Net administrative body Icann put its plans on hold after it emerged that some ISPs and large firms were not ready to make the change.

It feared that tens of millions would lose net access if the change went ahead as planned on 11 October.

Icann said it was working with ISPs to update software and ensure everyone is ready to switch next year.

"It would be irresponsible to proceed with the roll [out] after we have identified these new issues that could adversely affect its success and could adversely affect the ability of a significant number of end users," said Goran Marby, head of Icann.

Trusted information

Since early 2017, Icann (The Internet Corporation for Assigned Names and Numbers) has been preparing to update the cryptographic keys used to ensure that information about web domain names can be trusted.

The Domain Name System Icann oversees can be thought of as the net's address books and they help to turn the written names for websites that humans use into the numeric equivalents that computers prefer.

Many organisations have turned to a secure version of DNS, known as DNS SEC, because it helps them avoid many attacks cyber-thieves use to hijack traffic to popular sites. About 750 million people browse the web using information provided by DNS SEC servers.

Icann has been distributing new keys to DNS SEC users for months. It planned for all of them to start using the new keys on 11 October.

But an investigation by the net admin body found that many organisations were running versions of DNS SEC that had not updated properly or did not have the new keys in place ready to use. It said it was not clear why some versions of DNS SEC had not been updated as expected.

Icann has now started contacting ISPs and firms that were not ready to ensure their software is updated as expected. No fixed date has yet been given for when the new keys will be used but it said it hoped it would be completed by the end of March 2018.