[zmanian]

You can use a "blockchain", an enforcer of security deposit against double spending rather than as the raw double spend prevention mechanism.[0]

[0] https://eprint.iacr.org/2016/1033

[schoen]

"Soothly we live in mighty years!"

It looks like the underlying mechanism that they use for this was described in

https://dl.acm.org/citation.cfm?doid=2810103.2813686