hi in this video we will get an
introduction to blockchain which is the
technology that crypto currencies like
Bitcoin are based on blockchain is based
on a concept called proof of work
basically if you want to get paid any
kind of cryptocurrency
you have to prove you have worked on the
blockchain through a transaction of some
kind so what is this blockchain well a
blockchain is a digital ledger in which
transactions made in something like
Bitcoin or another cryptocurrency are
recorded chronologically and publicly we
can actually look at a blockchain and
see evidence or proof of what has
happened or what is going on this
evidence in the ledger is our proof of
work a blockchain is really no more than
a distributed database that utilizes a
very large network of computing devices
think of it as a large worldwide
computer where everyone can securely
access data and execute transaction code
all transactions are stored in blocks of
data a ledger is a list of transactions
or exchanges that usually includes
information about the transactions such
as the date what was purchased amounts
etc block chains are also immutable if
you find an error on your bank statement
like an extra charge the bank can't
remove that charge instead the bank
refunds your money in a regular ledger
if someone modifies one entry it has no
impact on the other entries when you
mutate something you change it like the
amount above that was originally 1,500
it was changed to 2,000 this cannot
happen in a blockchain immutable means
you can't change it block chains are
immutable blocks in a blockchain are
made in such a way that it makes them
very hard to manipulate or fake once
they are stored to the blockchain
because if someone modifies an entry or
transaction it instantly invalidates all
of the later entries blockchain makes it
harder to tamper with ledger
transactions and easier to detect
tampering should it occur in order to
accomplish this it uses something called
a hash
a hashes of value produced by hashing
function in computer programming so
cryptography is the practice of encoding
information so only authorized people
can read it hashing is one of these
types of cryptography that we can use to
make data secure and it's the foundation
for making block chains hashing in a
blockchain changes a transaction into an
unreadable string of text for the
purpose of encrypting the transaction as
we'll see hashing is perfectly suited
for block chains a cryptographic hash
function is a one-way function that
takes input data of some arbitrary
length and produces a fixed sized output
so the hash is always the same size that
the hash function tells it to be
regardless of how big the input is the
hash is a lot smaller than the data
itself and it's generated by a
mathematical formula inside of a
computer program in such a way that it's
really unlikely that some other text
would produce that same hash value
hashing algorithms and block chains take
a chunk of transaction data and hash it
the cool thing about hash data is that
the computation is much simpler going
forwards than backwards so it's easy to
confirm we get an output hash that
usually looks like nonsense as shown but
it will always be the same length no
matter how big our input was making good
one-way hash functions and block chains
relies on some math to produce these
random strings of letters and numbers s
hash output we won't get into the math
instead we'll use a simple online hash
generator the most used hashing
algorithms are generally very well known
and available to the public if very
common hashing algorithm used with
blockchain technology is sha-256 it is
one of several hashing algorithms and it
will produce a long text string as a
result so let's jump out to a sha-256
hash generator this is a really simple
hash generator where you can enter any
kind of text and see what kind of hash
is actually generated below so let's
let's say I type in the word code HS
notice I get a hash of that string it's
8 d 0 0 9 2 6
and so forth so it's a string of letters
and numbers this is my hashed output if
I remove just a single letter the letter
S look how drastically my hash changes
zero to eight one eight seven two blah
blah so just changing the input even
slightly changes the entire hash output
so I put the s back on I still get the
same original input eight D zero zero
nine six two so any given input should
always produce the exact same hash
output but just changing the input ever
so slightly will completely change the
hash output and that's what a good hash
generator or hash algorithm should do
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