When trying to use the putMutable functionality of a link instance, the library throws an exception.

The problem is at line 239, where ed.sign is called but ed is not defined.

I guess an import of ed25519-supercop was missed here.

It could be bypassed by declaring a global.ed = require('ed25519-supercop') in a previous part of code, but I believe this is bad practice and it has to imported here locally.