| 221 | return preset |
| 222 | |
| 223 | def compute_fixed_info(self, headers, bit_size): |
| 224 | # AlgorithmID |
| 225 | if self.key_size is None: |
| 226 | alg_id = u32be_len_input(headers["enc"]) |
| 227 | else: |
| 228 | alg_id = u32be_len_input(headers["alg"]) |
| 229 | |
| 230 | # PartyUInfo |
| 231 | apu_info = u32be_len_input(headers.get("apu"), True) |
| 232 | |
| 233 | # PartyVInfo |
| 234 | apv_info = u32be_len_input(headers.get("apv"), True) |
| 235 | |
| 236 | # SuppPubInfo |
| 237 | pub_info = struct.pack(">I", bit_size) |
| 238 | |
| 239 | return alg_id + apu_info + apv_info + pub_info |
| 240 | |
| 241 | def compute_derived_key(self, shared_key, fixed_info, bit_size): |
| 242 | ckdf = ConcatKDFHash( |