A young woman walks down a street in Tehran, her hair uncovered, her jeans ripped, a bit of midriff exposed to the hot Iranian sun. An unmarried couple walk hand in hand. A woman holds her head high when asked by Iran’s once-feared morality police to put a hijab on, and tells them: “Screw you!”

These acts of bold rebellion – described to me by several people in Tehran over the past month – would have been almost unthinkable to Iranians this time last year. But that was before the death in the morality police’s custody of 22-year-old Mahsa Amini, who had been accused of not wearing her hijab [veil] properly.

The mass protests that shook Iran after her death subsided after a few months in the face of a brutal crackdown, but the anger that fuelled them has not been extinguished. Women have just had to find new ways to defy the regime.

A Western diplomat in Tehran estimates that across the country, an average of about 20% of women are now breaking the laws of the Islamic Republic by going out on to the streets without the veil.

“Things have changed so much since last year,” a 20-year-old music student in Tehran, who we are calling Donya, tells me over an encrypted social media platform. She is one of the many women who now refuse to wear the veil in public. “I still can’t believe the things I now have the courage to do. We’ve become so much bolder and braver.

“Even though I feel scared to my bones whenever I walk past the morality police, I keep my head up and pretend I haven’t seen them,” she says. “I wear what I like now when I go out.” But she quickly adds that the stakes are high, and she is not reckless. “I wouldn’t wear shorts. And I always carry a headscarf in my bag in case things get serious.”

She tells me that she knows of women who have been raped in custody, and cites reports of a woman sentenced to wash corpses as punishment for not wearing the hijab. All the women I spoke to referenced the surveillance cameras that monitor the streets to catch and fine those who flout the dress code.

The Western diplomat estimates that the proportion of women refusing to publicly wear the hijab in the ritzier neighbourhoods of north Tehran is even higher than 20%. But he stresses that the rebellion is not limited to the capital.

“It’s a generational thing much more than a geographical thing… it’s not just your bright educated people, it’s basically any young person with a smartphone… so that’s what takes you right out into the villages, and all over.”

The diplomat describes the protests sparked by Mahsa Amini’s death as a huge, and terminal, “turning point” for the regime, which has tried to control how women dress and behave for more than four decades.

“It turned [the regime] into a one-way street with a dead-end,” he says. “The only thing we don’t know is how long the street is.”

The uprising, led by women, was the most serious challenge to Iran’s theocratic regime since the revolution of 1979. In crushing it, human rights groups say the regime killed more than 500 people. Thousands were wounded – some blinded after being shot in the face. At least 20,000 Iranians were arrested, with accounts of torture and rape in jail. And seven protesters were executed – one of them publicly hanged from a crane. As intended, this had a chilling effect.

In an apparent attempt to prevent further unrest to mark the anniversary of Mahsa Amini’s death, the authorities have carried out another wave of arrests. Among those locked up are women’s rights activists, journalists, singers, and relatives of people killed during the protests. Academics deemed unsupportive of the regime have also been purged from their jobs.

But extraordinary acts of quiet defiance continue every day.

Donya says people in Tehran continue to deface government billboards and to write “#Mahsa” and “Woman, Life, Freedom” – the rallying cry of the protests – on walls, mostly on the subway.

“The government keeps wiping them out but the slogans keep coming back.”

She, and the other women I spoke to, all stressed that this is not a struggle they are waging alone – with many men keen to support them.

“Some of them wear sleeveless clothes and shorts or wear make-up when they go on the streets, because these things are illegal for men to wear. Some men wear mandatory hijab on the streets to show how bizarre it looks when you force someone to wear something they do not like.”

The morality police patrols, which were temporarily paused in the wake of the protests following Mahsa Amini’s death, have been visible again in the past few weeks – though Donya says they seem to be wary of provoking direct confrontation for fear of reigniting mass demonstrations.

But the authorities have sought to impose control in other ways in the past year. They have shut down hundreds of businesses for serving unveiled women, and have been issuing fines and impounding cars driven by women not wearing the headscarf.

Currently women without the veil risk a 5,000-500,000 rial [$0.12-$11.83] fine or a prison spell of between 10 days and two months.

“Bahareh”, 32, says she’s already received three text warnings on her phone from the authorities, after being captured on CCTV driving in Tehran without the veil. She says if they catch her again they might impound her car.

According to the police in one province alone – East Azerbaijan province – 439 cars had been impounded as of 11 August for hijab infringements.

Bahareh has also been stopped from going into the city’s metro and into shopping centres. Hardest of all, she was prevented from attending celebrations at her son’s school to mark the end of his first year there.

But she is also clear in her mind that there is no going back, recalling the thrill she experienced when she first took off her headscarf in public last September.

“My heart was pounding. It was so exciting. I felt like I’d broken a huge taboo.”

Now she’s so used to it, she doesn’t even carry one with her.

“Not wearing it is the only tool I have to show my civil disobedience, not just against the hijab but against all the laws of the dictatorship, all the suffering that Iranians have endured over the past 43 years. I will keep going for all the mothers and fathers who have to wear black in mourning for their children.”

It’s impossible to gauge exactly how many people would like to see the end of the Islamic Republic, but fury at the regime is widespread, according to film-maker Mojgan Ilanlou, who was jailed last October for four months after taking off her veil and criticising Iran’s supreme leader. She was briefly detained again last month in an effort , she says, to intimidate her.

“The women of Iran have crossed the threshold of fear,” she tells me from her home in Tehran, though she admits that the latest round of repression has been so “horrifying” that for 10 days last month she decided to de-activate her Instagram account – where she regularly posts pictures of herself unveiled in public.

“This is a marathon not a sprint,” she says, likening it to the moment Rosa Parks refused to give up her seat to a white man on a bus, igniting the US civil rights movement. “Her refusal to give up her seat wasn’t just about a person sitting on a chair. It’s a statement telling others: ‘I’m not afraid of you. Look at me. I have power.’”

And Ilanlou says it’s working. Men’s attitudes towards women are changing, even in more conservative parts of the country, she says. A social revolution is under way.

“Society won’t go back to the pre-Mahsa time,” she believes. “In the streets, in the metro and in bazaars, men now admire women and praise their courage… Remarkably, even in some very religious cities like Qom, Mashhad and Isfahan, women no longer wear a headscarf.”

She, like the Tehran-based diplomat, insists this is a rebellion that cuts across social classes. She describes street vendors unveiled on the metro. And she told me that she’d shared a crammed lice-infested room in Qarchak jail last year with a young impoverished woman – who became a mother at just 11 years old – who had also refused to wear her headscarf.

And it’s not just the hijab. Ilanlou says women are now making other demands, such as for equal rights in a marriage contract.

For Elahe Tavokolian – a former factory manager – and others, the sacrifice has been heavy. She misses her children, 10-year old twins, desperately.

From the suburbs of Milan where she now lives, in borrowed spare rooms, she calls them whenever she can.

As she talks about them, tears roll down her cheek from her left eye.

Elahe, who had never taken part in protests before last September, was shot by Iranian security forces in Esfarayen in the north of the country.

“I was with the children and we’d just been buying supplies for the start of school. They were covered in my blood.”

Escaping to Turkey, she got a medical visa to travel to Italy, where surgeons removed her right eye and the bullet which had penetrated it.

She still needs another operation so that she can close the eyelid over her new glass eye.

And she has no idea when it will be safe for her to return to Esfarayen, and see her children again.

“Whenever we speak, we always talk of our hope that we can be together again in Iran, in better days.”

For now, those better days seem a long way away.

Human rights groups say no Iranian official has ever been held to account for Mahsa Amini’s death and the ensuing crackdown.

And the regime is not backing down – quite the reverse. A draft law currently before parliament – the so-called Hijab and Chastity Bill – would impose new punishments on women who go unveiled, including fines of 500m-1bn rials [$118-$23,667] and prison terms of up to 10 years for “those who do not comply… in an organised way or encourage others to do so”. It’s been described by UN-appointed human rights experts as a “form of gender apartheid”.

The government has “dug its heels in”, according to Jasmin Ramsey, deputy director of the New York-based NGO The Center for Human Rights in Iran.

But the Iranian population refuses to surrender, she says.

“Iran remains a tinderbox, ready to ignite at any moment.”

Additional research by Shayan Sardarizadeh, BBC Verify