A very brief presentation for our Cryptography class at #MelbourneUniversity on several proof mechanisms to secure block chain in Cryptocurrencies.

1. PROOFS ON CRYPTO
CURRENCIES
PABLO SERRANO
IVAN SANCHEZ

2. PROOF OF STAKE
• Also helps to secure the network.
• Proposed by King and Nadal in 2012
• Based on Coin Age: Combination of Amount of currency owned and the time
held.
• Coin Age is a measure in
• determining staking weight and
• Probability of a PoS coin holder winning a block.
• PoS is a Form of proof of ownership of the currency.
• Coin age can be considered a form of PoS
• PoS cannot be easily forged (key requirement of monetary systems).
• PoS block mints coins based on the consumed coin age in the coinstake
transaction.

3. BLOCK SIGNATURE & DUPLICATE STAKE
PROTOCOL
• Each block must be signed by owner to prevent replay attacks.
• Duplicate-stake protocol defends against attackers using a
single PoS to generate multiple blocks as a DoS Attack.

4. HASHING
• Input of Coinstake:
• Kernel: Required to meet certain hash target protocol.
• The hashing operation is done over a limited search space.
• Hash target that stake Kernel must meet is a target per unit
coin age (coin-day).

5. MAIN CHAIN PROTOCOL
• Protocol for determining the main chain relies on coin-age.
• Every transaction in a block contributes its consumed coin age to the
score or the block.
• Block with highest consumed coin age is the main chain

6. DIFFERENCES WITH POW
• As opposed to Proof of Work (Pow)
• Lower computational cost & more energy efficient (less
environmental costs)
• Lower entry barrier for newcomers
• Main chain is determined by total consumed coin age and not by total
work of block.
• Cost of controlling significant stake might be higher tan cost of
acquiring mining power.
• When PoW mint rate approaches 0, there is less incentive to mint
blocks. If energy consumption reaches 0, protection for PoW decays.
PoS is immune to this.

7. PROBLEMS
• First PoS eliminates competitive model that incentivized users
to participate actively (active nodes) in Network maintenance.
• Some coin holders accrued interest without contributing to
secure the network.
• Lower cost of attacks on the entire blockchain (due to total
consumed coin age main chain determinism method).
• No completely distributed, some centralized checkpoints are
needed to secure block chain.

8. OTHER VARIATIONS
• Eliminate Coin Age (PoS 2.0)
• Proof of Stake Velocity (PoSV): Reward active participants and
punish infrequent stakers (Give big reward to those who win
blocks every 2 weeks)
• Proof of Stake: Definite (PoS:D). Replaces interest based stake
reward system with a inflationary system of constant rewards.
• Ensures that a set amount of coins are issued each block.