Snowden could not attend the ceremony, but sent a message via a video, urging to fight for the observation of human rights.
"If we are to live in a liberal society, we must stand and defend liberal values," Snowden said.
The whistleblower added that it was important to defend human rights and demand that even the most senior officials observe them, as government and democracy should be founded on people's trust.
In 2013, Snowden leaked classified information from the National Security Agency (NSA), concerning electronic surveillance programs, conducted by US authorities around the world, which included eavesdropping on US citizens and foreign leaders.
Following the incident, the whistleblower was charged with espionage in the United States, with his passport being revoked. In August 2013, Snowden was granted temporary asylum in Russia for one year. The asylum period was extended by the Russian government for three more years in August 2014.