NEW YORK (CBSNewYork/AP) — Police Commissioner Bill Bratton says the possibility that the Islamic State group is using encrypted apps to communicate is a “cause for concern.”

Bratton said intelligence investigators monitor social media and other ways ISIS frequently recruits and communicates, but said that’s being thwarted by encrypted apps, 1010 WINS’ Juliet Papa reported.

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“One of the most fruitful avenues, which was our ability to potentially listen in, has been closed in a very significant way,” Bratton said Tuesday.

While there has been no hard evidence so far that the Paris extremists relied on encrypted communications — encoded digital messages that can’t be read without the proper digital “keys” — Bratton has said he believes such messaging systems will prove to have been “a significant factor” in planning the attacks.

So-called end-to-end encryption technology is now widely used in many standard message systems, including Apple’s iMessage and Facebook’s WhatsApp. Similar technology also shields the contents of smartphones running the latest versions of Apple and Google operating software.

Strong encryption is used to protect everything from corporate secrets to the credit-card numbers of online shoppers to intimate photos and secrets shared by lovers.

Bratton said encrypted communications and court decisions blocking many wire taps are making it tougher to monitor what terrorists and cyber criminals are up to.

“We will continue to try to seek additional legal ways to gather information,” he said.

Security experts are also concerned that Sony’s PlayStation 4 has become a communication tool for terrorists. Investigators say ISIS may be using the game console to pass messages, which are difficult to track.

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“It’s a huge, huge problem,” said former FBI Director Timothy Murphy.”Social media recruitment, social media radicalization, and then they’ll go off those social media platforms, into encrypted platforms to have further conversations about travel, about if you can’t travel, take action against your own country.”

Bratton said there is no information to date indicating that those suspected in the Paris attacks have had any communication with groups or individuals here, Papa reported.

He said he plans to have conversations with New York’s political leaders to find what he called more common ground with the manufacturers of the encrypted products, WCBS 880’s Rich Lamb reported.

“To meet our needs while at the same time responding to some of their needs to stay competitive and meet public demand,” he said.

Often, even the app makers can’t get the data because messages self destruct or the encryption key constantly changes.

“I now think we’re going to have another public debate about encryption, and whether government should have the keys, and I think the result may be different this time as a result of what’s happened in Paris,” former CIA deputy director Michael Morell said Monday on CBS This Morning.

On Monday, Attorney General Loretta Lynch said the government continues to have “ongoing discussions” with industry about ways in which companies can lawfully provide information about their users while still ensuring their privacy.

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