For a time, Hong Kong had been off the international radar. But last month we were catapulted into world headlines by the sudden appearance of Edward Snowden - a former CIA employee and whistle-blower who has been denounced as a traitor by the US government but who proclaims himself a true American with rights to conscience. Snowden said Hong Kong and the mainland were targets of CIA cybersurveillance. He chose Hong Kong to make his revelation because of our city's reputation for freedom of speech and governance by the rule of law. Instantly, he became the flavour of the month. He even appeared to have united Hong Kong legislators across the political divide. Yet as suddenly as he came, he left Hong Kong, having sown the seeds of suspicion and Orwellian fear everywhere. Doubt and distrust tend to fester and feed on each other. They are likely to derail any collaborative effort on cybersecurity, discussed between US president Barack Obama and Chinese president Xi Jinping at their historical meeting at the Sunnylands estate last month. They also encourage the construction of firewalls in cyberspace by those who want to protect their interests. How well do we remember the Berlin Wall which separated East and West Germany during the cold war? Walls divide and subjugate rather than unite and liberate. The dangers of a new war - the Code War - loom large on the internet horizon. Cybersecurity is by far the single greatest economic, educational, social, political, legal and international challenge we face today. Unless an international code to govern acceptable behaviour of internet users is discussed, devised, understood and accepted for implementation, a digital equivalent of the Berlin Wall might well become the centre of the Code War. Under "one country two systems", we in Hong Kong are well placed to help avoid any such war from developing. With our legacy of the rule of law and freedom of speech, our bi-cultural understanding of the East and the West, and our many experts in law and information technology, what better place is there than Hong Kong to initiate discussion and to act as a buffer in this field in collaboration with the two giants and the rest of the world? Impossible? All things seem impossible until they are proven otherwise. Who would have imagined Nelson Mandela, incarcerated for decades in South African prisons, would in 1994 become the President of South Africa? Who would have thought, as he left the prison walls, he also left bitterness and hatred behind? Let's not waste a golden opportunity for Hong Kong to take the lead and make a difference to the world. Elizabeth Wong Chien Chi-lien was secretary for health and welfare from 1990 to 1994 and a legislative councillor from 1995 to 1997