This journal article was declassified and approved for public release on March 9, 2014. It covers the "American Cryptology During the Korean War" and focuses on communications intelligence, or COMINT. Challenges facing American intelligence workers during this time included the lack of Korean or Chinese linguists, and Russian interference. From the conclusion: "From what we can now glimpse, the bottom line on SIGINT in the Korean war paralleled the overall American experience during that war. There were successes and there were failures, but the failures tended to overshadow the successes. The war ended in a draw, a highly discomfiting outcome for the American public, the generals and admirals who led the fight, and the men and women who fought it."
CIA Freedom of Information Act Electronic Reading Room: http://www.foia.cia.gov/
Studies In Intelligence, v.45, no.3