XX% attack and the PoS "timebomb"

Block creators are selected based upon the portion of total stake that they control. Greater stake means greater control. Unlike PoW, 50% stake doesn't mean total control

Attacking PoS requires balancing the needed amount of stake with the duration and success probability of the attack

The PoS timebomb is caused by the fact that, eventually, the users the most stake will have all the stake. Block rewards are proportional to stake size, so the richest grows richer

Key points

Proof-of-Work vs. Proof-of-Stake:

In proof-of-work, a 51 percent attack occurs when someone gains control of the digital ledger by having at least half of the computational resources in the system.

In proof-of-stake, block creators are selected based on the amount of stake they control, not computational resources.

Power in Proof-of-Stake:

In proof-of-stake, the more stake you have, the more power you have on the blockchain. However, having 50 percent of stake resources does not mean total control of the blockchain like in proof-of-work.

Probability of Control in Proof-of-Stake:

With 50 percent of stake resources, you have a 50 percent probability of being selected as the block creator for each block.

This gives you a good chance of receiving block rewards but does not give you complete control.

Short-Term Attacks in Proof-of-Stake:

Short-term attacks in proof-of-stake involve trying to gain control of the blockchain for a specific duration.

The probability of success depends on the percentage of stake resources you control and the desired duration of the attack.

Proof-of-Stake Time-Bomb:

In the long term, the proof-of-stake time-bomb refers to the eventual concentration of stake in the hands of the user with the most stake.

Block rewards are proportional to stake, allowing the richest user to continuously increase their stake and eventually own the entire blockchain.

Conclusion

While proof-of-stake does not provide the same level of control as proof-of-work, it is still possible to perform attacks with a certain probability of success. In the long term, the concentration of stake can lead to complete control of the blockchain by the user with the most stake.