Inconsistent SSID Lengths Due to Variable id Length in ComputeSSID

[B08902060]

The current implementation of the ComputeSSID function can lead to inconsistencies in the length of the generated SSID. This issue arises because the id parameter can have a variable length, resulting in SSIDs of varying lengths. Consequently, this can cause the SSID and ZKSsid lengths to be inconsistent, which has been observed to cause failures in verifying the Pedersen parameter proof during the resharing process.

Additionally, during the Reshare phase, the id used to compute ssid is derived from dkgResult.Bks[selfId].String(), generated during the DKG phase.

Is there any special significance to the current implementation, or can I use padding to address this issue?

[B08902060]

I am working on fixing this issue because I encountered the same error mentioned in a previous issue: #233. To address this, I attempted to resolve the problem by fixing the input string length of ZKSSID, specifically for bks.x.

alice/crypto/birkhoffinterpolation/birkhoffinterpolation.go

Line 62 in c36bd58

return fmt.Sprintf("(x, rank) = (%s, %d)", p.x, p.rank)

You can review the changes in the comparison below:

    return fmt.Sprintf("(x, rank) = (%078s, %d)", p.x, p.rank)

Fix bks.x length (with testcase)
Is this approach feasible?