Just what is the truth?

Put aside the appearance of American journalist Glenn Greenwald at the Internet Party's - or more accurately Kim Dotcom's - Moment of Truth in Auckland on Monday night.

Put to one side the fact Mr Greenwald - whether he intended to or not - allowed himself to get mixed up in a partisan political event.

It prompted Prime Minister John Key to attack him for politicising the election and accuse him of being a henchman of Mr Dotcom.

It is a similar political attack Mr Key mounted against New Zealand investigative journalist Nicky Hager at the beginning of the campaign when Mr Hager published his book Dirty Politics. The book was dismissed by Mr Key as part of a left-wing conspiracy as he criticised Mr Hager's role.

It has been a consistent theme for the Prime Minister to respond to reportage critical of his government and his leadership with personal attacks.

Mr Greenwald opened himself up to those attacks through his association with internet businessman Mr Dotcom - a polarising figure in New Zealand.

But what is important here is the issue that Mr Greenwald's reportage and the testimony of American whistleblower Edward Snowden have uncovered.

Both men say New Zealand's electronic spy agency, the Government Communications Security Bureau (GCSB), has been involved in mass surveillance of this country's citizens. It is a charge Mr Key has rejected in the past and has done so again.

According to documents Mr Greenwald obtained from Mr Snowden, the GCSB had been involved in a project called Speargun to collect data on New Zealanders' electronic communications. The documents from the United States' National Security Agency reveal phase one of the programme had been completed and phase two was waiting for the new GCSB law to come into effect.

Mr Key responded by saying Mr Greenwald's information was outdated. He declassified Cabinet documents to reveal that the Government had planned to introduce a mass cyber protection scheme, which he confirms was called Speargun.

Mr Key says that programme never proceeded, though, and that the GCSB simply does not have the capacity to conduct mass surveillance of New Zealanders.

The CORTEX programme

Instead, a more limited project called CORTEX was approved by the Cabinet this year. Mr Key says it falls well short of the mass surveillance Glenn Greenwald and Edward Snowden allege is taking place.

Under the programme, government agencies and key businesses agree to have their systems monitored by the GCSB to protect against cyber attacks.

The businesses are not listed, but are likely to include the country's largest companies such as Fonterra, electricity companies, banks and information technology and telecommunications companies.

From the description of the project in Cabinet papers released by Mr Key, all communications with those organisations could be monitored by the GCSB. So potentially, every time someone checks their bank account online or goes to pay their electricity bill the GCSB could be watching.

A Cabinet paper this year says the CORTEX proposal is consistent with the amended GCSB Act and will in all cases operate with the consent of the participating organisations. It says technology can be used to separate personal communications from other data.

"The controls in question - which joint ministers have considered when reviewing the CORTEX proposal - will be specified in relevant warrants and access authorisations. They will include attention to how data is accessed, stored, sharing and disposed of. There will be no 'mass surveillance', and data will be accessed by GCSB only with the consent of owners of relevant networks or systems," the paper says.

But it is still not clear how the system would be able to recognise other data as a potential threat, and therefore worth monitoring, while recognising personal data as a non-threatening and protected by privacy concerns.

Individuals dealing with these organisations covered by CORTEX will not be approached to ask whether they are happy to have their communications caught up in this programme. This might not be mass surveillance, but it amounts to a level of monitoring which might surprise most people.

Era of 'mass surveillance'

Edward Snowden says mass surveillance is already underway using the NSA's tool XKEYSCORE. He says while working as a NSA contractor in Hawaii he was able to read New Zealanders' emails, as well as look at other electronic communications.

Mr Key does not dispute that but says it would only involve New Zealanders who had been identified as potential threats and for which warrants had been obtained to monitor their communications.

But he refuses to talk about XKEYSCORE, saying no government leader will talk about the systems its spy agencies use to collect information. So he expects the New Zealand public to trust the GCSB and the Government are doing the right thing.

Other governments in the intelligence sharing alliance Five Eyes - which includes the United States, Canada, Britain, Australia and New Zealand - have made the same case when confronted by the disclosures made by Edward Snowden.

While the information reported by Mr Greenwald and backed up by Mr Snowden this week is not conclusive, it does raise serious questions about the role of the GCSB. And it has forced Mr Key to make disclosures about the operations of the GCSB which have until now been secret.

But the information is also complex and difficult to understand. Computer nerds might get it - but many will not. As well, past concerns about the conduct of the electronic spy agency have not appeared to worry most New Zealanders.

They have been satisfied with Mr Key's defence of the spy agency, his assurance there has been no mass surveillance and his message that people who are not doing anything wrong have nothing to fear.

There is no suggestion - not yet anyway - that this week's Moment of Truth will do anything to sway public opinion.