# Proof of stake Boo (PoS Boo) PoS Boo is a PoS scheme based on PoS Casper.Th Casper scheme improves the most on “POSv3” with the introduction of a risk factor for malicious stakers. The system is progressive in a way that makes it considerably difficult to execute attacks like the 51% attack; you would need a majority of all minted coins, and you will also face the potential to lose them all when launching such an attack. The finality is mainly determined by stake and risk factors, ## Pros * hard to execute a attack successfully even with 51% of circulation, * solves transaction censoring. With PoW, a block miner can “choose” not to mine a block containing certain addresses, thereby censoring that address from the network. Since block creators are chosen at random and validators are global with this PoS scheme, it is really hard to censor addresses from the network (with the added bonus that if you try to force the network, you will most likely lose your stake). ## Used in * [SHIELD](http://www.shieldx.sh) --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://tokens-economy.gitbook.io/consensus/chain-based-proof-of-stake/proof-of-stake-boo-pos-boo.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.