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Since forever, Google has started offering "Private" or "off-the-record" conversations in its GTalk interface. A naive reading of this would indicate that GTalk finally has started supporting the OTR protocol over XMPP. A slightly less naive reading would be that the protocol is supported, but that Google reads your conversations anyway, through e.g. mod_otr.

Unfortunately, Google has chosen to be deliberately misleading regarding the encryption of your messages.

If you take the time to actually click the little "read more" link, you are informed that the only difference that a "private conversation" has from a regular GTalk conversation is that Google promises logs won't show up for you or your chat partner.

...yeah, not even promising not to log and/or analyse them for themselves..

So, off-the-record GTalk is not actually Off-The-Record messages. And, since the GTalk servers are still not capable of encrypted server-to-server connections, this means that you have no way of securing your messages against various surveillance outfits who do not already have direct access to the Google servers.

However, by using third-party clients, such as Jitsi, Pidgin, Adium or Trillian, you can still use proper OTR to achieve encrypted conversations over GTalk. For Android, both Xabber and Gibberbot are reasonable alternatives with OTR.

TL;DR: GTalk "off-the-record" isn't. Use a third-party client.