions that are replicated across peer-to-peer networks and use cryptography to prove identity and access rights. Bitcoin is described as a virtual currency where a record of coin ownership is kept instead of physical money. The document also summarizes hashing, proof of work, Hyperledger, and how digital signatures authenticate messages.

1. Blockchain Technology,
Bitcoin, Hashing and Digital
signature
BY:-
ANIL CHAURASIYA
SCHOOL OF COMPUTER & INFORMATION
SCIENCES (SCIS)
UNIVERSITY OF HYDERABAD
HYDERABAD
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2. contents
 What is Blockchain
 Blockchain contains
 Example of services using Blockchain
 What is Bitcoin
 Features of Bitcoin
 Decetralization in Bitcoin
 Hyperledger
 Hashing
 Proof of work
 Digital signature
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3. What is Blockchain
A blockchain is a continuously growing
list of records, called block, which are
linked and secured using
cryptography. Each block typically
contains a hash pointer as a link to a
previous block, a timestamp and
transaction data.
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4. Blockchain contains
 Usually contains financial transactions.
 Is replicated across a number of systems in
almost real-time.
 Usually exists over a peer-to-peer network.
 Uses cryptography and digital signatures to
prove identity, authenticity and enforce
read/write access rights.
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5. Examples of services using
blockchain
 Finance
 Point/Reward
 Communication
 Authentication
 Medical
 Public sector
 IoT
 Future prediction
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6. What is Bitcoin
Bitcoin is a virtual currency. Instead
of printing banknotes, or minting coins, a
list of the registration numbers of each of
the "coins" is kept and a record of who
owns them. People can pay one another by
transferring the registration numbers
online.
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7. Features of Bitcoin
 Bitcoin infinitely divisible currency units
supporting eight decimal places 0.00000001.
 No central authority.
 Cannot be double-spent.
 Non-repudiation – no recourse and no one to
appeal to return sent tokens.
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8. Decentralization in Bitcoin
 The “digital wallet” operates in a peer to peer
mode
 The wallet will synchronize with the network
by downloading ALL of the transactions
starting from the GENESIS block.
 Using a “gossip protocol” the wallets share all
transaction information with their peers.
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9. Bitcoins flow from Inputs to
Outputs
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10. Hyperledger
Hyperledger is an open source blockchain platform, started
in December 2015 by the Linux Foundation, to support
blockchain-based distributed ledgers. It is focused on
ledgers designed to support global business transactions,
including major technological, financial, and supply chain
companies, with the goal of improving many aspects of
performance and reliability. The project aims to bring
together a number of independent efforts to develop open
protocols and standards, by providing a modular framework
that supports different components for different uses.
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11. Hashing
 A hash function is used to map digital data of arbitrary size
to digital data of fixed size, with slight differences in input
data producing very big differences in output data.
 MD5, SHA1, SHA256
 For example, the MD5 hashes of ‘abc’ compared to ‘abC’
abc
0bee89b07a248e27c83fc3d5951213c1
abC
2217c53a2f88ebadd9b3c1a79cde2638
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12. Hashing
 Hashing is straightforward, but not challenging
 Unless the goal is to say, find me a hash value that
satisfies a certain level of “difficulty”
 For example, let’s say the challenge is find a hash-value
that begins with a number of zeros, for a given input
 The Proof of Work comes from finding a number
(known as a NONCE) that when added to the input
changes the output of the hash value to satisfy the
difficulty.
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13. Proof of Work
 A publicly auditable cost-function can be efficiently verified
by any third party without access to any trapdoor or secret
information.
 A fixed cost cost-function takes a fixed amount of resources to
compute. The fastest algorithm to mint a fixed cost token is a
deterministic algorithm.
 A probabilistic cost cost-function is one where the cost to the
client of minting a token has a predictable expected time, but a
random actual time as the client can most efficiently compute
the cost-function by starting at a random start value.
Sometimes the client will get lucky and start close to the
solution.
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14. Consensus achieved using Proof
of work
 New transactions are broadcast to all nodes.
 Each node collects new transactions into a block.
 Each node works on finding a difficult proof-of-work for its
block.
 When a node finds a proof-of-work, it broadcasts the block to
all nodes.
 Nodes accept the block only if all transactions in it are valid
and not already spent.
 Nodes express their acceptance of the block by working on
creating the next block in the chain, using the hash of the
accepted block as the previous hash.
 Nodes always consider the longest chain to be the correct one
and will keep working on extending it.
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15. Purchase / Exchange Bitcoins
In addition to mining bitcoins, they can be acquired from an
exchange!
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16. Who Accepts Bitcoins?
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17. Merchants Accepting Bitcoin
Overstock.com
Newegg.com
Microsoft XBOX Network
Telsa Motors
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18. Digital Signature
Digital signature is an electronic signature that can be used
to authenticate the identity of the sender of a message or the
signer of a document, and possibly to ensure that the
original content of the message or document that has been
sent is unchanged. Digital signatures are easily
transportable, cannot be imitated by someone else, and can
be automatically time-stamped. The ability to ensure that the
original signed message arrived means that the sender
cannot easily repudiate it later.
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19. How digital signature works
The use of digital signatures usually involves two processes, one
performed by the signer and the other by the receiver of the digital
signature:
 Digital signature creation uses a hash result derived from and
unique to both the signed message and a given private key. For
the hash result to be secure, there must be only a negligible
possibility that the same digital signature could be created by
the combination of any other message or private key.
 Digital signature verification is the process of checking the
digital signature by reference to the original message and a
given public key, thereby determining whether the digital
signature was created for that same message using the private
key that corresponds to the referenced public key.
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20. How digital signature works
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