Mr. Proto was born and raised in New Haven, Conn., where he graduated in 1958 from Wilbur Cross High School.
He earned a bachelor's degree in mathematics from Fairfield University in 1962 and a master's in the discipline from Boston College in 1964.
Mr. Proto went to work at the NSA at Fort Meade in 1964, where he was a mathematician and chief of research before retiring in 1999.
"His ability to think strategically across a wealth of disciplines earned him a reputation as a strong leader and mentor, and earned him numerous high awards within and beyond the agency," said a daughter, Elissa J. Proto Carter of Catonsville.
Mr. Proto's awards included the Exceptional Civilian Service Award, the National Intelligence Medal of Honor and the Presidential Rank Award.
Until he was diagnosed with lung cancer in 2007, Mr. Proto continued consulting on intelligence matters with the U.S. Department of Defense and the intelligence community, his daughter said.
Mr. Proto was a self-taught guitarist who enjoyed playing folk music.
"He also enjoyed good food and intense political debates," Mrs. Carter said.
The former Laurel resident, who later moved to Columbia, also maintained a second home with his partner of 18 years, Ellen H. Rabe, in Mercersburg, Pa., where the couple enjoyed walking in the mountains.
A Mass of Christian burial will be offered at 10 a.m. today at Meadowridge Memorial Park, 7250 Washington Blvd., Elkridge.
Also surviving are a son, Christopher M. Proto of Washington; another daughter, Vanessa M. Proto of Baltimore; a brother, Neil Proto of Washington; and a sister, Diana Avino of Clinton, Conn. A marriage to the former Jeanne Rosner ended in divorce.