feat: construct class for dsum

[vivianjeng]

DSum

• $KeyGen()$:
  • $(pk,sk_{pk}) = ((NIKE.pk, AoNE.pk),(NIKE.sk_{pk}, AoNE.sk_{pk}))$
• $Encrypt(sk_{pk}, m)$:
  • $c_{pk} = x +\sum_{pk' < pk}r - \sum_{pk' > pk}r$
  • $ct_{pk} = (AoNE.Encrypt(AoNE.sk_{pk},(c_{pk}, U_M, l)), U_M, l)$
• $Decrypt(\epsilon, (ct_{pk})_{pk\in U_M})$
  • $AoNE.Decrypt(\epsilon, (ct_{pk})_{pk\in U_M} )$
  • return $\sum_{pk\in U_M} c_{pk}$

[vivianjeng]

TODO:
#3 #4