[tenthirtyam]

IIRC it is possible to have some clever encryption so that the person you sent your message to can prove to their own satisfaction that it came from you, but they cannot prove to anyone else that it came from you. Which gives you plausible deniability; you can always claim that your contact forged the message.

Can't remember what the algorithm is called.

[upofadown]

No particular name. Just deniability. I personally like to call this particular scheme, deniability through claimed forgery. Not particularly clever. You just provide your correspondent with what they need to forge your messages after the end of the session.

I don't know if it actually could work in practice:

https://articles.59.ca/doku.php?id=pgpfan:repudiability

[gabrielhidasy]

Isn't the scheme simply agreeing in a shared key and both using it? I'll know that the message is from you if it's signed with that key and is not from me and vice versa, but neither of us can prove who created the message.

[XorNot]

Off The Record chat did this.

https://en.wikipedia.org/wiki/Off-the-record_messaging