MapleStory

simple cryptography tools in blockchain

Hash Function

takes any string as input
fixed-sized output(usually 256 bits)
efficiently computable

security properties:

collision-free
hiding
puzzle-friendly

SHA-256

Hash Pointer

Merkle Tree

Digital signature scheme

Only you can sign, but anyone can verify

  • (sk, pk) := generateKeys(keysize)
  • sig := sign(sk, message)
  • isValid := verify(pk, message, sig)

    Public keys as Identities

    A useful trick as Bitcoin do

A Simple Cryptocurrency Example

  • GoofyCoin
    1.Goofy, can create new coins whenever he wants and these newly created coins belong to him
    2.whoever owns a coin can transfer it on to someone else

    double‐spending attack — Alice is spending the same coin twice.
  • ScroogeCoin
    Scrooge publishes an append‐only ledger containing the history of all the transactions that have happened.
    ScroogeCoin block chain.

    CreateCoins transaction.

    A PayCoins Transaction.

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