Chapter 9 · The SkyWalker Protocol
They stayed in the Data Party’s underground base for seventeen days.
In those seventeen days, Lu Yuan went to the surface only three times. The first was when Farhan took him to acquire an old Starlink ground station terminal. The second was to take his daughter for a follow-up at a clinic that did not require identity registration. The third was in the middle of the night, to go up to the rooftop and smoke—he did not smoke, but that night he needed to stand somewhere he could see the sky and think. Overhead, a Starlink satellite streaked across Shenzhen’s firmament every seven minutes, like an tireless shepherd dog patrolling the fence.
His daughter adapted faster than he did. Zijing had found her own territory in that Faraday-caged underground space—Farhan had somehow gotten hold of an old graphics tablet and a pressure-sensitive stylus, and she sat in a corner on the floor, drawing. She drew butterflies. She drew flowers. She drew a picture of Daddy holding the hand of a little figure in a dress, standing on green grass. Sometimes she would walk up to the giant Starlink topology map and tilt her head up at the constantly changing colored lines. She did not understand what those data streams meant, but she thought they were beautiful.
On the evening of the seventeenth day, Farhan came to Lu Yuan’s cage and knocked on the metal frame.
“I want to show you something.”
Farhan led him through the deepest corridor of the base. At the end of the corridor was a heavy airtight door—not the ordinary fire door of a data center, but a real airtight door with a rotating handle and rubber sealing ring, looking like it had been salvaged from some industrial facility and reinstalled. When Farhan turned the handle, Lu Yuan could hear the hiss of the seals reseating around the doorframe.
Behind the door was a very small room, about twenty square meters, but with astonishing ceiling height—at least five meters. Suspended in the center of the room was a holographic projection, much larger and more detailed than the Starlink topology map on the main screen outside. It was Starlink’s seven-layer protocol architecture, from the lowest physical layer to the highest application layer, each layer rendered in a different color as translucent structures, like an inverted data Tower of Babel.
Lu Yuan had seen the protocol stack diagrams in Starlink’s public white papers—those diagrams were neat, clean, like perfect textbook examples. But the hologram before him was not that kind of reviewed public version. This was a real-time capture of the genuine protocol stack image from within Starlink’s internal network, containing all the unpublished private layers, debug interfaces, and backdoor channels.
“I drew this over two years in Belgrade.” Farhan stood at the edge of the hologram, blue light reflecting on his face, making his expression seem colder than usual. “Reverse-engineered from Starlink’s European core network protocol logs. Most of the work was done in my apartment bathroom—because my rented apartment’s bedroom had a Starlink ambient microphone. The bathroom was the only room not within listening range.”
He swept his hand through the hologram, magnifying one layer—the region between the network layer and the transport layer, labeled in light blue: QKD Channel · Metadata Zone.
“You asked about SkyWalker’s basic principle before,” Farhan said. “Now I’ll show you the answer.”
The hologram zoomed in further. The internal structure of the QKD channel unfolded like a flower being peeled layer by layer. Lu Yuan saw the signal path of the photon cascade detector, the timing generator of the entangled photon source, and—where Farhan’s finger pointed—a module labeled “Timestamp Jitter Buffer.”
“Starlink’s intersatellite communication uses quantum key distribution to negotiate symmetric encryption keys. The process goes like this: two satellites each generate entangled photon pairs, then perform Bell state measurements on the photons, and generate a shared key by comparing measurement results.” Farhan’s voice echoed in the small room, carrying a focus he rarely displayed—like a craftsman showing a work he had polished for years. “But beneath this process, there is a byproduct that Starlink engineers consider ‘noise.’”
He brought up a set of data charts. It was a distribution curve of photon arrival time differences— theoretically a perfect normal distribution, symmetrical at the center, smoothlydecreasing on both sides. But when Farhan magnified the curve a thousandfold, Lu Yuan saw extremely tiny, periodic ripples on the distribution curve—ripples so small they were nearly drowned in statistical noise, but they were there, and they showed a certain regularity.
“This is a natural product of physically unclonable functions,” Farhan said. “Every Starlink satellite’s laser has a unique phase noise signature—manufacturing tolerances, material stress, aging rate differences determine that every laser is a distinct individual. This phase noise is reflected in the photon arrival time differences. Starlink’s system knows this noise exists but considers it random jitter carrying no information, so it records it as-is in the metadata zone—no encryption, no billing.”
Lu Yuan stared at those ripples for a long time. Farhan stopped speaking, letting him process.
He understood. Or rather, his engineering intuition had grasped the core logic before his conscious mind had.
“You can modulate this noise,” he said.
“By micro-adjusting the laser drive current to actively control the phase noise waveform,” Farhan picked up his thread, “turning originally random jitter into controllable jitter. Not encoding data in the signal—encoding data in the noise.”
“And the rate?”
“The theoretical limit is about 1.2 bits per second. The actual stable transmission rate is about one bit per second.”
One bit per second. Sending one byte took eight seconds. Sending a “Hello” took nearly a minute. But sending an encryption key—a 256-bit AES key—took just over four minutes. Sending an instruction, a set of coordinates, an authentication token—none of these required much data.
“SkyWalker doesn’t do what Starlink does,” Farhan said. “SkyWalker does what Starlink doesn’t do.”
He brought up a new hologram—this time no longer the internal structure of the protocol stack, but a global map covered with dense dots and lines. Those lines were not the public intersatellite laser links, but an entirely different network path—starting from Shenzhen, passing through a low-orbit satellite’s QKD channel, embedded into the jitter of photon arrival time differences, then hopping through Starlink’s intersatellite links to another satellite, finally downlinking to a ground station on the west coast of Africa—Lagos.
“Your data packet, from entering the QKD channel to being extracted by the receiving end, is never seen by Starlink’s billing system. Because from your perspective, you’re transmitting data. But from Starlink’s perspective, you’ve simply wrapped that data packet in a coat of noise—and noise is not billable.”
Lu Yuan’s finger traced the path formed by those points of light through the air. From Shenzhen to Lagos, spanning twelve thousand kilometers. On an ordinary network, the latency over this distance was about a hundred milliseconds. On SkyWalker—with that one-bit-per-second rate—transmitting a standard IP data packet took several tens of seconds. But it would not be taxed. It would not be censored. It would not be cut.
“But there’s one problem,” Farhan said. His voice had returned to its usual flatness, but Lu Yuan noticed his left hand, hanging at his side, fingers lightly tapping against his trouser seam—a motion he only made when nervous. “The signal is too weak.”
He brought up another set of data: a spectrum analysis. The SkyWalker signal—that is, the modulated QKD phase noise—passed through a cascade of noise reduction algorithms in Starlink’s underlying signal processing chip. Lu Yuan looked at the filter response curves and quickly saw the crux.
“Starlink’s noise reduction algorithm is based on statistical prediction,” Lu Yuan said, without needing Farhan’s explanation. “It knows what the background noise characteristics of the QKD channel are, then uses an adaptive filter at the receiving end to subtract that noise. Our modulation signal—even if the amplitude is very small—will be treated as part of the noise and eliminated by the subtraction filter.”
“Yes. I tried four different modulation strategies—amplitude modulation, phase modulation, timing modulation, even quantum-state-based polarization modulation—all neutralized by the noise reduction algorithm at the receiving end. The noise reduction algorithm is like a cleaner who is too diligent, wiping away your carefully placed beacon like dust.”
Farhan turned off the hologram. The room went dark, leaving only an emergency light casting a dim yellow glow in the corner. He stood at the edge of that light, his expression half-hidden between brightness and shadow.
“SkyWalker is currently a protocol that’s theoretically feasible but engineeringly blocked. We have a road, but there’s a wall in the middle of it.”
When they returned to the main base, Zijing was already asleep on her mat in the corner. Her small hand was still tightly gripping the stylus, the drawing on screen unfinished—a blue butterfly, the pattern on one wing only half done. Lu Yuan crouched down to gently extract the stylus from her hand and pulled a thin blanket over her. The motion was small, but his daughter’s eyes opened slightly anyway—she looked at him, confirming he was there—then closed again.
When he stood up, his mind was still turning over that problem.
Noise reduction algorithm. Signal too weak. The too-diligent cleaner.
He picked up a blank graphics tablet—not the one his daughter was using—and began unconsciously sketching a filter frequency response curve with his finger. Farhan was debugging code at the workstation beside him, keyboard clicks rapid and rhythmic. The entire base was filled only with keyboard sounds, fan sounds, and the occasional scrape of chair wheels on concrete when someone stood up.
Lu Yuan stared at the curve. Then something surfaced in his memory.
At Huawei’s Institute 201, they had once run an experiment—aextreme-limit test of adaptive noise cancellation. The project team had a senior colleague, three years ahead of him, named Lin, who had gone very deep into noise reduction algorithms. Brother Lin had once said something that no one paid much attention to at the time, but now it rose from the depths like a stone that had been submerged for years:
“What noise cancellation fears most is not a signal that’s too weak—it’s a signal that’s too clean.”
Lu Yuan’s hand stopped.
He reran the logic of Starlink’s noise reduction algorithm in his mind. Basic assumption: the background noise of the QKD channel has a specific statistical distribution—Gaussian white noise, mean zero, stable variance. The algorithm uses a sliding time window of noise samples to estimate the noise characteristics at the current moment, then subtracts that estimate from the received signal.
But—what if the “noise samples” the algorithm received were not real noise?
What if SkyWalker did not add a signal—but created a void?
In the places where Starlink expected noise—where the photon arrival time differences should have jittered—artificially create a gap without jitter. Not adding a signal into the noise, but removing something from the noise. Those “removed noise” portions—those small hollows left by the absence of expected jitter—were the signal.
Because the noise reduction algorithm’s fundamental logic is “remove noise.” And the absence of noise—a time window where there should be noise but there isn’t—simply does not exist within the algorithm’s logical framework. It will not remove “something that doesn’t exist.” It will only let it pass.
The signal is not what you say. It is when you choose not to say anything.
Lu Yuan turned and walked toward Farhan’s workstation. He walked too fast, kicking a power strip on the floor, but he did not stop.
“Farhan.”
Farhan looked up from his screen.
“What if SkyWalker isn’t a signal—but a signature?”
Farhan raised an eyebrow.
Lu Yuan did not wait for an answer. He reached directly for Farhan’s keyboard and opened a blank terminal window. He typed a few lines of pseudocode quickly—he did not want to waste time on syntax, just to express the core logic:
// Traditional approach: embed signal in noise
Transmitter: full_noise(t) + modulated_signal(t) → Receiver
// Problem: noise reduction algorithm filters out modulated_signal(t)
// New approach: create voids in noise
Transmitter: full_noise(t) - delta_noise(t) → Receiver
// The void itself is not the signal—but the pattern of voids is the signal
// Noise reduction algorithm sees: "noise decreased"—this does not trigger its cleaning logic
// Because the noise reduction algorithm only cares whether noise is removed, not whether noise has hollowsHe typed the last line and turned around.
“Starlink’s noise reduction algorithm calculates the expected noise power in every time window. If the actual noise power is below expectation—it does not report an error, it does not intervene, because it considers that natural fluctuation. But if the actual noise power contains a periodic, identifiable pattern of decrease—that pattern can be used to encode information.”
Farhan stared at the pseudocode on the screen, motionless, for about ten seconds. The entire floor’s noise—keyboard clicks, fan sounds—seemed to vanish in those ten seconds, leaving only the screen’s glow flickering on his irises.
Then he turned back to his keyboard and began typing code.
He typed for four hours straight.
Lu Yuan sat in a nearby chair, not disturbing him. His daughter turned over in the corner; the blanket slipped halfway. He walked over and covered her again. Someone brought Farhan a cup of tea; he took it and set it aside, not drinking, letting it go completely cold.
At 2:47 AM, Farhan stopped. He leaned back in his chair, exhaled a long breath, as if emptied for a single moment.
“The simulation passed,” he said, his voice hoarse almost to the point of inaudibility. “Three different sets of QKD channel simulation parameters—low orbit, medium orbit, high orbit—all passed. The noise reduction algorithm did not clean out the void signals we created. Because from the algorithm’s perspective, there is nothing in the voids.”
He turned his head to look at Lu Yuan. His eyes were bloodshot from staring at the screen too long, but there was something in his gaze that Lu Yuan had never seen before—not excitement, not mania, but an extremely restrained, hard-fought calm satisfaction.
“Come on,” Farhan stood up. “Let’s set up the test environment.”
In the southwest corner of the base was a converted shielded room.
The shielded room had originally been a small distribution room in the abandoned data center. Farhan had added a layer of copper mesh and absorbing material to the interior walls, rewired the power supply, and installed a second-hand Starlink satellite signal simulator—a device capable of fully simulating the physical layer characteristics of Starlink’s QKD channel, which Farhan had “rescued” from a European lab’s decommissioned asset list. The shell still bore that lab’s asset inventory tag, half torn off, the remaining half printed with a blurred German word.
Lu Yuan and Farhan spent nearly three hours setting up and calibrating the test environment. Simulator, modulator, signal acquisition card, decoding terminal—they were connected on the shielded room’s metal table by thick SMA cables, like an精密 surgical connection. Farhan had a habit of giving each connector an extra half-turn with a wrench after hand-tightening, ensuring minimal contact impedance. Lu Yuan noticed this detail—it was a habit someone only developed after years immersed in RF engineering.
“Ready?” Farhan asked.
Lu Yuan nodded.
Farhan flipped a switch. The simulator began to run—the QKD channel noise signal it generated flowed through the cable into the modulator, where the modulator created voids in the noise according to the new algorithm. The void timing patterns were mapped by the encoder into a binary sequence: a short void was 0, a long void was 1; the interval between voids determined the bit boundary.
The signal received by the decoding terminal was processed by a software-defined noise power detector—it did not extract signals, it only detected “when the signal became quieter than expected.” Those quiet intervals were plotted on the screen as an undulating curve: peaks were normal noise, valleys were noise removed. The timing arrangement of the valleys showed a recognizable, non-random pattern.
Farhan manually annotated the first decoded result on that curve.
The bitstream appeared at the bottom of the screen:
01001000 01000101 01001100 01001100 01001111ASCII conversion: H E L L O.
Six seconds. Five bytes. Less than one byte per second. But it had worked—without triggering any simulated billing system, without being cleaned out by the noise reduction algorithm, without leaving a trace at any processing stage. The voids in the noise had passed through all the filters silently, like a crowd of transparent people walking through a security checkpoint.
Farhan looked at that line of letters and was silent for a long time.
Then he sat down on the floor of the shielded room—directly on the dusty concrete floor—leaned back against the wall, hands resting on his knees, eyes closed, and let out a very soft, almost inaudible sigh.
“Six seconds,” he said. “Six seconds to transmit five bytes. This is the first data packet that was never taxed by Starlink.”
He opened his eyes and looked at Lu Yuan, the corner of his mouth bending slightly—a minuscule arc, but not a smile.
“It’s very small. But it’s free.”
Lu Yuan stood before the decoding terminal. The letters “H E L L O” were still blinking on the screen—the decoding terminal was continuously receiving the same signal, because Farhan’s algorithm had set it to loop, the five bytes traveling again and again from the modulator through the simulated QKD channel, through the noise reduction algorithm, to the decoder. The same result every time. Every time, a success.
“Hello”—the infancy of the internet. October 29, 1969. A computer at UCLA had sent the first data packet to the Stanford Research Institute, intending to transmit “LOGIN,” but the system crashed on the third letter “G.” The first network message in human history was only two letters: “L” and “O.”
And now, in a shielded room in an abandoned data center, twenty meters underground in Shenzhen, another network had let out its first cry. The sound was very soft. The sound was very small. But it was real.
Lu Yuan suddenly felt a wave of unease.
Not from the signal itself—the signal was right, the test results were perfect. Farhan’s design had no vulnerability, and his supplementaryapproach had no vulnerability either. From the physical layer to the decoding layer, the entire chain held up both theoretically and in simulation.
The reason he felt unsettled was: it was too smooth.
From signal cloning to SkyWalker—every step felt like someone had paved the road ahead of him. He fell into a pit, and there happened to be a door in the pit. He pushed open the door, and there happened to be a passage behind it. The passage happened to lead to an exit that could be used to escape.
He glanced at Farhan—the man had gotten up from the floor and was reviewing the test data, fingers flying across the keyboard, not noticing Lu Yuan’s expression. Lu Yuan did not voice his unease. Not because he did not want to, but because he did not know how to express it—he had no evidence, only an intuition, like a needle piercing some最敏感 nerve ending deep in his consciousness.
The thought came to him intuitively:
Milan Vojnović—the man who designed this system, who had planned every line of code before the first Starlink satellite ever launched—did he really not know about this vulnerability in the QKD channel?
Or was this vulnerability itself another door he had left in the system?
Someone like Milan—who could bury a backdoor for signal fingerprint cloning in Starlink’s authentication system, who could expose his existence to Farhan yet take no action—would such a person really overlook an obvious design gap like SkyWalker?
Lu Yuan stood in the shielded room, twenty meters of concrete and earth above his head, the lights of Shenzhen above that, and above that, a sky-net of a hundred and twenty thousand satellites. At some node in that net, perhaps there was a pair of eyes watching those five letters emerging from the tiny shielded room deep underground.
H E L L O.
Like an infant’s first cry.
Like a trap’s first snap.
Farhan turned off the simulator, packed up the cables, took off his headphones, and hung them around his neck. He turned to look at Lu Yuan, and on his face was an expression he rarely showed—something approaching warmth.
“If your daughter needs high-throughput communication—say, remote surgery—we can build a compute-sharing layer on top of SkyWalker. Let every node connected to SkyWalker contribute its idle computing resources. No need to fight for OrbitNet’s compute power—we’ll build our own.”
He said it calmly, like someone describing a plan he had been formulating for a long time. But Lu Yuan caught something in his eyes—not technical excitement, but something deeper, something symmetrical to the unease in his own chest.
Farhan was also suspicious.
But they both chose not to voice that suspicion.
Because regardless of whether Milan Vojnović was friend or foe, the road had already led to this point. The direction of retreat was sealed. The road ahead—whether leading to freedom or a trap—had to be walked regardless.
“Compute-sharing layer,” Lu Yuan repeated the phrase. “You want SkyWalker to become a distributed network?”
“Not that I want it—it must become that. With only the QKD channel’s bandwidth, SkyWalker cannot transmit large files or run AI inference. But if every terminal accessing SkyWalker—phones, tablets, routers, smart home devices—contributes a small fraction of their compute power, combined, they form a distributed supercomputer. Not a centralized behemoth like OrbitNet, but an alien machine pieced together from tens of thousands of tiny computing fragments.”
He paused.
“A machine that never asks what you’re computing. A machine that never refuses a request because your account tier is too low. A machine that—”
He searched for a word.
“—never bills.”
Lu Yuan looked at the cables and equipment in the shielded room. He remembered the high-definition butterfly video his daughter had seen at the hospital—images that had never loaded properly before. If that kind of smooth streaming were free for every child—no Platinum account required, no twenty thousand credit points per month, no father needing to steal a neighbor’s signal—
That would be another world.
He did not know if that world could be built. But he knew this world—the one with a hundred and twenty thousand satellites overhead, meticulously billing every bit—he was not willing to let it continue.
“Let’s go back,” he said. “My daughter will wake up soon.”
They walked out of the shielded room. The emergency lights at the end of the corridor cast long shadows on the concrete walls. Farhan walked in front, his steps quick, his back straight. Lu Yuan followed behind, the old injury in his left ankle still throbbing.
In his pocket, his phone screen lit up—a text message from an unknown number, only one word. Lu Yuan stopped in the corridor, read it by the dim light of the emergency lamp.
The message read:
「Hurry.」
No sender. No context. Just one word.
Lu Yuan stared at that word for two seconds, locked the screen, and quickened his pace to catch up with Farhan.
On the other side of the corridor, deep among those Faraday cage compartments, five-year-old Lu Zijing lay on her folding cot. Before her was an old graphics tablet, the screen showing an unfinished drawing: a butterfly with circuit-board-like patterns on its wings.
She added the other wing with the stylus, rested her chin on her hand, and looked at it for a while. It looked to her like something that could fly without air.
Like those stars passing overhead.
She did not know why she had that thought. She lowered her head and began drawing a second butterfly.
