right. will fix that.   
```
//sort lexicographically, i.e. as strings, i.e. alphabetically
```
this is a standard? Or just a way to do it? I would prefer to keep ```cosignerWallets``` sorted, to avoid sorting each address generation, therefore, we could sort on lexicographically on the extended master public key. (which could lead that keys(n) will not be sorted by themselves).