def METHOD_NAME(self, msk, ID):
    _ID = group.hash(ID)
    r = group.random(ZR)
    sk_id1 = msk['g2']**((msk['alpha']+ r * _ID) * msk['D11'] - r * msk['D21'])
    sk_id2 = msk['g2']**((msk['alpha']+ r * _ID) * msk['D12'] - r * msk['D22'])
    sk_id3 = msk['g2']**((msk['alpha']+ r * _ID) * msk['D13'] - r * msk['D23'])
    sk_id4 = msk['g2']**((msk['alpha']+ r * _ID) * msk['D14'] - r * msk['D24'])
    k = { 'sk_id1':sk_id1, 'sk_id2':sk_id2, 'sk_id3':sk_id3,
          'sk_id4':sk_id4 }
    if(debug):
        print("Generate User SK...")
        group.debug(k)
    return k