We all know now that Stalin's real name was Jughashvili (Ioseb Besarionis dzе Jughashvili). Lenin was actually Ulyanov, Trotsky was Lev Davidovich Bronstein, Kamenev was Leo Rosenfeld, etc.
Searching through literature and internet (both international and Russian) you could find many explanations as to why the Bolsheviks had pseudonyms, how Stalin chose to be Stalin and Koba before that, etc.
However, I could not find information on whether the average Soviet citizen (let's say a factory worker or kolkhoz farmer) knew or could have known the birth name of Stalin or other Soviet leaders, even those who were disgraced like Trotsky. Note that Soviet press and other media constantly praised Stalin and maligned Trotsky after his exile in 1929. But I could not find any information that they ever used the birth names of either of them. And if not the press, did at least Soviet encyclopedias (available to a much smaller circle of academics) mention these details? Were there even word-of-mouth rumors about the origins and birth names of the leaders?
EDIT : To clarify matters further, I will give one simple example. After the capture of Yakov Dzhugashvili, Germans issued propaganda leaflets calling him elder Stalin's son. Could average Soviet soldier (poor peasant or factory worker) make a connection between Dzhugashvili and Stalin, which is of course necessary for propaganda to work ?