Chapter 384: The Answer Pair

The first six exchanges worked, but the bellkeeper refused to treat that as proof of anything beyond basic competence.

"It would be embarrassing if two trained keepers couldn’t tune against one another."

Rias recorded the sixth success and closed the baseline set.

Each opening had been different. The Sairren stationed at the distant relay listened, produced the necessary response, and waited for the local keeper to accept it. Martin could barely distinguish one exchange from another, while Elisebeth could sense differences in the magical resonance but admitted she did not understand the Sairren logic behind them.

Only the bellkeepers could interpret the answers well enough to judge them.

Once the sixth legitimate exchange finished, Mireva looked toward Rias.

"Test the recordings."

A third Sairren waited in the adjoining chamber. He had access to every successful response produced so far, but he did not know what opening the local bellkeeper would choose next. His job was simple: replay something genuine and see whether familiarity alone could fool the receiver.

The new opening rang.

Before the legitimate distant keeper answered, the third Sairren replayed the response from the second test.

The bellkeeper beside Martin remained motionless.

"Wrong?" Mireva asked.

"Completely."

Rias checked the recording.

"The timing was almost identical to the original."

"The timing wasn’t the problem."

They tried again with a different opening and another previously successful response. It was rejected, and a third attempt failed as well.

Rias updated the record.

"Three recorded responses rejected against new openings."

The legitimate distant keeper answered the next challenge, and the local relay accepted him immediately.

Alexandra sat on a stone ledge with Kumoe crowded around her legs. The curious head had started investigating Katherine’s medicine pouch again, but the right head caught her by the neck and pulled her back before Katherine needed to move it.

Alexandra stroked them both while watching the test.

"How long before someone learns enough to imitate the right answer?"

The room lost what little amusement it had.

The route-keeper walked over to the recorded pairs.

"We don’t know. If an enemy hears enough openings and enough correct responses, they may begin recognizing how a keeper builds the return."

Rias added that uncertainty to the record.

The route-keeper continued. "There is another problem. A correct response proves the person understands the resonance. It does not necessarily prove they’re standing at the relay we think they are."

Mireva’s ears lifted.

"You mean the signal could be carried somewhere else."

"Perhaps. We haven’t tested whether that can be done."

Rias recorded it exactly that way.

Cassandra had remained near the rear of the chamber, watching the Sairren work. "What if the relay itself is taken?"

The route-keeper looked toward her.

"Then this becomes much less useful."

"A captured keeper could still answer correctly."

"Yes."

Cassandra looked toward the tuning forks.

"So the challenge proves knowledge. It doesn’t prove the person answering is free."

The bellkeeper considered that.

"Correct."

The limitations were accumulating quickly. A live challenge helped against recordings, but it did not solve captured keepers, occupied relays, physical access, or whatever remained active in the Lower Belfry. It also did not prove that enough observation could never teach someone how to imitate the response.

Mireva looked toward the maintenance equipment.

"For the calls that matter most, I want something they cannot get by listening."

The route-keeper had already started searching through a tray of bronze pieces.

"We physically verify couriers now. We could carry part of the proof instead of sending all of it through resonance."

He and the bellkeeper began discussing the idea in technical language that quickly lost everyone except the Sairren. Martin stopped trying to follow every term and watched them work instead.

The route-keeper eventually selected a narrow bronze repair strip.

"What if both staffed relays receive one part of something prepared together?"

Mireva looked at him.

"A physical token?"

"Something close to one."

Rias considered the obvious implementation.

"One pair for a shift?"

The bellkeeper rejected it.

"Too long. If one piece is stolen, every later call using it becomes suspect."

The route-keeper agreed.

"One important call, one pair."

It was expensive and inconvenient. Mireva did not object.

The bellkeeper cut the bronze strip in half along an uneven line. He handed one piece to the route-keeper and kept the other, then they struck both against the relay frame.

Martin heard a faint metallic note, but every Sairren in the room reacted more strongly.

Mireva stepped closer.

"The break changes the resonance."

"Pieces from the same break carry the same imperfection," the bellkeeper said. "At least in theory."

Rias examined the edges.

"Can you identify that over distance?"

"Maybe."

They tried.

The distant keeper could hear the first bronze response but could not reliably distinguish it from another piece of similar thickness. Rias recorded the failure while the bellkeeper changed how the strip was struck, yet the second attempt remained uncertain.

The route-keeper frowned, carved a shallow notch near the broken edge, and tested both halves again.

The bellkeeper stopped him.

"Now you’ve changed the test. If it works, we won’t know whether we heard the fracture or the notch."

The route-keeper stared at the bronze for a moment, then discarded the pair and started again.

The third pair used one clean strip, one irregular break, and no additional markings. Both keepers tested the pieces locally before one half was carried physically to the distant tower.

Once the courier returned, the live exchange began.

The opening traveled first.

The response came back.

Then both bronze halves were struck.

The local bellkeeper listened closely.

"Accepted."

After two failures, one success earned another test rather than celebration.

Mireva pointed toward the third Sairren.

"Give him one half from another prepared pair."

The false keeper now possessed legitimate physical proof but still lacked the correct response to the live challenge.

He tried.

Rejected.

Then they reversed the problem. He received the response from a previous successful exchange but carried the wrong bronze half.

Rejected again.

The bellkeeper finally allowed himself a small smile.

"Better."

Rias wrote that word rather than anything stronger.

Alexandra leaned forward.

"If somebody steals the correct half and knows the response?"

"Then that call may be compromised," the route-keeper said.

Cassandra added, "And the courier carrying the pieces can be intercepted before the call ever happens."

Mireva nodded.

"Then physical verification stays part of the risk. We haven’t removed it. We’ve only made one stolen sound less useful."

She studied the table for several seconds before looking back at the Sairren experts.

"What can we responsibly use this for?"

"Staffed critical relays," the route-keeper said.

The bellkeeper counted possibilities on his claws.

"Warden redeployment. Healer requests. Supply movement. Maybe a controlled evacuation order between posts that have already been physically verified."

"Not households, children, or ordinary movement," Mireva said.

"Not unless these tests become far more reliable than they are now."

Mireva accepted that answer, then glanced toward Rias. Nothing in the evidence contradicted the bellkeepers’ conclusion.

"Tomorrow we connect one real route. A supply bridge with no residences nearby. Both ends staffed and both keepers physically verified before the test."

The route-keeper nodded.

"And if anything behaves differently from what we observed here, we close it."

Martin looked toward the disconnected relay. They had spent hours proving that one real Sairren could probably recognize another real Sairren under controlled conditions, while also finding new ways the idea could fail.

Martin preferred that to false confidence. After everything the Belfry had survived, nobody here could afford to mistake a small answer for a complete one.