#Security (subpage)

Network security is a critical foundation for any financial system. Agreement on transactions and account balances, also known as consensus, it vital to confidence in the currency and can be measured by both longevity and by analysis of its resistance to various attack vectors.

In peer-to-peer financial systems, Proof-of-Work solved the double spending problem. It has proved its worth for more than a decade, but it is energy intensive and susceptible to majority attacks. Proof-of-Stake was developed to avoid those issues through alignment of interests, but it came with its own shortcomings, most notably the nothing at stake problem.

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Proof-of-Work
An Imperfect Solution
•Energy & machine intensive
•51% attacks: Re-write history, enable theft of funds

Proof-of-Stake
•Nothing at stake: Stakers can forge multiple chains
•Crypto derivatives: Shorting incentivizes bad behavior
•Feudalistic: Stakers maintain their relative wealth
•More centralized: Fewer network participants
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###Decredʼs Hybrid Solution
Decred employs a combination of PoW and PoS to yield the best of both systems,
mitigate their weaknesses, and deliver a layered consensus mechanism that
makes it far more secure than other cryptocurrencies. Decred uses conventional PoW,
typically mined by ASICs using the Blake-256 hash algorithm, for which it is
dominant. Decred holders time-lock their funds to purchase tickets. Those tickets are added to a pool of roughly 41,000 tickets, and five tickets are pseudorandomly selected to validate the proof-of-work for each block. If at least 50% of the tickets approve the work of the miner, the block is approved and added to the blockchain.

####Resistance to Attacks

Because a block must include 3 or more ticket votes to be valid, miners cannot mine in secret.  The result is that an attacker must have considerable hashpower and stake to successfully execute a majority attack.  When comparing the cost of an attack on Decred to that of a pure PoW cryptocurrency, the cost to attack Decred is an order of magnitude greater, plus any attacker with stake would be taking actions counter to their interests.