Manuel Blum (born 26 April 1938 in Caracas, Venezuela) is a computer scientist who received the Turing Award in 1995 "In recognition of his contributions to the foundations of computational complexity theory and its application to cryptography and program checking".
In the 60s he developed an axiomatic complexity theory which was independent of concrete machine models. The theory is based on Gödel numberings and the Blum axioms. Even though the theory is not based on any machine model it yields concrete results like the compression theorem, the gap theorem, the honesty theorem and the Blum speedup theorem.
Some of his other work includes a protocol for flipping a coin over a telephone, a linear time Selection algorithm, the Blum Blum Shub pseudorandom number generator, the Blum-Goldwasser cryptosystem, and more recently CAPTCHAs.
Among his PhD advisees are Leonard Adleman, Shafi Goldwasser, Russell Impagliazzo, Silvio Micali, Gary Miller, Moni Naor, Steven Rudich, Michael Sipser, Umesh Vazirani and Vijay Vazirani, Ronitt Rubinfeld, Luis von Ahn, Nicholas Hopper, and Ryan Williams.
See also 
Blum's home pages: