Jorge Stolfi (born 1950 in

São Paulo São Paulo (, ; Portuguese for 'Saint Paul') is the most populous city in Brazil, and is the capital of the state of São Paulo, the most populous and wealthiest Brazilian state, located in the country's Southeast Region. Listed by the GaWC a ...

) is a

full professor Professor (commonly abbreviated as Prof.) is an academic rank at universities and other post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin as a "person who professes". Professors ...

computer science Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical discipli ...

at the

State University of Campinas The State University of Campinas ( pt, Universidade Estadual de Campinas), commonly called Unicamp, is a public research university in the state of São Paulo, Brazil. Unicamp is consistently ranked among the top universities in Brazil and Latin ...

, working in

computer vision Computer vision is an interdisciplinary scientific field that deals with how computers can gain high-level understanding from digital images or videos. From the perspective of engineering, it seeks to understand and automate tasks that the hum ...

image processing An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimensiona ...

, splines and other

function approximation In general, a function approximation problem asks us to select a function among a that closely matches ("approximates") a in a task-specific way. The need for function approximations arises in many branches of applied mathematics, and compute ...

methods,

graph theory In mathematics, graph theory is the study of ''graphs'', which are mathematical structures used to model pairwise relations between objects. A graph in this context is made up of '' vertices'' (also called ''nodes'' or ''points'') which are conne ...

computational geometry Computational geometry is a branch of computer science devoted to the study of algorithms which can be stated in terms of geometry. Some purely geometrical problems arise out of the study of computational geometric algorithms, and such problems ar ...

and several other fields. According to the ISI Web Of Science, he was the most highly cited computer scientist in Brazil. Outside of academia, Stolfi has accrued an online following due to his skepticism and comments on Bitcoin.

Early life and career

Jorge Stolfi was born in

Vila Carrão Vila Carrão () is the historical name of a small residential neighborhood in São Paulo, with 75,000 residents as of 2005. It belongs to the Carrão district and to the Aricanduva sub-prefecture. Vila Carrão is located about 13 km east o ...

, a suburb of

. His parents had immigrated to Brazil from the

Veneto Veneto (, ; vec, Vèneto ) or Venetia is one of the 20 regions of Italy. Its population is about five million, ranking fourth in Italy. The region's capital is Venice while the biggest city is Verona. Veneto was part of the Roman Empire unt ...

region of

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...

only two years earlier, and so he spoke Venetian as his first language. He obtained an

engineering degree An engineer's degree is an advanced academic degree in engineering which is conferred in Europe, some countries of Latin America, North Africa and a few institutions in the United States. The degree may require a thesis but always requires a non-a ...

electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

(1973) and

M.Sc. A Master of Science ( la, Magisterii Scientiae; abbreviated MS, M.S., MSc, M.Sc., SM, S.M., ScM or Sc.M.) is a master's degree in the field of science awarded by universities in many countries or a person holding such a degree. In contrast to ...

applied mathematics Applied mathematics is the application of mathematical methods by different fields such as physics, engineering, medicine, biology, finance, business, computer science, and industry. Thus, applied mathematics is a combination of mathematical s ...

(1979) from the

University of São Paulo The University of São Paulo ( pt, Universidade de São Paulo, USP) is a public university in the Brazilian state of São Paulo. It is the largest Brazilian public university and the country's most prestigious educational institution, the best ...

. From 1979 to 1988 he was a student of Leo Guibas at

Stanford University Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is consider ...

, where he got a

Ph.D A Doctor of Philosophy (PhD, Ph.D., or DPhil; Latin: or ') is the most common Academic degree, degree at the highest academic level awarded following a course of study. PhDs are awarded for programs across the whole breadth of academic fields ...

in computer science. He had a

CNPq The Brazilian National Council for Scientific and Technological Development (CNPq, pt, Conselho Nacional de Desenvolvimento Científico e Tecnológico, earlier ) is an organization of the Brazilian federal government under the Ministry of Scien ...

grant from 1979 to 1983, then a research internship at

Xerox PARC PARC (Palo Alto Research Center; formerly Xerox PARC) is a research and development company in Palo Alto, California. Founded in 1969 by Jacob E. "Jack" Goldman, chief scientist of Xerox Corporation, the company was originally a division of Xero ...

until 1985, and also at the DEC Systems Research Center (SRC) until 1988. After obtaining his Ph.D. he became a research engineer at SRC. In 1992 he returned to Brazil to take a position at the Computer Science Department of the

University of Campinas The State University of Campinas ( pt, Universidade Estadual de Campinas), commonly called Unicamp, is a public research university in the state of São Paulo, Brazil. Unicamp is consistently ranked among the top universities in Brazil and Latin ...

(UNICAMP), which later became the university's Institute of Computing. He was the institute's chairman from 2004 to 2008.

Research

While at Stanford, Leo Guibas and Jorge worked on the then-new field of

. Among other results they developed the

quad-edge A quad-edge data structure is a computer representation of the topology of a dimension, two-dimensional or three-dimensional CW complex, map, that is, a graph theory, graph drawn on a (closed) Surface (topology), surface. It was first described by ...

data structure for two-dimensional maps, the kinetic framework for computational geometry. Jorge's Ph.D. dissertation on oriented projective geometry was later published as a book.
From original

Stanford Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is considere ...

Ph.D. dissertation, ''Primitives for Computational Geometry'', available a
DEC SRC Research Report 36
published by HP Labs. Accessed 2010-12-28. He also drew dozens of

cartoons A cartoon is a type of visual art that is typically drawn, frequently animated, in an unrealistic or semi-realistic style. The specific meaning has evolved over time, but the modern usage usually refers to either: an image or series of images ...

for the DEC SRC technical reports. In 1992 Jorge collected and widely disseminated (through the historic DEC gatekeeper ftp archives and Prime Time Freeware) a set of wordlists that later formed the basis of the

ispell Ispell is a spelling checker for Unix that supports most Western languages. It offers several interfaces, including a programmatic interface for use by editors such as Emacs. Unlike GNU Aspell, ispell will only suggest corrections that are based ...

resources (later

myspell MySpell is a spell checker that was formerly included with OOo Writer of the free OpenOffice.org office suite. Since version 2.0.2, OpenOffice.org has replaced MySpell with Hunspell. Background MySpell was started by Kevin Hendricks in an att ...

, currently part of

OpenOffice.org OpenOffice.org (OOo), commonly known as OpenOffice, is a discontinued open-source office suite. Active successor projects include LibreOffice (the most actively developed), Apache OpenOffice, Collabora Online (enterprise ready LibreOffice) a ...

and

Mozilla Mozilla (stylized as moz://a) is a free software community founded in 1998 by members of Netscape. The Mozilla community uses, develops, spreads and supports Mozilla products, thereby promoting exclusively free software and open standards, wi ...

hunspell Hunspell is a spell checker and morphological analyser designed for languages with rich morphology and complex word compounding and character encoding, originally designed for the Hungarian language. Hunspell is based on MySpell and is backwar ...

). After moving to UNICAMP, Jorge developed affine arithmetic, a model for self-validated computation (which he had conceived in 1991), in collaboration with Marcus Andrade, João Comba, and Luiz Figueiredo. At UNICAMP Jorge also worked with C. Lucchesi and T.Kowaltowski on

finite state transducer A finite-state transducer (FST) is a finite-state machine with two memory ''tapes'', following the terminology for Turing machines: an input tape and an output tape. This contrasts with an ordinary finite-state automaton, which has a single tape ...

technology for spell checking and other

natural language processing Natural language processing (NLP) is an interdisciplinary subfield of linguistics, computer science, and artificial intelligence concerned with the interactions between computers and human language, in particular how to program computers to pro ...

tasks. With his student H. Leitão he developed an efficient algorithm for pottery fragment reassembly by multiscale outline matching, and analyzed the density of useful information contained in those outlines. He has also contributed to the study of the

Voynich manuscript The Voynich manuscript is an illustrated codex hand-written in an otherwise unknown writing system, referred to as 'Voynichese'. The vellum on which it is written has been carbon-dated to the early 15th century (1404–1438), and stylistic anal ...

. Since 2001 Jorge has been involved in efforts to raise public and government awareness about the insecurity of Brazilian

electronic voting machine An electronic voting machine is a voting machine based on electronics. Two main technologies exist: '' optical scanning'' and '' direct recording'' (DRE). Optical scanning In an optical scan voting system, or marksense, each voter's choices ...

s, which are of the direct recording electronic (DRE) type and therefore vulnerable to massive and undetectable software-based vote-stealing.

Bitcoin skepticism

Starting late 2013, Jorge took an active interest in the economics of

cryptocurrencies A cryptocurrency, crypto-currency, or crypto is a digital currency designed to work as a medium of exchange through a computer network that is not reliant on any central authority, such as a government or bank A bank is a financial i ...

. He became skeptical about its underlying soundness and chances of success and has been advising the Brazilian public against investment in

bitcoin Bitcoin ( abbreviation: BTC; sign: ₿) is a decentralized digital currency that can be transferred on the peer-to-peer bitcoin network. Bitcoin transactions are verified by network nodes through cryptography and recorded in a public distr ...

.(2013
Cuidado com Bitcoin!
Blogpost (in Portuguese) at AdVivo.com, Accessed on 2014-04-12. In 2016 he submitted a letter to the SEC outlining what he perceives as similarities between Bitcoin and

penny stock Penny stocks are common shares of small public companies that trade for less than one dollar per share. The U.S. Securities and Exchange Commission (SEC) uses the term "Penny stock" to refer to a security, a financial instrument which represents a ...

s or

Ponzi scheme A Ponzi scheme (, ) is a form of fraud that lures investors and pays profits to earlier investors with funds from more recent investors. Named after Italian businessman Charles Ponzi, the scheme leads victims to believe that profits are comin ...

s.(2016

Letter to the SEC dated 2016-07-13 In response, another person by the name of Colin Baird wrote the SEC to cast doubt on Stolfi's letters, without addressing any of Stolfi's arguments.(2016

Rebuttal letter to the SEC dated 2016-11-28 In 2021, Stolfi wrote a paper titled "Bitcoin is a Ponzi", in which he summarized the main characteristics of a Ponzi scheme, and its similarities with Bitcoin. The paper went viral after it was posted on Hacker News, HackerNews, a website frequented by computer programmers, where it received over 500 upvotes. In 2022, after posting to

Twitter Twitter is an online social media and social networking service owned and operated by American company Twitter, Inc., on which users post and interact with 280-character-long messages known as "tweets". Registered users can post, like, and ...

that "blockchain technology is a fraud", he inspired 1500 experts to write a letter to US Congress about the risks of cryptocurrencies.

References

External links

Jorge Stolfi's personal webpage
{{DEFAULTSORT:Stolfi, Jorge Brazilian scientists Free software programmers Living people 1950 births State University of Campinas faculty