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Kriptovalute i BitCoin

22.07.2013 20:52 | 13697 Software/Web
Kriptovalute i BitCoin

Nastavljamo editorijal o elektronskom plaćanju, i nakon opšteg uvoda bacamo se na ono zbog čega je ovaj editorijal i nastao – kriptovalute. Pored generalne priče o elektronskom novcu i kriptovalutama, proći ćemo i kroz najosnovnije pojmove iz kriptografije koje je poželjno znati zbog razumevanja funkcionisanja elektronskog novca, ali i kroz decentralizovane kriptovalute kao što je Bitcoin. Potrudili smo se da opise osnovnih koncepata prikaž

Kriptovalute i BitCoin

Ivan Todorović

Da bismo razumeli šta je elektronski novac, moramo prvo imati jasnu sliku o tome šta je uobičajeni novac koji svakodnevno koristimo. Novac je na prvom mestu roba, i to se često kaže da se radi o robi nad robama, koja u „prikrivenom stanju“ u sebi sadrži sve druge robe. Novac je takođe i dogovor, koji može biti dobrovoljan ili prisilan, svestan ili nesvestan, može fluktuirati u vremenu ili biti fiksan.

Sama novčanica predstavlja ugovor, najtvrđu obligaciju kojom se država ili drugi izdavalac obavezuje da donosiocu isporuči robu ili drugu valutu. Novčanica sadrži sve elemente ugovora, kao što su potpis, broj ugovora (to jest broj novčanice), itd. Neke od osnovnih funkcija novca su da služi kao sredstvo za obračun, da predstavlja zajedničku meru vrednosti i jedinicu za razmenu, sredstvo plaćanja, likvidnu imovinu, okvir za tržišnu razmenu, uzročni faktor ekonomije, kontrolor ekonomije itd.


Uopšteno, šta je elektronski novac?

Suština elektronskog novca je da se novac iz fizičke forme pretvori u elektronsku informaciju. U prošlom tekstu pomenuli smo probleme sa fizičkim novcem: proizvodnja, prenos, skladištenje i obezbeđivanje predstavljaju vrlo primetan trošak za banke i finansijske institucije, vreme fizičkog prenosa i cena rada zaposlenih koji nije zanemarivo, i slično.

Elektronski novac se u najširem smislu može definisati kao novac koji se kreće kroz elektronske komunikacione kanale, i to van uobičajenih kanala plaćanja koje banke tradicionalno podržavaju. Banka može da emituje elektronski novac u vidu „brojeva“ koji nose određenu vrednost, ali korisnik u takvom scenariju mora imati račun sa koga će se povlačiti stvarni novac, kao i odgovarajući softver na računaru za komunikaciju sa bankom (makar to bio i običan web browser koji podržava šifrovanu komunikaciju). U slučaju kriptovaluta, kod njih ne postoji centralno telo, odnosno banka koja ih emituje i kontroliše, što je svojevrstan eksperiment koji se do sada pokazao solidno uspešnim.

 

Prednosti elektronskog novca su očigledne: umesto papira, vrednosti se smeštaju u nizove bajtova; e-novac je lako prenosiv kroz mrežu i samim tim ne poznaje granice; može se „programirati“, pratiti i ograničavati, a gubici se nadomešćuju jednostavnom zamenom. Naravno, postoje neki zahtevi koji se moraju ispuniti: mora postojati sigurnost od krađe i falsifikata, e-novac mora biti univerzalno prihvatljiv i naslediti sve dobre osobine tradicionalnog novca, mora biti prenosiv i garantovati privatnost i anonimnost, i naposletku, mora imati neograničeno trajanje i omogućavati denominaciju – plaćanje u razlomljenim iznosima (recimo 125,75 dinara) i sa više novčanica (recimo 1000 dinara kao deset novčanica po sto dinara).

Neki od ovih parametara su u konfliktu: proverljivost i neporecivost se „sudaraju“ sa privatnošću i anonimnošću, dok fizički novac garantuje anonimnost i zato se naročito praktikuje kod poslova „na crno“. Potpunu privatnost jako je teško ostvariti, a i kada bi se ostvarila, postalo bi praktično nemoguće sprečiti „pranje“ novca.


Uticaj elektronskog novca na ekonomiju

Elektronski novac može napraviti jako velik uticaj na ekonomije zemalja. Kada bi se ponašao kao klasičan novac, ne bi bilo problema po državu jer bi ga kontrolisala centralna banka. Međutim, ako se zbog uspešnosti proširi preko granice, koje su posledice? Takođe, ako je privatno emitovan, kako ga učiniti kredibilnim u očima javnosti? Konkurencija banaka može dovesti do toga banka emitent elektronskog novca krene loše da posluje, i tada će svi pokušati da se oslobode njene elektronske valute, što neminovno dovodi do bankrotstva eminenta. Ako već postoji veliki broj korisnika takve elektronske valute, kako u tom slučaju sprečiti paniku?

Svakako, velika efikasnost elektronskog novca dovodi do povećanja rizika monetarne nestabilnosti. Pitanje je da li elektronski novac može biti nezavistan od države. Digitalne kriptovalute koje su danas u upotrebi (recimo Bitcoin) nisu emitovane od strane centralnih banaka i ne predstavljaju prostu digitalnu apstrakciju fizičkog novca (odnosno, plaćanjem kriptovalutama se ne vrši automatsko povlačenje realnih sredstava sa nečijeg računa), zbog čega nemaju čvrstu „zaleđinu“ u vidu nacionalnih valute. Ovo je jedan od razloga njihovih velikih oscilacija vrednosti.

 

sinda Član postova: 1822
Citiram korisnika: ParadigmaYou can broadcast your transaction to the peer nodes that you are connected to, and they can relay that transaction to the peer nodes that they are connected to, and so on until pretty much all nodes on the network have heard about your transaction.  The nodes will store your transaction in their memory pool in case any peer requests it. It won't be "on the blockchain" yet, but some websites might show you the transaction if they have heard about it from any of the nodes they are connected to.Miners (and mining pools) will have heard about the transaction from their connected peers and they can choose to include the transaction in the block that they are working on if they want to. If a miner chooses to include your transaction in their block and they successfully solve the block before any other miners (or pools) solve a block at the same block-height, THEN your transaction is added to the blockchain. The miner broadcasts his block to all his connected peers, and it is relayed throughout the network until nearly everyone has the block with your transaction in their blockchain. When any node sees this new block with your transaction on their blockchain, that node then considers your transaction to be "confirmed".If none of the miners (or pools) choose to include your transaction in any of their blocks, then it won't get confirmed.  Eventually, the nodes on the network will drop your transaction out of their memory pool to make room for newer transactions. There is no specific amount of time that a node is required to remember your transaction.  Some might drop it within a few hours, others might wait a day, some nodes might remember your transaction for a week.  If someone wants to remember the transaction forever, they are welcome to try to do so.Once your transaction has been transmitted, it is view-able by anyone on the network.  That means that anyone can save a copy of it and re-transmit it later if they want.  So if the recipient of your transaction (or anyone else) wants to, they can re-braodcast the transaction every day or so to remind the network and refresh the transaction in the memory of all the nodes.How often YOU re-braodcast the transaction depends on what wallet you are using.  Some wallets (such as Bitcoin Core) will remember all the transactions that they have created, and will re-braodcast the transactions forever trying to remind the network about them so that they eventually get confirmed.  Other wallets (such as blockchain.info) will drop the transaction from their storage after a few days if it hasn't confirmed yet, because they wallet creator assumes that the transaction will never confirm and that most peers have forgotten about it.Transactions are never "returned to the sender".  They are simply forgotten.  If enough of the network has forgotten about your transaction, and your wallet also forgets that you ever sent the transaction, then the wallet will see the bitcoins associated with that transaction as never having been spent and will allow you to create a new transaction that uses those same bitcoins.If you create a new transaction with the same bitcoins, and if the new transaction gets confirmed, then the old unconfirmed transaction will become invalid (since it tries to spend bitcoins that you don't have anymore).  All nodes will then drop the invalid old transaction from their memory and will refuse to accept it from anyone that tries to broadcast it.
Hvala na pojasnjenju. Ja sam,*****,zeznuo stvar sa malim fee...pisao sam i suportu,rekli su ako transakcija ne prodje za 7dana,vraca se nazad,tako da necu nista cackati dok ne prodje tih 7 dana...
riba1990 Novi član postova: 281
ima ko da kupuje btc?
toogood Član postova: 2495
pa jes i za nas
karanovicz Član postova: 1474
Lepa vest za BTC...
Paradigma Moderators postova: 4621
You can broadcast your transaction to the peer nodes that you are connected to, and they can relay that transaction to the peer nodes that they are connected to, and so on until pretty much all nodes on the network have heard about your transaction.  The nodes will store your transaction in their memory pool in case any peer requests it. It won't be "on the blockchain" yet, but some websites might show you the transaction if they have heard about it from any of the nodes they are connected to.
Miners (and mining pools) will have heard about the transaction from their connected peers and they can choose to include the transaction in the block that they are working on if they want to. If a miner chooses to include your transaction in their block and they successfully solve the block before any other miners (or pools) solve a block at the same block-height, THEN your transaction is added to the blockchain. The miner broadcasts his block to all his connected peers, and it is relayed throughout the network until nearly everyone has the block with your transaction in their blockchain. When any node sees this new block with your transaction on their blockchain, that node then considers your transaction to be "confirmed".
If none of the miners (or pools) choose to include your transaction in any of their blocks, then it won't get confirmed.  Eventually, the nodes on the network will drop your transaction out of their memory pool to make room for newer transactions. There is no specific amount of time that a node is required to remember your transaction.  Some might drop it within a few hours, others might wait a day, some nodes might remember your transaction for a week.  If someone wants to remember the transaction forever, they are welcome to try to do so.
Once your transaction has been transmitted, it is view-able by anyone on the network.  That means that anyone can save a copy of it and re-transmit it later if they want.  So if the recipient of your transaction (or anyone else) wants to, they can re-braodcast the transaction every day or so to remind the network and refresh the transaction in the memory of all the nodes.
How often YOU re-braodcast the transaction depends on what wallet you are using.  Some wallets (such as Bitcoin Core) will remember all the transactions that they have created, and will re-braodcast the transactions forever trying to remind the network about them so that they eventually get confirmed.  Other wallets (such as blockchain.info) will drop the transaction from their storage after a few days if it hasn't confirmed yet, because they wallet creator assumes that the transaction will never confirm and that most peers have forgotten about it.
Transactions are never "returned to the sender".  They are simply forgotten.  If enough of the network has forgotten about your transaction, and your wallet also forgets that you ever sent the transaction, then the wallet will see the bitcoins associated with that transaction as never having been spent and will allow you to create a new transaction that uses those same bitcoins.
If you create a new transaction with the same bitcoins, and if the new transaction gets confirmed, then the old unconfirmed transaction will become invalid (since it tries to spend bitcoins that you don't have anymore).  All nodes will then drop the invalid old transaction from their memory and will refuse to accept it from anyone that tries to broadcast it.

Osnove elektronskog plaćanja

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