Encrypting phone calls makes life difficult for crime investigators, possibly allowing offenders to escape justice, the FBI chief has warned.
Speaking during an event at the Brookings Institution in Washington, the USA, the FBI director James Comey warned that advanced encryption features available on new Google and Apple smartphones have "the potential to create a black hole for law enforcement."
Designed to prevent unauthorised persons from accessing data stored on the devices, the encryption systems would also prevent electronics companies from retrieving the data when requested by FBI agents based on a court order.
Comey said FBI agents have come across a growing number of cases they believe evidence sat on a phone or a laptop which they were unable to crack, though did not provide specific examples.
"If this becomes the norm, I suggest to you that homicide cases could be stalled, suspects walked free, child exploitation not discovered and prosecuted," he said.
Public demand for encryption technologies has grown following revelations made by former US National Security Agency contractor Edward Snowden about the US government’s widespread spying practices.
Claiming that public concerns about public mass surveillance were unsubstantiated, Comey said that although mobile phone encryption makes a good marketing pitch, it could have very serious consequences for all levels of law enforcement.
Comey also urged the US Congress to update the law that governs law enforcement's ability to intercept communications, which was enacted two decades ago and does not address some newer technologies.