confirmed_transcript_hash_[0] = ""; /* zero-length octet string */
interim_transcript_hash_[0] = ""; /* zero-length octet string */

confirmed_transcript_hash_[epoch] =
    Hash(interim_transcript_hash_[epoch - 1] ||
        ConfirmedTranscriptHashInput_[epoch]);

interim_transcript_hash_[epoch] =
    Hash(confirmed_transcript_hash_[epoch] ||
        InterimTranscriptHashInput_[epoch]);