Function repairShareStep2

repairShareStep2(ciphersuite: Ed25519Sha512Impl, deltas: Delta[]): Sigma
Step 2 of RTS.

Generates the "sigma" value from all deltas received from all helpers. The "sigma" value must be sent to the participant repairing their share.
Parameters
- ciphersuite: Ed25519Sha512Impl
  The Ed25519Sha512 ciphersuite instance
- deltas: Delta[]
  Array of Delta values received from all helpers
Returns Sigma
The computed Sigma value
- Defined in ed25519/src/keys/repairable.ts:87