Blockchain is not Bitcoin, but rather the underlying technology that Bitcoin uses. Blockchain consists of two main components: (1) a protocol that defines rules for how modifications can be made and accepted in a distributed database, and (2) a security mechanism that protects data in the database. The security mechanism involves grouping records into blocks, calculating a hash for each block, and linking blocks together via their hashes to form a chain, making unauthorized changes extremely difficult.

1. Blockchain what is it and what it is not?
I was confused and sometimes still am!
Marco Hauff – Marco.Hauff@gmail.com
What is Blockchain not?
Bitcoin is not blockchain. They
are 2 very separate things.
Bitcoin uses blockchain
technology to operate. You can
compare it a bit to Microsoft
Office uses Microsoft Windows
to run on. You could run Bitcoin
without blockchain and replace it
with something else. The same
as you could run Microsoft
Office of Apple’s IOS
Blockchain is not a database
brand or type. The database that
is used for bitcoin is currently
LevelDB but before that it was
Berkeley DB (Oracle)
What is “blockchain”?
Blockchain is not 1 thing, it is 2 things.
It is a protocol that defines the rules
of how modifications can be made and
accepted to a distributed database
It is a security mechanism that protects
data in a database
In the next pages some further details
on both

2. Blockchain the protocol
If you have multiple instances of databases you need to agree a ruleset ( = protocol)
on how you can add items to a database and then ensure that that addition is
replicated ( read accepted) into the other databases.
You can determine if anyone can add items to the database or a specific group
You can determine what effort / cost is required to add an item to the database. For
example a “ Proof of Work”
You can determine if everyone needs to approve the change or for example a majority

3. Blockchain the Security Mechanism
What you do with block chain is that you do not add records individually to a
database. You group records and once you reached a certain point you add
them in one go. This group is called a block.
To ensure you cannot change any transactions in a block you calculate a hash
algorithm. If you were to change just one character in a record, if would result
into a different hash. At any point in time anyone can validate if the block still
has the same hash, hence if it has not been tampered with.
You can compared hashing by baking a bread. Once you take the bread out of
the oven, you never know how much of each ingredient ( flower, butter, eggs,
etc) went into it. You cannot reverse the process of getting back the flower,
butter and eggs in the original shape. It is very difficult to crack.
What is new with blockchain is that next to hashing the records in the latest
block, you include the hash of the previous block. This way you create a link
( read chain) between every block in the database. This is where the name
blockchain comes from.
So if you wanted to make an unauthorized change to a record in the database,
and ensure that the hashing remained in tact, you would have to recalculate the
exact same hash and then also do this for every block that was created after
that block.
Every block is linked to its predecessor via a hash