Hanna's deception in regards to her illiteracy--which is the main deception that she fronted--reveals society's lack of tolerance and acceptance of lesser educated people. To not be able to read in a society where books, education, and access to learning is so available, free, and normal, is an odd thing indeed. In Germany at this time, Hanna probably felt how many Germans valued education and intelligence as one of the most telling indicators of success and normal living. It was just assumed that one knew how to read, and if one didn't, one was judged as an idiot, a rural bumpkin who was ignorant and not worth spending time with. The illiterate were a lower class of people that others snubbed and looked down upon. For this reason, Hanna, living in the city where most people judged and ridiculed ignorance, kept her illiteracy a secret. Her shame revealed just how prejudiced and judgmental people were towards the "lower class uneducated."
Michael's deception in regards to not admitting he knew Hanna DURING their affair reveals that he understood a society that did not accept young boys having an affair with an older woman. That is pretty typical in most societies; he was afraid that if someone found out, they would end the affair and possibly get Hanna in trouble. So, their society was intolerant of the nature of their relationship. It also revealed a microcosm of society where the children felt alienated and disconnected from their parents; Michael was not comfortable telling his parents anything, and that was probably pretty common. His deception during and after the trial in regards to not admitting that he knew Hanna reflected Germany's post-war guilt that was associated with knowing what the Nazis had done, and feeling ashamed about it. Many Germans turned a blind eye to the Nazi's extermination of the Jews, and once all of the horrors were revealed, were ashamed not only of their country, but of themselves. Michael realized at that point just how involved Hanna had become, and his rejection of her is a symbol for how many Germans rejected and were ashamed of their own blindness in regards to the atrocities that were committed. Michael's deception revealed an entire attitude of shame, rejection, and confusion that was associated with thousands of Germans after WWII.
I hope that those thoughts help; good luck!