Venona project The Venona project was a counter - intelligence program initiated by the United States Army Signal Intelligence Service ( a forerunner of the National Security Agency ) that lasted from 1943 to 1980 . The program attempted to decrypt messages sent by Soviet Union intelligence agencies , including its foreign intelligence service and military intelligence services . During the program ' s four decades , approximately 3 , 000 messages were at least partially decrypted and translated . The project produced some of the most important breakthroughs for western counter - intelligence in this period , including the discovery of the Cambridge spy ring and the exposure of Soviet espionage targeting the Manhattan Project . The project was one of the most sensitive secrets of United States intelligence . It remained secret for over a decade after it ended and was not officially declassified until 1995 . Background . During the initial years of the Cold War , the Venona project was a source of information on Soviet intelligence - gathering activity that was directed at the Western military powers . Although unknown to the public , and even to Presidents Franklin D . Roosevelt and Harry S . Truman , these programs were of importance concerning crucial events of the early Cold War . These included the Julius and Ethel Rosenberg spying case and the defections of Donald Maclean and Guy Burgess to the Soviet Union . Most decipherable messages were transmitted and intercepted between 1942 and 1945 . Sometime in 1945 , the existence of the Venona program was revealed to the Soviet Union by the NKVD agent and United States Army SIGINT analyst and cryptologist Bill Weisband . These messages were slowly and gradually decrypted beginning in 1946 and continuing ( many times at a low - level of effort in the latter years ) through 1980 , when the Venona program was terminated , and the remaining amount of effort that was being spent on it was moved to more important projects . To what extent the various individuals were involved with Soviet intelligence is a topic of dispute . While a number of academics and historians assert that most of the individuals mentioned in the Venona decrypts were most likely either clandestine assets and / or contacts of Soviet intelligence agents , others argue that many of those people probably had no malicious intentions and committed no crimes . Commencement . The Venona Project was initiated in 1943 , under orders from the deputy Chief of Military Intelligence ( G - 2 ) , Carter W . Clarke . Clarke distrusted Joseph Stalin , and feared that the Soviet Union would sign a separate peace with the Third Reich , allowing Germany to focus its military forces against Great Britain and the United States . Code - breakers of the US Army ' s Signal Intelligence Service ( commonly called Arlington Hall ) analyzed encrypted high - level Soviet diplomatic intelligence messages intercepted in large volumes during and immediately after World War II by American , British , and Australian listening posts . Decryption . This message traffic , which was encrypted with a one - time pad system , was stored and analyzed in relative secrecy by hundreds of cryptanalysts over a 40 - year period starting in the early 1940s . Due to a serious blunder on the part of the Soviets , some of this traffic was vulnerable to cryptanalysis . Somebody who was working for the manufacturers of Soviet secret - communication materials had reused pages of some of the one - time pads in other pads , which were then used for other secret messages . This defeated the purpose of the one - time pad , which provides perfect security when each page is used exactly once and then disposed of . It is unclear as to why this mistake was made , or by whom . Breakthrough . The Soviet systems in general used a code to convert words and letters into numbers , to which additive key s ( from one - time pad s ) were added , encrypting the content . When used correctly , one - time pad encryption is unbreakable . Cryptanalysis by American and British code - breakers revealed that some of the one - time pad material had incorrectly been reused by the Soviets ( specifically , entire pages , although not complete books ) , which allowed decryption ( sometimes only partial ) of a small part of the traffic . Generating the one - time pads was a slow and labor - intensive process , and the outbreak of war with Germany in June 1941 caused a sudden increase in the need for coded messages . It is probable that the Soviet code generators started duplicating cipher pages in order to keep up with demand . It was Arlington Hall ' s Lieutenant Richard Hallock , working on Soviet " Trade " traffic ( so called because these messages dealt with Soviet trade issues ) , who first discovered that the Soviets were reusing pages . Hallock and his colleagues ( including Genevieve Feinstein , Cecil Phillips , Frank Lewis , Frank Wanat , and Lucille Campbell ) went on to break into a significant amount of Trade traffic , recovering many one - time pad additive key tables in the process . A young Meredith Gardner then used this material to break into what turned out to be NKVD ( and later GRU ) traffic by reconstructing the code used to convert text to numbers . Samuel Chew and Cecil Phillips also made valuable contributions . On 20 December 1946 , Gardner made the first break into the code , revealing the existence of Soviet espionage in the Manhattan Project . Venona messages also indicated that Soviet spies worked in Washington in the State Department , Treasury , Office of Strategic Services , and even the White House . Very slowly , using assorted techniques ranging from traffic analysis to defector information , more of the messages were decrypted . Claims have been made that information from the physical recovery of code books ( a partially burned one was obtained by the Finns ) to bugging embassy rooms in which text was entered into encrypting devices ( analyzing the keystrokes by listening to them being punched in ) contributed to recovering much of the plaintext . These latter claims are less than fully supported in the open literature . One significant aid ( mentioned by the NSA ) in the early stages may have been work done in cooperation between the Japan ese and Finnish cryptanalysis organizations ; when the Americans broke into Japanese codes during World War II , they gained access to this information . There are also reports that copies of signals purloined from Soviet offices by the Federal Bureau of Investigation ( FBI ) were helpful in the cryptanalysis . The Finnish radio intelligence sold much of its material concerning Soviet codes to OSS in 1944 during Operation Stella Polaris , including the partially burned code book . Results . NSA reported , according to the serial numbers of the Venona cables , thousands were sent , but only a fraction were available to the cryptanalysts . Approximately 2 , 200 messages were decrypted and translated ; about half for the 1943 GRU - Naval Washington to Moscow messages were broken , but none for any other year , although several thousand were sent between 1941 and 1945 . The decryption rate of the NKVD cables was as follows : Out of some hundreds of thousands of intercepted encrypted texts , it is claimed under 3 , 000 have been partially or wholly decrypted . All the duplicate one - time pad pages were produced in 1942 , and almost all of them had been used by the end of 1945 , with a few being used as late as 1948 . After this , Soviet message traffic reverted to being completely unreadable . The existence of Venona decryption became known to the Soviets within a few years of the first breaks . It is not clear whether the Soviets knew how much of the message traffic or which messages had been successfully decrypted . At least one Soviet penetration agent , British Secret Intelligence Service representative to the U . S . , Kim Philby , was told about the project in 1949 , as part of his job as liaison between British and U . S . intelligence . Since all of the duplicate one - time pad pages had been used by this time , the Soviets apparently did not make any changes to their cryptographic procedures after they learned of Venona . However , this information allowed them to alert those of their agents who might be at risk of exposure due to the decryption . Significance . The decrypted messages gave important insights into Soviet behavior in the period during which duplicate one - time pads were used . With the first break into the code , Venona revealed the existence of Soviet espionage at Los Alamos National Laboratories . Identities soon emerged of American , Canadian , Australian , and British spies in service to the Soviet government , including Klaus Fuchs , Alan Nunn May , and Donald Maclean . Others worked in Washington in the State Department , the Treasury , Office of Strategic Services , and even the White House . The decrypts show the U . S . and other nations were targeted in major espionage campaigns by the Soviet Union as early as 1942 . Among those identified are Julius and Ethel Rosenberg ; Alger Hiss ; Harry Dexter White , the second - highest official in the Treasury Department ; Lauchlin Currie , a personal aide to Franklin Roosevelt ; and Maurice Halperin , a section head in the Office of Strategic Services . The identification of individuals mentioned in Venona transcripts is sometimes problematic , since people with a " covert relationship " with Soviet intelligence are referenced by cryptonyms . Further complicating matters is the fact the same person sometimes had different cryptonyms at different times , and the same cryptonym was sometimes reused for different individuals . In some cases , notably Hiss , the matching of a Venona cryptonym to an individual is disputed . In many other cases , a Venona cryptonym has not yet been linked to any person . According to authors John Earl Haynes and Harvey Klehr , the Venona transcripts identify approximately 349 Americans whom they claim had a covert relationship with Soviet intelligence , though fewer than half of these have been matched to real - name identities . However , not every agent may have been communicating directly with Soviet intelligence . Each of those 349 persons may have had many others working for , and reporting only to , them . The Office of Strategic Services , the predecessor to the CIA , housed at one time or another between fifteen and twenty Soviet spies . Duncan Lee , Donald Wheeler , Jane Foster Zlatowski , and Maurice Halperin passed information to Moscow . The War Production Board , the Board of Economic Warfare , the Office of the Coordinator of Inter - American Affairs and the Office of War Information , included at least half a dozen Soviet sources each among their employees . In the opinion of some , almost every American military and diplomatic agency of any importance was compromised to some extent by Soviet espionage . Some scholars and journalists dispute the claims by Haynes , Klehr , and others concerning the precision of the matching of cryptonyms to actual persons . Also contested is the implication that all 349 persons identified had an intentional " covert relationship " with Soviet intelligence ; it is argued , in some cases , the individual may have been an unwitting information source or a prospect for future recruitment by Soviet intelligence . Bearing of Venona on particular cases . Venona has added information — some unequivocal , some ambiguous — to several espionage cases . Some known spies , including Theodore Hall , were neither prosecuted nor publicly implicated , because the Venona evidence against them was not made public . The identity of Soviet source cryptonymed ' 19 ' remains unclear . According to British writer Nigel West , ' 19 ' was president of Czechoslovak government - in - exile Edvard Beneš . Military historian Eduard Mark and American authors Herbert Romerstein and Eric Breindel concluded it was Roosevelt ' s aide Harry Hopkins . According to American authors John Earl Haynes and Harvey Klehr , source code - named ' 19 ' could be someone from the British delegation to the Washington Conference in May 1943 . Moreover , they argue no evidence of Hopkins as an agent has been found in other archives , and the partial message relating to " 19 " does not indicate if this source was a spy . However , Vasily Mitrokhin was a KGB archivist who defected from the Soviet Union with copies of KGB files . He claimed Harry Hopkins was a secret Russian agent . Moreover , Oleg Gordievsky , a high - level KGB officer who also defected from the Soviet Union , reported that Iskhak Ahkmerov , the KGB officer who controlled the clandestine Soviet agents in the U . S . during the war , had said Hopkins was “ the most important of all Soviet wartime agents in the United States . ” In addition , Major George Racey Jordon stated he strongly suspected Hopkins was a spy based on activities he observed in his support role in the project known as " Lend - Lease . " Julius and Ethel Rosenberg . Venona has added significant information to the case of Julius and Ethel Rosenberg , making it clear Julius was guilty of espionage , but also showing that Ethel was probably no more than an accomplice , if that . Venona and other recent information has shown , while the content of Julius ' atomic espionage was not as vital as alleged at the time of his espionage activities , in other fields it was extensive . The information Rosenberg passed to the Soviets concerned the proximity fuze , design and production information on the Lockheed P - 80 jet fighter , and thousands of classified reports from Emerson Radio . The Venona evidence indicates unidentified sources code - named " Quantum " and " Pers " who facilitated transfer of nuclear weapons technology to the Soviet Union from positions within the Manhattan Project . Alger Hiss and Harry Dexter White . According to the Moynihan Commission on Government Secrecy , the complicity of both Alger Hiss and Harry Dexter White is conclusively proven by Venona , stating " The complicity of Alger Hiss of the State Department seems settled . As does that of Harry Dexter White of the Treasury Department . " In his 1998 book , Senator Moynihan expresses certainty about Hiss ' s identification by Venona as a Soviet spy , writing " Hiss was indeed a Soviet agent and appears to have been regarded by Moscow as its most important . " Several current authors , researchers , and archivists consider the Venona evidence on Hiss to be inconclusive or incorrect . Donald Maclean and Guy Burgess . When Kim Philby learned of Venona in 1949 , he obtained advance warning that his fellow Soviet spy Donald Maclean was in danger of being exposed . The FBI told Philby about an agent cryptonymed ' Homer ' , whose 1945 message to Moscow had been decoded . As it had been sent from New York and had its origins in the British Embassy in Washington , Philby , who would not have known Maclean ' s cryptonym , deduced the sender ' s identity . By early 1951 , Philby knew U . S . intelligence would soon also conclude Maclean was the sender , and advised Moscow to recall Maclean . This led to Maclean and Guy Burgess ' flight to Russia in May 1951 . Soviet espionage in Australia . In addition to British and Americans , Australians collected Venona intercepts at a remote base in the Outback . The Soviets remained unaware of this base as late as 1950 . The founding of the Australian Security Intelligence Organisation by Labor Prime Minister Ben Chifley was considered highly controversial within Chifley ' s own party . Until then , the left - leaning Australian Labor Party had been hostile to domestic intelligence agencies on civil liberties grounds and a Labor government founding one was a surprising about face . It was the revelation of Venona material to Chifley revealing evidence of Soviet agents operating in Australia that brought this about . As well as Australian diplomat suspects abroad , Venona had revealed Wally Clayton ( cryptonym ' KLOD ' ) , a leading official within the Communist Party of Australia , was the chief organiser of Soviet intelligence gathering in Australia . Investigation revealed he formed an underground network within the CPA so the party could continue to operate if it were banned . Public disclosure . For much of its history , knowledge of Venona was restricted even from the highest levels of government . Senior army officers , in consultation with the FBI and CIA , made the decision to restrict knowledge of Venona within the government ( even the CIA was not made an active partner until 1952 ) . Army Chief of Staff Omar Bradley , concerned about the White House ' s history of leaking sensitive information , decided to deny President Truman direct knowledge of the project . The president received the substance of the material only through FBI , Justice Department , and CIA reports on counterintelligence and intelligence matters . He was not told the material came from decoded Soviet ciphers . To some degree this secrecy was counter - productive ; Truman was distrustful of FBI head J . Edgar Hoover and suspected the reports were exaggerated for political purposes . Some of the earliest detailed public knowledge that Soviet code messages from World War II had been broken came with the release of Robert Lamphere ' s book , " The FBI - KGB War " , in 1986 . Lamphere had been the FBI liaison to the code - breaking activity , had considerable knowledge of Venona and the counter - intelligence work that resulted from it . MI5 assistant director Peter Wright ' s 1987 memoir , " Spycatcher " , however , was the first detailed account of the Venona project , identifying it by name and making clear its long - term implications in post - war espionage . Many inside the NSA had argued internally that the time had come to publicly release the details of the Venona project , but it was not until 1995 that the bipartisan Commission on Government Secrecy , with Senator Moynihan as chairman , released Venona project materials . Moynihan wrote : " [ The ] secrecy system has systematically denied American historians access to the records of American history . Of late we find ourselves relying on archives of the former Soviet Union in Moscow to resolve questions of what was going on in Washington at mid - century . [ . . . ] the Venona intercepts contained overwhelming proof of the activities of Soviet spy networks in America , complete with names , dates , places , and deeds . " One of the considerations in releasing Venona translations was the privacy interests of the individuals mentioned , referenced , or identified in the translations . Some names were not released because to do so would constitute an invasion of privacy . However , in at least one case , independent researchers identified one of the subjects whose name had been obscured by the NSA . The dearth of reliable information available to the public — or even to the President and Congress — may have helped to polarize debates of the 1950s over the extent and danger of Soviet espionage in the United States . Anti - Communists suspected many spies remained at large , perhaps including some known to the government . Those who criticized the governmental and non - governmental efforts to root out and expose communists felt these efforts were an overreaction ( in addition to other reservations about McCarthyism ) . Public access — or broader governmental access — to the Venona evidence would certainly have affected this debate , as it is affecting the retrospective debate among historians and others now . As the Moynihan Commission wrote in its final report : " A balanced history of this period is now beginning to appear ; the Venona messages will surely supply a great cache of facts to bring the matter to some closure . But at the time , the American Government , much less the American public , was confronted with possibilities and charges , at once baffling and terrifying . " The National Cryptologic Museum features an exhibit on the Venona project in its " Cold War / Information Age " gallery . Texas textbook controversy . Controversy arose in 2009 over the Texas State Board of Education ' s revision of their high school history class " curricula " to suggest Venona shows Senator Joseph McCarthy to have been justified in his zeal in exposing those whom he believed to be Soviet spies or communist sympathizers . Critics assert most people and organizations identified by McCarthy were not mentioned in the Venona content , and sources for his accusations remain largely unknown . Critical views . A number of writers and scholars have taken a critical view of the translations released by the NSA . A few critics , including Robert and Michael Meeropol , the sons of Ethel and Julius Rosenberg , and activist lawyer William Kunstler , cast doubt on the authenticity of the Venona material , suggesting that it might have been at least in part forged . Other critics have questioned the accuracy of the translations and the identifications of covernames that the NSA translations give . Writers Walter and Miriam Schneir , in a lengthy 1999 review of one of the first book - length studies of the messages , object to what they see as the book ’ s overconfidence in the translations ’ accuracy , noting that the undecrypted gaps in the texts can make interpretation difficult , and emphasizing the problem of identifying the individuals mentioned under covernames . To support their critique , they cite a declassified memorandum , written in 1956 by A . H . Belmont , who was assistant to FBI director J . Edgar Hoover at the time . In the memo , Belmont discusses the possibility of using the VENONA translations in court to prosecute Soviet agents , and comes out strongly opposed to their use . His reasons include legal uncertainties about the admissibility of the translations as evidence , and the difficulties that prosecution would face in supporting the validity of the translations . Belmont highlights the uncertainties in the translation process , noting that the cryptographers have indicated that “ almost anything included in a translation of one of these deciphered messages may in the future be radically revised . ” He also notes the complexities of identifying people with covernames , describing how the personal details mentioned for covername “ Antenna ” fit more than one person , and the investigative process required to finally connect “ Antenna ” to Julius Rosenberg . The Schneirs conclude that " A reader faced with Venona ' s incomplete , disjointed messages can easily arrive at a badly skewed impression . " Many of the critiques of the Venona translations have been based on specific cases . The Schneirs ' critique of the Venona documents was based on their decades of work on the case of Ethel and Julius Rosenberg . Another critique of the Venona translations came from the late Rutgers University law professor John Lowenthal , who as a law student worked as a volunteer for Alger Hiss ' s defense team , and later wrote extensively on the Hiss case . Lowenthal ' s critique focused on one message ( Venona 1822 KGB Washington - Moscow 30 March 1945 ) , in which the comments identified the covername ' Ales ' as " probably Alger Hiss . " Lowenthal raised a number of objections to this identification , rejecting it as " a conclusion psychologically motivated and politically correct but factually wrong . " Lowenthal ' s article led to an extended debates on the ' Ales ' message , and even prompted the NSA to declassify the original Russian text . Currently Venona 1822 is the only message for which the complete decrypted Russian text has been published . Victor Navasky , editor and publisher of " The Nation " , has also written several editorials highly critical of John Earl Haynes ' and Harvey Klehr ' s interpretation of recent work on the subject of Soviet espionage . Navasky claims the Venona material is being used to “ distort … our understanding of the cold war ” and that the files are potential “ time bombs of misinformation . ” Commenting on the list of 349 Americans identified by Venona , published in an appendix to " Venona : Decoding Soviet Espionage in America " , Navasky wrote , " The reader is left with the implication — unfair and unproven — that every name on the list was involved in espionage , and as a result , otherwise careful historians and mainstream journalists now routinely refer to Venona as proof that many hundreds of Americans were part of the red spy network . " Navasky goes further in his defense of the listed people and has claimed a great deal of the so - called espionage that went on was nothing more than “ exchanges of information among people of good will ” and that “ most of these exchanges were innocent and were within the law . ” According to historian Ellen Schrecker , " Because they offer insights into the world of the secret police on both sides of the Iron Curtain , it is tempting to treat the FBI and Venona materials less critically than documents from more accessible sources . But there are too many gaps in the record to use these materials with complete confidence . " Schrecker believes the documents established the guilt of many prominent figures , but is still critical of the views of scholars such as John Earl Haynes , arguing , " complexity , nuance , and a willingness to see the world in other than black and white seem alien to Haynes ' view of history . " Despite the objections raised , however , many historians remain convinced of the historical value of the Venona material . Intelligence historian Nigel West believes that " Venona remain [ s ] an irrefutable resource , far more reliable than the mercurial recollections of KGB defectors and the dubious conclusions drawn by paranoid analysts mesmerized by Machiavellian plots . "