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What is Hashing & Digital Signature in The Blockchain? - YouTube
Channel: unknown
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(elegant music)
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- Hi everyone, today we
are going to be talking
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about the word Blockchain
and breaking it down
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to understand what does it mean
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when someone says Blockchains.
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We're gonna take the time to
understand the cryptography
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behind the Blockchain technology.
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So, there are two main
cryptographic concepts
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that underpin Blockchain technology.
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The first, is hashing and the
second is digital signatures.
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So, what is hashing?
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Hashing refers to the concept of
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taking an arbitrary amount of input data,
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applying some algorithm to it
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and generating a fixed size output data
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called the hash.
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The input can be an any number of bits
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that could represent a single character,
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an mp3 file, an entire novel,
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a spreadsheet of your banking history,
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or even the entire internet.
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The point is that the input
can be infinitely big.
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The hashing algorithm can be
chosen depending on your needs
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and there are many publicly
available hashing algorithms.
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The point is that the algorithm
takes the infinite input
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of bits, applies some
calculations to them,
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and outputs a finite number of bits,
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for example, 256 bits.
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So, what can this hash be used for?
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A common usage for hashes
today is to fingerprint files,
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also known as checksums.
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This means that a hash is used to verify
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that a file has not been tampered with
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or modified in any way not
intended by the author.
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So, if wikileaks, for example,
publishes a set of files
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along with their MD5 hashes,
whoever downloads those files
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can verify that they are
actually from wikileaks
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by calculating the MD5 hash
of the downloaded files.
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And, if the hash doesn't match
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what was published by wikileaks
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then you know that file has
been modified in some way.
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So, how does the Blockchain
make use of hashes?
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Hashes are used in
Blockchains to represent
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the current state of the world.
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So, the input is the entire
state of the Blockchain,
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meaning all the transactions
that have taken place so far.
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And, the resulting output hash
represents the current state
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of the Blockchain.
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The hash is used to
agree between all parties
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that the world state is one in the same.
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But how are these hashes
actually calculated?
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The first hash is calculated
for the first Block,
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or the Genesis Block,
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using the transactions inside that Block.
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The sequence of initial
transactions is used to calculate
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a Block hash for the Genesis Block.
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For every new Block that
is generated afterwards,
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the previous Block's hash is also used
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as well as its own transactions
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as input to determine it's Block hash.
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This is how a chain of Blocks is formed.
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Each new Block hash
pointing to the Block hash
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that came before it.
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This system of hashing
guarantees that no transactions
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in the history can be tampered with.
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Because, if any single part
of the transaction changes
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so does that hash of the
Block to which it belongs
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and any following Block's
hashes as a result.
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So, it would be fairly easy to catch
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any tampering as a result.
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Because, you could just
compare the hashes.
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This is cool because
everyone on the Blockchain
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only needs to agree on 256 bits
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to represent the
potentially infinite state
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of the Blockchain.
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The Ethereum Blockchain is
currently 10s of gigabytes.
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But, the current state of the Blockchain,
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as of this recording,
is this hexadecimal has
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representing 256 bits.
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What about digital signatures?
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Digital signatures, like real signatures,
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are a way to prove that somebody
is who they say they are.
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Except that we use cryptography or math
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which is more secure than
handwritten signatures
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that can be easily forged.
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A digital signature is a way to prove
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that a message originates
from a specific person
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and no one else, like a hacker.
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Digital signatures are used
today all over the internet.
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Whenever you visit a website over https,
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you are using SSL which
uses digital signatures
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to establish trust between
you and the server.
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This means that when
you visit Facebook.com
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your browser can check
the digital signature
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that came with the webpage to verify
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that it indeed originated from Facebook
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and not some hacker.
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In asymmetric encryption systems
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users generate something
called a key pair,
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which is a public key and a private key,
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using some known algorithm.
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The public key and
private key are associated
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with each other through some
mathematical relationship.
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The public key is meant
to be distributed publicly
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to serve as an address to
receive message from other users,
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like an IP address or a home address.
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The private key is meant to be kept secret
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and is used to digitally sign
messages sent to other users.
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The signature is included with the message
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so that the recipient can verify
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using the senders public key.
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This way, the recipient can
be sure that only the sender
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could have sent this message.
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Generating a key pair is
analogous to creating an account
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on the Blockchain,
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but without having to
actually register anywhere.
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Pretty cool.
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Also, every transaction that
is executed on the Blockchain
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is digitally signed by the
sender using their private key.
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The signature ensures that
only the owner of the account
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can move money out of the account.
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To bring it all together,
Blockchain could not exist
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without hashing and digital signatures.
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Hashing provides a way for
everyone on the Blockchain
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to agree on the current world state.
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While, digital signatures
provide a way to ensure
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that all transactions are only
made by the rightful owners.
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We rely on these two properties to ensure
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that the Blockchain has not
been corrupted or compromised.
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If you wanna take a deeper dive
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into hashing and digital signatures,
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visit Blockgeeks.com and
read some of our articles
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and guides and our online courses.
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