I just need this two questioned answered–US History Cold War

Two sensational spy trials increased the country’s suspicion of
communists. Alger Hiss , a government employee who had helped organize the
United Nations, was accused of being a spy. Hiss denied the charges but was
still sentenced to prison. The second trial involved Julius and Ethel
Rosenberg . They were accused of passing secret information about nuclear
science to Soviet agents. Although the trial was controversial, the couple
was executed in 1953.

Questions
1. What was Alger Hiss convicted for?
2. What was controversial about the Rosenberg case?