[BUG]on key splitting scheme.

[ALiberalVoluntarist]

Bug Description

Briefly describe the bug/issue you've encountered.

This issue was found on ts-sdk on key splitting scheme. Please read the link below and fix on py-sdk which more likely have a same issue.

[ TOB-BSV-2 ]‬ ‭toKeyShares‬‭ can result in key leakage or unrecoverable‬‭ keys‬ #335
bsv-blockchain/ts-sdk#335

The issues for @jo7ueb

[jo7ueb]

Hi Ken-san, I'm just gonna start my work now.

[jo7ueb]

Original ts codde uses do-while loop which Python doesn't support.
Infinite loop with break steatment can be good alternative, but we need to be careful for loop-exit condition for avoiding "real" infinite loop.
This note is just for myself.

[jo7ueb]

The original pull request does not add a new unit test for this functionality.
This makes it difficult for me to verify that my upcoming porting is appropriate.
Careful revewi should be taken.

[jo7ueb]

@ALiberalVoluntarist please reveiw PR#73 for fix of this vulnerability