What's Currency

Currency

Store of value

Unit of account

Exchangable

Now

Issued by authority

NTD

USD

Gash Point

How to issue a currency

Trust

Fluidity

Trust

Decentralize

Encryption Algorithm

Asymmetric cryptography

Hash Function

How to

whisper

Alice Public Key

Bob

Alice

Give me money

Alice Private Key

Encrypt

Decrypt

Problem?

Verification

Double Spent

Resolution

Post 1 dollar to Alice

Bob Private Key

Bob

Alice

Post 1 dollar to Alice

Bob Public Key

Signification

Verification

Katze

👀

Verification

But Signed message is copyable

Resolution

Post 1 dollar to alice

Transection

Serial

1503

Post 15 dollar to alice

Transection

Serial

1504

From

Bob

From

Bob

But serial is predictable or collision. 

Resolution

Post 1 dollar to alice

Transection

Last ID

1f3180a08c80d890f

Post 15 dollar to alice

Transection

Last ID

From

Bob

From

Bob

07215709b70d770c

Hashed

Root Block

Blockchain

Ledger

But this hash too easy

Blockchain

Parent Block

Child Block

Child Block

Child Block

Determine who can write ledger

Resolution

Post 1 dollar to alice

Transection

Last ID

000000a08c80d890f

From

Bob

Nonce

X = ?

Block Hash

X = 1

b9af8ea08c80d890f

X = 2

b8a80b80c9d8e8f0a

X = 3

0a7b879c78978d79f

X = 8692

0000009c78978d79f

Proof of work

Why should user work?

Resolver Earning

Transection Fee

Ledger Writer Reward

Because block size is limited

Reduce by chain long

Dilemma

Proof of Stake

Delegate Proof of Stake

PBFT

Future

Ethereum

Smart Contract

Private Chain