Welcome to Hash For Vouch!
Webmentions are a simple way to notify any URL when you link to it on your site. Vouch is an anti-spam extension to Webmention; in particular, when one sends a webmention, one can also include a "vouch": a URL which links to your post and is trusted by the site you're mentioning, as evidence that you're worthy of trust.
But it is sometimes difficult to find a vouch link, and Vouch has the clique problem: it's useful among a group of people who all know one another and who know that they know one another, but it can be unreasonably hard to join the conversation if you're not known by the group.
The Vouch spec itself says that it's important to "shift the burden to the sender": "Typical protocols susceptible to (abused by, made nearly useless by) spam (e.g. SMTP, Pingback, Trackback) make it very easy for the sender to send, and thus put all the burden of dealing with filtering undesired senders on the receiver." So, what if it were more difficult to send, but without requiring the "playground politics" of having to find a way into the clique?
Hence, Hash for Vouch. If you prove that you're prepared to do a small amount of work, then Hash for Vouch will vouch for you when you send a webmention. This work basically means that sending a webmention will take you a few seconds longer; that isn't too onerous for you, but it is prohibitive for spammers who can't spam if sending webmentions takes a few seconds rather than thousands every second.
You can use the form below to ask Hash for Vouch to vouch for a webmention that you plan to send, or if you're technically adept you can use Hash for Vouch's API to add Hash for Vouch integration directly into your code.