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{{Short description|Scrittrice e ricercatrice venezuelana}} {{Infobox person|name=Gisela Kozak Rovero|image=Gisela Kozak 2013 Baruta Book Festival (cropped).JPG|caption=Kozak al Baruta Book Festival.|birth_name=|birth_date=October 20, 1963|birth_place={{flagicon|Venezuela|1954}} [[Caracas]], Venezuela|death_date=|death_place=|nationality=Venezuelana|alma_mater=Universidad Central de Venezuela|occupation=Scrittrice, saggista, insegnante e ricercatrice|awards=}} '''Gisela Kozak Rovero''' (20 Ottobre 1963) è una scrittrice, saggista, insegnante e ricercatrice venezuelana.<ref name=":0">{{Cite book|last=Parra|first=José Antonio|url=|title=Reflexiones: Angélica Gorodischer, Vol. 2|publisher=Ediciones Nuevo Espacio|year=2002|isbn=1-930879-34-2|editor-last=|___location=New Jersey|page=71-77|language=|chapter=«Gisela Kozak Rovero. Hacia una estética de lo efímero»|access-date=}}</ref>

'''Proof-of-stake''' è un metodo per mettere in sicurezza una rete di [[cryptovalute|Cryptovaluta] e ottenere un consenso distribuito attraverso la richiesta agli utenti di dimostrare la loro proprietà di un certo importo di valuta. E' diverso da un [[proof-of-work system]] che fa girare complessi algoritmi di hashing per convalidare le transazioni elettroniche.<ref>[http://pandacoinpnd.org/proof-of-work-and-proof-of-stake-mining/ Proof-of-Work vs Proof-of-Stake], 31-8-2014</ref> [Peercoin]]<ref name="Peercoin White Paper" /> è stata la prima criptovaluta a lanciare il Proof-of-stake. Altre implementazioni importanti si trovano in [[BitShares]], [[Nxt]], [[BlackCoin]], NuShares/NuBits.

== Educazione e carriera ==

==Varianti a selezione blocco==

Kozak ha cominciato a scrivere all'età di 8 anni, imitando autori come [[Oscar Wilde]] e i [[Fratelli Grimm]]. Si è laureata in letteratura alla [[Università Centrale del Venezuela]] e ha poi conseguito un dottorato alla [[Università Simón Bolívar]].<ref name="qui">{{Cite book|last1=Chacon|first1=Imma|url=|title=15 x 15 mujeres que cuentan en el siglo XXI|last2=Izaguirre|first2=Marian (coord.)|publisher=Maia|year=2009|isbn=9788492724079|___location=|page=|language=|chapter=Gisela Kozak Rovero|author-link=|access-date=}}</ref>

Ogni volta che un blocco viene aggiunto alla blockchain, deve essere selezionato un creatore per quello successivo. Dal momento che non può sempre essere l'account con la maggior parte della valuta (quindi questo creerebbe tutti i blocchi), devono essere escogitati altri metodi di selezione.

Ha lavorato come consigliere alle politiche culturali, come consulente per organizzazioni sia private che pubbliche in Venezuela e come collaboratrice dell'[[Agencia spagnola per la cooperazione]] e il [[Goethe-Institut]] per la formazione di manager culturali. Si è anche impegnata nell'attivismo politico e ha organizzato seminari di saggistica e narrazione alla Literature School e all'ICREA.<ref name=":1">{{Cite news|date=24 June 2013|title=Curriculum|language=es-ES|agency=Gisela Kozak Rovero|url=https://giselakozakrovero.wordpress.com/about/|access-date=12 March 2018}}</ref>

===Selezione casuale del blocco===

[[Nxt]] e [[BlackCoin]] utilizzato la casualizzazione per predire il generatore successivo, usando una formula che cerca il minor valore di hash in combinazione con la dimensione dello stake.<ref name=nxt-whitepaper-blocks /><ref name=nxt-math-of-forging /><ref name="BlackCoin PoS v2 White Paper" /> Visto che gli stake sono pubblici, ogni nodo può prevedere - con accuratezza ragionevole - quale account avrà diritto di creare un nuovo blocco.

E' stata anche un docente invitato alla [[Facoltà Latino Americana di Scienze Sociali]], [[Repubblica Dominicana]], e docente in varie università.<ref name=":1" />

===Selezione basata sull'età della moneta===

Il sistema proof-of-stake di [[Peercoin]] combina la casualizzazione con il concetto di "età della moneta", un numero derivato dal prodotto di un numero di monete per il numero di giorni in cui le monete sono state trattenute. Le monete che non sono state spese per almeno 30 giorni iniziano a competere per il blocco successivo. Insiemi più vecchi e più grandi di monete hanno una probabilità più alta di firmare il blocco successivo. In ogni caso, una volta che le monete sono state usate per firmare un blocco, devono ripartire da "età zero" e quindi attendere almeno altri 30 giorni prima di firmare un altro blocco. Inoltre, la probabilità di trovare il blocco successivo raggiunge il massimo dopo 90 giorni allo scopo di prevenire che collezioni di stake molto vecchie e molto grandi possano dominare la [[Bitcoin#Blockchain|blockchain]]. <ref name="Peercoin White Paper" /><ref>{{cite web|last=Buterin|first=Vitalik|authorlink=Vitalik Buterin|title=What Proof of Stake Is And Why It Matters|url=http://bitcoinmagazine.com/6528/|publisher=Bitcoin Magazine|accessdate=2013-11-20}}</ref><ref>{{cite web|last=Bradbury|first=Danny|title=Third largest cryptocurrency peercoin moves into spotlight with Vault of Satoshi deal|url=http://www.coindesk.com/peercoin-vault-of-satoshi-deal/|publisher=CoinDesk|accessdate=2013-11-20}}</ref> Questo processo rende sicura la rete e gradualmente produce nuove monete nel tempo senza consumare una potenza di calcolo significativa.<ref>{{cite news|last=Thompson|first=Jeffrey|title=The Rise of Bitcoins, Altcoins—Future of Digital Currency|url=http://www.theepochtimes.com/n3/400362-the-rise-of-bitcoins-altcoins-future-of-digital-currency/|accessdate=29 December 2013|newspaper=The Epoch Times|date=15 December 2013}}</ref> Lo sviluppatore di Peercoin dichiara che questo rende gli attacchi intenzionali alla rete più difficili a causa della mancata necessità di mining pool centralizzati e per il fatto che acquistare più della metà delle monete è più costoso che acquisire il 51% della potenza di hashing proof-of-stake.<ref>{{cite news|last=Whelan|first=Karl|title=So What's So Special About Bitcoin?|url=http://www.forbes.com/sites/karlwhelan/2013/11/20/so-whats-so-special-about-bitcoin-2/|newspaper=Forbes|date=2013-11-20}}</ref>

== Pubblicazioni ==

* 1993 ''Rebelión en el Caribe hispánicoː urbes e historias más allá del boom y la posmodernidad'' (Caracas, Ediciones La Casa de Bello) (essay)

's proof-of-stake system combines randomization with the concept of "coin age," a number derived from the product of the number of coins times the number of days the coins have been held. Coins that have been unspent for at least 30 days begin competing for the next block. Older and larger sets of coins have a greater probability of signing the next block. However, once a stake of coins has been used to sign a block, they must start over with zero "coin age" and thus wait at least 30 more days before signing another block. Also, the probability of finding the next block reaches a maximum after 90 days in order to prevent very old or very large collections of stakes from dominating the [[Bitcoin#Blockchain|blockchain]]. <ref name="Peercoin White Paper" /><ref>{{cite web|last=Buterin|first=Vitalik|authorlink=Vitalik Buterin|title=What Proof of Stake Is And Why It Matters|url=http://bitcoinmagazine.com/6528/|publisher=Bitcoin Magazine|accessdate=2013-11-20}}</ref><ref>{{cite web|last=Bradbury|first=Danny|title=Third largest cryptocurrency peercoin moves into spotlight with Vault of Satoshi deal|url=http://www.coindesk.com/peercoin-vault-of-satoshi-deal/|publisher=CoinDesk|accessdate=2013-11-20}}</ref> This process secures the network and gradually produces new coins over time without consuming significant computational power.<ref>{{cite news|last=Thompson|first=Jeffrey|title=The Rise of Bitcoins, Altcoins—Future of Digital Currency|url=http://www.theepochtimes.com/n3/400362-the-rise-of-bitcoins-altcoins-future-of-digital-currency/|accessdate=29 December 2013|newspaper=The Epoch Times|date=15 December 2013}}</ref> Peercoin's developer claims that this makes a malicious attack on the network more difficult due to the lack of a need for centralized mining pools and the fact that purchasing more than half of the coins is likely more costly than acquiring 51% of proof-of-work hashing power .<ref>{{cite news|last=Whelan|first=Karl|title=So What's So Special About Bitcoin?|url=http://www.forbes.com/sites/karlwhelan/2013/11/20/so-whats-so-special-about-bitcoin-2/|newspaper=Forbes|date=2013-11-20}}</ref>

* 1997 ''Pecados de la capital y otras historias'' (story)

* 1998 ''La catástrofe imaginaríaː cultura, saber, tecnología, instituciones'' (Caracas, Planeta-Celarg)(essay)

* 1999 ''Rapsodia'' (novel)

* 2003 ''Vida de machos'' (novel)

* 2006 ''Latidos de Caracas'' (Caracas: Alfaguara) (novel)

* 2007 ''Venezuela, el país que siempre naceː literatura, política y pasión de historia'' (Caracas: Alfadil) (essay)

* 2011 ''En rojo, narración coral'' (Caracas: Alfa) (stories)

* 2011 ''Todas las lunas'' (Caracas: Equinoccio) (novel)<ref name="roc">{{Cite journal|title=Gisela Kozak hace de la narrativa transgenérica su propia aventura|url=http://impresodigital.el-nacional.com/ediciones/favoritos/archive/result_archive.asp?a=2012&m=03&d=09&filename=n8_3n1.asp&searchstring=|journal=El Nacional|archive-url=https://web.archive.org/web/20170406111303/http://impresodigital.el-nacional.com/ediciones/favoritos/archive/result_archive.asp?a=2012&m=03&d=09&filename=n8_3n1.asp&searchstring=|archive-date=6 April 2017|access-date=5 April 2017}}</ref>

* 2012 ''Literatura asediada: revoluciones políticas, culturales y sociales'' (investigation)

* 2014 ''Ni tan chéveres ni tan iguales. El «cheverismo» venezolano y otras formas del disimulo'' (essay)

* 2017 ''Siete sellos: crónicas de la Venezuela Revolucionaria'' (compiler)

Kozak has also published several articles in national and international specialized magazines, compilations and congresses memories.<ref>{{Cite web|last=|author-link=|date=|editor-last=Fundación Dialnet|title=Gisela Kozak Rovero. Artículos de revista|url=http://dialnet.unirioja.es/servlet/autor?codigo=752908|access-date=14 September 2015|website=Dialnet|publisher=Dialnet|language=}}</ref>

===Velocity Based Selection===

[[Reddcoin]]'s 'Proof of Stake Velocity' (PoSV)<ref name="Reddcoin PoSV White Paper">{{cite web|last=Ren|first=Larry|title=Proof of Stake Velocity: Building the Social Currency of the Digital Age|url=http://www.reddcoin.com/papers/PoSV.pdf}}</ref> claims to encourage velocity i.e. movement of money between people, rather than hoarding.

== Awards and recognitions ==

===Voting Based Selection===

Instead of only using the stake size, the block generators can be selected by votes. [[BitShares]] uses a system of 101 delegates and selects randomly among these.<ref name=bitshares-dpos>{{cite web|title=BitShares - Delegated Proof of Stake|url=http://bitshares.org/documentation/group__dpos.html|website=bitshares.org|accessdate=2 January 2015}}</ref> The community votes enhance the incentives of the generators to act responsibly, while on the downside opening the door for [[sybil attack]]s - as in the case where one user posed as the top five delegates.<ref name=bitshares-sybil-attack>{{cite web|title=BitShares Sybil Attack Discussion|url=https://bitsharestalk.org/index.php?topic=10937.0|website=bitsharestalk.org|accessdate=2 January 2015}}</ref>

* 1997 Premio ''Armas Alfonzo'' por ''Pecados de la capital Biennial'' Award

==Advantages and Disadvantages==

* 1999 DAAD Intern in Germany

Proof of Work relies on energy use. That means an external tangible good is providing the security. On the down-side, this leads to a race towards burning more and more energy. By account of a Bitcoin mining-farm operator these were 240kWh per Bitcoin in 2014 (the equivalent of 16 gallons of gas).<ref name=bitcoin-carbon-footprint /> Proof of Stake currencies can be several thousand times more cost effective.<ref name=costefficiency /> These mining costs have to flow out of the currency - putting a downward pressure on the price.

* 1999 ''Miguel Otero Silva'' Award Finalist (Editorial Planeta, for ''Latidos de Caracas)''

* 2003 SACVEN Story Contest finalist (for ''Vida de machos'')

* 2006 ''Enrique Bernardo Nuñez Essay Bienniel'' honorary mention [[Valencia, Carabobo|Valencia]] Athenaeum (for ''Venezuela, el país que siempre naceː literatura, política y pasión de historia'')

* 2009 Sylvia Molloy Award to the best academic article about gender and sexuality, awarded by the [[Latin American Studies Association]] (LASA, USA-Canada, for the article «El lesbianismo en Venezuela es asunto de pocas páginas»)

* 2012 Critic Award finalist (for the novel ''Todas las lunas'')

== Personal life ==

One aspect are the incentives that are very different. Proof-of-Work means that the generator is not necessarily holding the currency. The incentive is to maximize returns from the hardware. There is a discussion whether this lowers or raises security risks.<ref name=pow-pos-debate>{{cite web|title=Proof of Work, Proof of Stake and the Consensus Debate|url=http://cointelegraph.com/news/113157/proof-of-work-proof-of-stake-and-the-consensus-debate|website=cointelegraph.com|accessdate=3 January 2015}}</ref> In Proof-of-Stake the coin owner and coin guard are the same. Though several cryptocurrencies allow or enforce lending the staking power to other nodes.

Kozak is openly lesbian.<ref>{{Cite web|last=Sánchez|first=Matilde|date=7 May 2021|title=G. Kozak: Venezuela, el país sin libros|url=https://www.clarin.com/revista-enie/gisela-kozak-noticias-pais-libros_0_tdHNDXQk9.html|url-status=live|access-date=18 June 2021|website=[[Clarín (Argentine newspaper)|Clarín]]|language=es}}</ref><ref>{{Cite web|date=1 January 1970|title=Soy lesbiana. Punto.|url=https://www.fundacionreflejosdevenezuela.com/mujer-y-punto/soy-lesbiana-punto/|access-date=18 June 2021|website=Radio Reflejos}}</ref><ref>{{Cite web|date=10 July 2019|title=Lesbianas visibles e invencibles|url=https://literalmagazine.com/lesbianas-visibles-e-invencibles/|access-date=18 June 2021|website=Literal Magazine|language=en-US}}</ref>

==Criticism==

Some authors<ref name="apoelstra">{{cite web|title=Distributed Consensus from Proof of Stake is Impossible|url=https://download.wpsoftware.net/bitcoin/pos.pdf|author=Andrew Poelstra}}</ref><ref name=buterin-on-stake /> argue that proof-of-stake is not an ideal option for a distributed consensus protocol. The main problem is usually called the "nothing at stake" problem. It means that in case of a chain fork (or any other kind of consensus disagreement), a person can "vote" for both variants, because he has a stake in each branch. There is little cost in working on several chains (unlike in proof-of-work systems), and that gives the ability to try to cheat (e.g. double-spend in case of blockchain reorganization) "for free".<ref>{{cite web|title=Hard Problems of Cryptocurrencies|url=https://github.com/ethereum/wiki/wiki/Problems}}</ref>

Many have attempted to solve these problems:

* Peercoin uses centrally broadcast checkpoints ([[Digital signature|signed]] under the developer's [[private key]]). No blockchain reorganization is allowed deeper than the last known checkpoints. The tradeoff is that the developer is the central authority controlling the blockchain.

* [[Nxt]]'s protocol only allows to reorganize last 720 blocks.<ref name=nxt-whitepaper=history-attacks>{{cite web|title=Nxt Whitepaper: History Attack|url=https://wiki.nxtcrypto.org/wiki/Whitepaper:Nxt#History_Attack|website=Nxtwiki|accessdate=2 January 2015}}</ref> Disallowing blockchain reorganizations can cause your client to follow a fork of 721 blocks regardless of whether it is the tallest blockchain, preventing consensus.

* [[Ethereum]]'s suggested Slasher protocol allows users to "punish" the cheater, who mines on the top of more than one blockchain branch.<ref>{{cite web|last1=Buterin|first1=Vitalik|title=Slasher: A Punitive Proof-of-Stake Algorithm|url=https://blog.ethereum.org/2014/01/15/slasher-a-punitive-proof-of-stake-algorithm/}}</ref> This proposal assumes you must double-sign to create a fork and that you can be punished if you create a fork while not having stake.

Statistical simulations have shown that simultaneous forging on several chains is possible, even profitable. But Proof of Stake advocates believe most described attack scenarios are impossible or so unpredictable that they are only theoretical.<ref name=pos-security-issues /><ref name=multibranch-forging />

==See also==

* [[Proof-of-work system|Proof of Work]]

* [[Bitcoin]]

* [[Nxt]]

* [[Peercoin]]

* [[BlackCoin]]

==References==

<references />

{{Reflist|30em| refs=

<ref name="Peercoin White Paper">{{cite web|last=King|first=Sunny|title=PPCoin: Peer-to-Peer Crypto-Currency with Proof-of-Stake|url=http://www.peercoin.net/assets/paper/peercoin-paper.pdf|accessdate=2014-11-17}}</ref>

<ref name="BlackCoin PoS v2 White Paper">{{cite web|last=Vasin|first=Pavel|title=BlackCoin’s Proof-of-Stake Protocol v2|url=http://www.blackcoin.co/blackcoin-pos-protocol-v2-whitepaper.pdf}}</ref>

<ref name=nxt-whitepaper-blocks>{{cite web|title=Nxt Whitepaper (Blocks)|url=https://wiki.nxtcrypto.org/wiki/Whitepaper:Nxt#Blocks|website=nxtwiki|accessdate=2 January 2015}}</ref>

<ref name=bitcoin-carbon-footprint>{{cite web|title=Carbon Foodprint of Bitcoin|url=http://www.coindesk.com/carbon-footprint-bitcoin/|website=coindesk.com|accessdate=2 January 2015}}</ref>

<ref name=costefficiency>{{cite web | url=http://cfa-consulting.ch/dlfiles/NxtEnergyandCostEfficiencyAnalysis.pdf | title=Nxt Network Energy and Cost Efficiency Analysis|accessdate=21 December 2014}}</ref>

<ref name=nxt-math-of-forging>{{cite web|last1=mthcl (pseudonymous)|title=The math of Nxt forging|url=http://www.docdroid.net/file/view/e29h/forging0-5-1.pdf|website=pdf on docdroid.net|accessdate=22 December 2014}}</ref>

<ref name=multibranch-forging>{{cite web|last1=Chepurnoy|first1=Alexander|title=PoS forging algorithms: formal approach and multibranch forging|url=https://www.scribd.com/doc/248208963/Multibranch-forging|website=scribd.com|accessdate=22 December 2014}}</ref>

<ref name=pos-security-issues>{{cite web|last1=Chepurnoy|first1=Alexander|title=PoS forging algorithms: multi-strategy forging and related security issues|url=https://github.com/ConsensusResearch/articles-papers/raw/master/multistrategy/multistrategy.pdf|website=github.com|accessdate=30 December 2014}}</ref>

== External links ==

<ref name=buterin-on-stake>{{cite web|url=https://blog.ethereum.org/2014/07/05/stake/|author=Vitalik Buterin|title=On Stake}}</ref>

* [https://giselakozakrovero.wordpress.com/me-presentoescribo-y-leo// Gisela Kozak's Blog]

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