I'm designing an application in which clients generate their own TLS certificates ad-hoc (there's no central authority).

When two clients interact for a first time, I need for them to mutually check their peers' certificate. I know that fingerprints are generally used for this, but I need to keep this more newbie-friendly, hence having them check 20 hex characters (SHA-1) doesn't sound very convincing.

I though about representing the same fingerprint with the characters 0-9a-zA-Z (giving me 62 characters to represent the same value), but it's still 13 digits long.

Is there any common (or maybe not as common) way of having two users validate their mutual certificates? This is a real time, low-latency application, so multiple round trips are possible.

EDIT
Users can exchange information in person in this scenario, so saying (or showing) a code to one another is possible. However, I'd like to avoid them having to eyeball 20 characters and manually check them, mostly for user-friendliness.