In two key public messages this week, US National Security Agency whistleblower Edward Snowden has outlined the case against mass surveillance and how it can be defeated through greater use of encryption.

Overnight, Snowden made a rare public appearance via videolink to the SXSW technology conference in Texas (pictured). Earlier this week, he gave written testimony, including answers to questions, to a European Union parliamentary inquiry into mass surveillance. His appearance at SXSW, via a series of proxies to hide his location within Russia (officials in US intelligence agencies have openly discussed wanting to kill him), had been opposed by a US congressman who demanded the appearance be stopped.