Rumors that President Donald Trump's aides are using an encrypted messaging app called Confide has landed the software firmly in the spotlight and under the security microscope.
The Washington Post on Monday mentioned that Confide, built by a startup in New York City, is used by some White House staffers to gossip in private. The app was billed by the newspaper as "a secret chat app that erases messages as soon as they're read." The aides, fearful of being accused of leaking to the press, turned to Confide in an attempt to cover their tracks and stay off the radar.
This is not the first time Confide has appeared in the national news conversation. In 2014 , the app was pitched to big biz in the wake of the Sony Pictures network intrusion as a safe means to communicate without being bothered by hackers. What was missing from Confide's pitch, however, was much in the way of details about how the application delivered on its promise of secure auto-destructing end-to-end encrypted messaging.
Given that foreign spies, as well as Uncle Sam's own snoops, will now definitely be all over this thing like a sore rash, The Register asked Confide for more info: how does the encryption work, what is done to thwart eavesdroppers, and so on.
And we were told the software, available for iOS and Android, basically uses the OpenPGP standard to perform public-private cryptography, uses AES for ephemeral per-message encryption, and exchanges public keys between users via TLS connections with certificate pinning. To us, this sounds like the public keys travel through Confide's servers: if so, it means the app maker can, or be forced to, eavesdrop on conversations by substituting keys mid-exchange. It does mean, though, that it's tricky for others to intercept and successfully crack messages.
"Confide uses public/private key cryptography with ECDH for key agreement and per-message AES keys to encrypt the message payloads," Confide cofounder and president Jon Brod told ElReg on Tuesday evening.
"In addition, we use recommended best practices to ensure the security of network connections, such as using TLS 1.2 with certificate pinning to prevent against man-in-the-middle attacks."
Using OpenPGP and TLS cert pinning is a solid start, although we weren't told the key lengths. The app's methods are better than the questionable home-brew crypto used in some other chat applications. The software appears to use OpenSSL 1.0.2j, which means it contains any security bugs patched since September 2016 and it isn't FIPS 140-2 validated.
"The encryption appears to operate like most other end-to-end encrypted apps, where public and private keys are generated," said computer forensics expert Jonathan Zdziarski, who studied the Confide app earlier today.
"In the case of Confide, an ephemeral key seems to be in play to encrypt messages themselves with a symmetric cipher. What seems different about this encryption is that it appears to regenerate the public key under certain circumstances. It’s unclear why, but unlike Signal and WhatsApp, which consider it something to alert you about if your public key changes, Confide appears to consider this part of its function.
"Key exchange is always the most difficult part of good encryption routines. Depending on whether or not Confide is able to detect this and warn the user, it’s possible although not confirmed that the application could be susceptible to the same types of man-in-the-middle attacks that we’ve seen theorized in WhatsApp ( if you leave the alerts off ) and iMessage."
Zdziarski continued: "This one’s a tough call ... Ultimately, the application warrants a cryptographic review before I could endorse its use in the White House. If I were the White House’s CIO, I would other than hate my life not endorse any third-party mobile application that didn’t rely on FIPS 140-2 accepted cryptographic routines, such as Apple’s common crypto.
"OpenSSL is very clear about not being FIPS validated, and ultimately it would be up to the manufacturers of Confide to have each individual version of their software validated under FIPS. Nonetheless, as difficult as the FIPS validation process is, should the application not have been validated, it has no place in government, in my opinion.
"The app at least attempts to do what it says it does, and I don’t see any obviously gaping holes. That doesn’t mean its perfect, and obviously has at least a few disagreeable functions such as retaining undelivered messages. On the whole, it may be fine for personal conversation, but I would recommend a more proven technology, such as Signal , if I were to have my pick of the litter."
A spokesperson for the White House was not available to comment on the rumors.