The Canadian manufacturer of Blackberry mobile phones has rejected demands by the Indian government that it help decrypt suspicious text messages.
Research in Motion says its technology does not allow any third party - even the company itself - to read information sent over its network.
The Indian authorities have been reluctant to allow the widespread use of Blackberries in the country.
They fear militants and criminals may take advantage of the secure system.
A number of other countries around the world have expressed similar fears.
"The Blackberry security architecture for enterprise customers is purposefully designed to exclude the capability for Research in Motion (RIM) or any third party to read encrypted information under any circumstances," the company was quoted by Times of India newspaper as saying.
The Indian government's department of telecommunication and the security agencies have asked the Canadian firm to provide the master key so that they can access the contents transferred between the handheld devices.
In India, Blackberry services are provided by Bharti Airtel, Reliance Communications, Vodafone and BPL Mobile.
The country has only about 115,000 Blackberry customers at the moment, but it is a rapidly growing market.