It should be noted that this is not generally something that is associated with the kink scene. You may consider it to be “kinky,” and that is a matter of opinion. However, in the kink scene we tend to be very picky about our play partners because we have specific scene ideas and play preferences that are best complimented by a certain sort of person. A person who identifies as a “Little” will be best complimented by someone who enjoys playing the role of “Daddy,” for example. This means we are very unlikely to chose partners in any sort of random way.
The idea behind a “key party” is that several couples get together at someone’s house and have dinner and drinks. At the start of the night, all the men put their keys in a bowl. At the end of the night, each women picks a set of keys from the bowl, and goes home with whomever they belong to.
This is typically popular among older married couples who are vanilla, because a marriage can get stale, and vanilla people all have pretty much the same kind of sex, so they can pretty much match up with any other vanilla person.
Of course, I have been to a key party because they are sometimes organized within the BDSM community. But when that is the case, it is usually among couples who know one another. It will be something like all female Dommes and all male Submissives, and everyone will fill out consent forms and BDSM checklists first.
Obviously, as I have said many times before, spontaneous hookups are a bad idea. Remember that condoms do not protect against HSV-1 or HSV-2 and are not 100% for other STDs either. Anytime you “hook up” without first trading current STD tests, you put your life and the lives of your partners at risk. So before you go organizing your own kink key party, make sure to get the paperwork of everyone involved.