|Scenario Task Description=If you want to have a private chat conversation with someone, you need to make sure that no one else but you and the person/s you are chatting with can read your messages (confidentiality), that the person/s you are chatting with are really who they say they are (authenticity) and that what you and the other people in the chat are writing is not tampered with by third parties (integrity).
In order to obtain all this, you need to use a tool offering end-to-end encryption and key verification. As most service providers (e.g. Google, Microsoft, Yahoo, Facebook) don't offer this service and can therefore read your chat record, it is a good idea to either switch to an alternative chat service that provides encryption by default, or to use software for encryption if you need to stick to those services. Take a look at the EFF's [https://www.eff.org/secure-messaging-scorecard Secure Messaging Scorecard] from EFF to see how they rate various chat clients that claim security properties.
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The standard for a secure two-party conversation is called [https://en.wikipedia.org/wiki/Off-the-Record_Messaging OTR - Off the record messaging], and several popular chat clients support it, including Pidgin with OTR for [https://securityinabox.org/en/guide/pidgin/windows Windows] and [https://ssd.eff.org/en/module/how-use-otr-linux Linux], [https://ssd.eff.org/en/module/how-use-otr-mac Adium] for Mac, and [https://securityinabox.org/en/guide/jitsi/windows Jitsi] for all common desktop operating systems. The latter also includes secure audio and video conferencing. These clients can work with your existing accounts on Google, Facebook, Yahoo, etc. and encrypt the conversation over their respective networks.