The BBC has uncovered evidence that Sudan's security services tried to undermine popular protests by rounding up students, torturing them until they admitted to violent intent, and spreading false confession videos on Facebook and state TV. But the plot backfired, and now the students can tell their story.
"You are dirty! You are slaves!"
Racist insults rained down on John and his friends as, he claims, the security services beat them with fists and sticks and stunned them with electric shocks.
BBC Arabic's investigations team has spoken to multiple sources who can attest to the torture that John and his fellow students from Darfur underwent, for hours at a time.
John believes they were being tested: which of them would confess to being part of a Darfuri rebel group and inciting violence in Sudan?
Since mid-December, anti-government protests have rocked Sudan nearly every day. During the demonstrations, the government cracked down hard. Human rights groups say that well over 60 people have been killed. Many more have been injured and hundreds arrested.
The crackdown did not deter the protesters however. On 11 April President Omar al-Bashir was ousted in a military coup after 30 years in power.
John, whose name has been changed for this article because of concerns for his safety, hadn't taken part in the protests when they began in December. But that didn't stop him being swept up in a raid on a student house in Sennar, a town on the Blue Nile south-east of Khartoum.
When the protests started escalating, the National Intelligence Security Service (NISS) created propaganda to pin the unrest on rebels from Darfur.
Darfur is a region in the west of Sudan which has been ravaged by conflict since 2003.