While Proof-of-Work (PoW) requires users to run the hash algorithms multiple times by adding a random alphanumeric string to the block data until the set's fingerprint is below a given threshold, the proof of interest requires the user to prove possession of a certain amount of e-money (their "participation") to claim to validate additional blocks in the blockchain and to receive the reward.
Peercoin was the first cybermoney to use the proof of stake. Other implementations have been attempted using different methods including BitShares, ShadowCash, Nxt, BlackCoin, NuShares / NuBits and Qora. Ethereum has planned a transition from proof of work (PoW) to proof of stake (PoS) in its final deployment. Peercoin and Decred use a hybrid PoW / PoS approach to try to take advantage of both systems and create a more robust consensus.
The main advantage of Proof-of-stake is that it avoids the phenomenal energy expenditure of Proof-of-Work. On the other hand, many people generally believe that the blockchain thus forged does not have the same robustness and the same level of immutability of Bitcoin Proof-of-Work. Some research efforts focus on a hybrid Proof-of-work / Proof-of-stake mechanism
source translate from : bitcoin.fr