...majority of work undertaken by the GDS, as most of the information that the department handles is rated as impact level 0, the lowest security rating.
On the occasions when the department has to handle more sensitive information, rated as restricted, civil servants use a separate, more secure system he said.
"Is it convenient? No it's not, but that's a very small part of what we do and the trade off is massive convenience in the system that they use every day and also a dramatic reduction in costs," he said.
Realising that much of the information that government handles is low risk, and treating it as such, will be vital if government is to transition its systems to the cloud, Chant said, who added that CESG is reviewing data security levels in government.
"The vast majority of what government does is open anyway. We've got to be realistic about what the security risks are. It opens up a lot of possibilities."
And the possibilities for cloud services go beyond just saving money, according to Chant, ranging from easier to use software that is accessible from anywhere over the net to keeping track of how much government is spending on IT thanks to a pay-as-you-go cloud service model.
When will the move to the cloud happen?
Public sector's shift to the cloud is expected to begin in earnest in January next year, when government bodies will be able to buy SaaS, IaaS, PaaS and cloud support services through a prototype version of the app store.
The clearest guide to the pace at which the public sector will shift to cloud computing is provided by the strategic implementation plan for its IT strategy.
The two major cloud deadlines in that strategy were for 50 accredited cloud products and services to be available through the government app store by the end of 2012, and for half of all new government IT spending to be on cloud services by the end of 2015.
To date, large scale deployments of cloud services within the public sector have been limited to a number of public bodies that are acting as test beds for the government's wider cloud rollout. These early adopters include authorities of varying sizes implementing differing cloud services - ranging from Warwickshire County Council rolling out Google Apps to 4,000 staff to the Home Office, which is deploying a private cloud platform with supplier Savvis.
As government prepares to launch its prototype app store Chant is the first to admit that this is virgin territory for the government and that mistakes will be made, and learned from.
"Getting these policies and processes right is a question of iteration, and we won't get that right on the first framework," he said.
But Chant is confident that - despite the challenges of overcoming government's longstanding love affair with big bang, bespoke technology - that the G-Cloud programme will be carried by the support within government. The project has backing from Cabinet Office minister Francis Maude downwards and the Cabinet Office's Major Project Authority and CIO Delivery Board will enforce a "public cloud first" directive when the public sector buys IT.
"This is about a concerted effort to get this right at all levels, the cloud strategy and strategic implementation plan have been signed off ministerialy by all departments. They've all said they agree with what we're going to do," Chant said.