Proceedings of the National Academy of Sciences of the United States of America

About the PNAS Member Editor
Name Blum, Manuel
Location Carnegie Mellon University
Primary Field Computer and Information Sciences
Secondary Field Mathematics
 Election Citation
Blum is a computer and information scientist who has made seminal contributions to computational complexity theory and its applications to cryptography and program checking. He showed that secure business transactions and pseudo-random number generation are possible because of the finite resources of computational devices. Blum's theoretical breakthroughs have had many practical applications: as just one example, his "completely automated public Turing test" ensures that registrants to Web sites are humans and not robots.
 Research Interests
I am interested in theoretical computer science, including complexity theory, algorithms, machine learning, and cryptographic protocols. My interest in computer science arose out of my interest in brains and my desire to understand "thinking." Toward this end I worked for several years in the Neurophysiology Laboratory of Warren S. McCulloch and Walter Pitts and did my Ph.D. work under artificial intelligence maestro Marvin Minsky. I am designing an intelligent, conscious robot as part of my CAPTCHA project - Completely Automatic Public Turing Test to Tell Computers and Humans Apart. CAPTCHA programs seek to distinguish humans from computers and generate and grade tests that humans can easily pass but computers will fail. This is a paradoxical requirement, as this means that a CAPTCHA must be able to grade a test that it cannot itself pass. Can there even exist a test that humans can pass but that a computer cannot? I believe there will come a time when computers can pass all tests that any human can pass, and I hope to share in the creation of such computer. Until then, CAPTCHAs can and do exist (see ).

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