J. Kenneth Conover, 70, who retired in 1965 as a cryptanalyst with the National Security Agency, died March 17 at the Veterans Administration Hospital in Martinsburg, W.Va., after a stroke.

Mr. Conover was a native of Atlantic City, N.J., and enlisted in the Navy in 1962. According to an NSA publication, he began his career in crytography while a Navy radioman. He solved a crytogram in the Navy Times in record time and was ordered to the Navy's cryptography course.

He was a cryptanalyst with Navy Communications in Washington before retiring from active duty with the rank of lieutenant in 1946. He stayed on with the Navy as a civilian cryptanalyst until joining the Armed Forces Security Agency in 1950. Three years later he became a supervisory cryptanalyst with the NSA.

Mr. Conover was head of the mathematics research division in the NSA's Office of Research for four years before retiring.

His numerous medals and commendations included the National Security Agency Meritorious Civilian Service Award in 1964. He also had received commendations and letters of appreciation signed by President Franklin D. Roosevelt and the then-secretary of the Navy, James Forrestal. One of these cited his "untiring efforts in supplying pertinent information" and credited him with "saving countless American lives during World War II."

Mr. Conover had made his home in the Washington area since 1940 and lived in Annandale since 1952.

Survivors include his wife, Lila E., of Annandale; two sons, William E., of Glen Burnie, and Paul J., of Fulton, N.Y.; one sister, Marie Jones of Columbus, Ohio, and five grandchildren.