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Quote from: irukandji on March 18, 2017, 09:08:45 PM

When Dash transactions get locked (to enable fast transactions and prevent double spending), who or what is in control of the "locking"?
Thanks

A set of 10 (pseudo-) randomly, but deterministically selected Masternodes.

Thank you. You're probably not totally surprised

, that that sounds a tad confusing.

So they are randomly selected but there is a deterministic component too? Huh

It's based on the blockhash from the proofofwork for a block, and those hashes cannot be predicted before the block is mined, That's the random component.
Once a block is found, this hash and some other (Masternode-) attributes are used to compute the 10 Masternodes responsible for locking. This is the deterministic component.

Thanks again. So there is a bias towards certain MN's?
If so what are these attributes?

thanks

Quote

InstantSend (formerly InstantX) Transactions in Dash version 12 are secured using a consensus of deterministically selected masternodes. This set of masternodes is informally termed quorum and must be in a majority agreement, at least six out of ten, for a successful lock of the transaction inputs.

Quorums are self-selected on a per-transaction basis using a combination of three elements: Transaction Age, Block Height, and Masternode Funding Transaction.

Transaction Age

When an InstantSend transaction is broadcast, the age of the first unspent input in the transaction influences which proof of work hash to use as entropy for quorum selection. All InstantSend inputs must be at least six blocks old or the transaction will be rejected.

Block Height

The age of the first InstantSend input is then subtracted from the current blockchain height. To prevent using transaction malleability to influence quorum selection, four is then added to the calculated block height to guarantee choosing a block generated after the input was created.

Masternode Funding Transaction

Each masternode receiving the InstantSend transaction lock request then compares the hash of its funding transaction to the hash of the block calculated above. After validating the inputs are not spent, the top ten masternodes closest to this proof of work hash broadcast their acceptance of the lock.

https://dashpay.atlassian.net/wiki/display/DOC/Quorum+Selection

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