"John?"
John made a strange sound, something between a laugh and a sob. "I'm not going mad, am I? If you've thought it as well, then it can't be that I'm fucking losing it. Because really, Greg, I've spent the last few weeks convincing myself that Sherlock is actually alive."
Greg exhaled. "You've thought about this for weeks?" He felt a pang that John hadn't said anything about it -- but then, why should he have? It was mad even to think it, and until two minutes ago, Greg would have thought John had gone round the bend.
John reached over to the night stand for the towel he'd taken to keeping there and cleaned himself off. "If I'm to be completely honest, I've suspected it all along, but it wasn't until a few days ago that I was… well, certain isn't quite the right word. It's still possible that someone very clever is fucking with me."
"Like Moriarty?"
"Perhaps." John dropped the towel to the floor and stared up at the ceiling. "So tell me what you know."
Greg took a moment to dispose of the condom and then stretched out next to John on the bed. "The package you got, with the ball -- the handwriting wasn't Molly's. She's sent me thank you notes a few times, and she has this loopy girly writing. So I wondered if it was actually from her."
John nodded. "Go on."
"And then I saw her a few days ago and I asked her about it. She had no idea what I was talking about." Greg paused to look at him, but John kept his gaze on the ceiling, stonefaced. "So… God, this is going to make me sound like a fucking creeper, but bear with me. I googled 'rubber ball' to see if there was some hidden meaning, one of those jokes everyone knows about that I'd missed. And you know how Google does that thing where it finishes your search terms for you? One of the suggestions was 'trick pulse'."
John nodded. "Right."
"But I suppose someone could have been fucking with you by sending it to you. I mean, how likely is it, really?"
"I saw Sherlock with a ball exactly like that one in his hand the day he jumped."
Greg closed his eyes for a moment. "Okay. Okay, that's-- Wow, shit. So you think he used it for that?"
"Maybe. I honestly don't remember if I felt a pulse that day. It's all a blur now." It seemed as if John was about to say something more, but stopped himself. "What else?"
"You know what else. The web site. The faked death thread. The codes. That one commenter who sounds so fucking familiar."
John pressed his hands against his forehead. "You're forgetting about Mycroft."
"Right. He mentioned an analyst he was keeping a tight leash on, one who was angry that the security agent had killed the man he wanted to interrogate."
"An analyst who does interrogations?"
"That's what I said. Mycroft changed the subject. And he's terribly keen on moving forward with taking down Moriarty's criminal network."
"Which he wasn't in a hurry to act on before. But that's not actually what I meant." John dropped his hands and turned to look at Greg.
"Oh?"
John paused for a moment before continuing. "I saw Mycroft before it all happened. I went to yell at him for his carelessness, and he confessed that he'd essentially handed Moriarty everything he needed to ruin Sherlock. He barely seemed sorry about it at the time. I was… God, furious isn't even the word. I couldn't believe that Sherlock's own brother could be that stupid."
Greg nearly gasped as understanding dawned. "But he isn't that stupid, is he?"
"He's not stupid at all. He's perhaps even cleverer than Sherlock."
Greg stared back at John. "You think it was a set-up."
John nodded. "I think they planned it together, that they thought making it look like Sherlock was gone would provide their best chance to get Moriarty." He exhaled at that, apparently relieved finally to have said the words aloud. "So am I crazy?"
"I don't know. But if you are, then so am I." Greg stared up at the ceiling, his mind whirling as all the pieces fell into place. He could see it all now -- he just hoped it wasn't simply what he wanted to see.
John stared at him for a long moment. "What do we do now?"
"You seem to think there's something in the messages on the website. Do you think they're for you?"
"The newest one is different from the others, and it was posted right after I started the blog again. I can't help but think it's meant for me."
Greg pushed himself to sitting. "Well, let's take a look."
"Now?"
"Can you honestly tell me there's anything else you'd rather do?"
John exhaled. "No."
Five minutes later they had both cleaned up and dressed, and were huddled over the screen of the laptop.
"Most of these," John said, pointing at the coded messages on the screen as he scrolled down, "are coded in one of two ways. Many are simple substitutions of one letter for another. In order to decode, you have to figure out which letter stands for what. Sometimes they use numbers as well, but it works the same."
Greg nodded. "Classic spy novel stuff."
"The other way is based on a code system we learned about in a case we solved a year ago. I wrote about it on the blog."
"The one with the London A to Z book?" John looked up sharply and Greg shrugged. "I told you, we all read it." That and keeping up with the blog had been a prerequisite for being Sherlock's unofficial "handler" at Scotland Yard.
"Right, that one. Anyway, I reckoned that if it were really from Sherlock, he would have used a book he knew I owned, something I wouldn't have got rid of after he died. Or disappeared, whatever." He casually waved a hand in the air and Greg was struck by the fact that Sherlock being dead was no longer part of John's reality.
Greg swallowed. He had only just grown used to the idea of Sherlock being gone and all of this was making his head spin with questions and possibilities. Unlike John, he hadn't had weeks to adjust to the idea. He pushed all of it aside for the moment and forced himself to focus on the task at hand.
"So you tried all the books you have?"
John nodded. "I got nowhere. So then I figured it must be a substitution cipher, and spent the last two days trying to work it out." He pressed a hand over his forehead. "I must be missing something. Or I'm being fucked with, I don't know."
Greg frowned at the screen. "If it were really from him, he'd want you to work it out. He wouldn't have made it hard for you."
John snorted. "This is Sherlock we're talking about. He'd enjoy watching me struggle with it."
"No, I don't think so. He would have wanted only you to work it out. He even said so, didn't he? I only expect one or two of you to be able to work it out. He would have made it something easy for you but hard for everyone else." He looked away from the screen for a moment -- he was likely in the latter category.
"So what, he would have used some really rare book, something he knows only I would have?" John held his hands out to the side and then dropped them again, clearly frustrated. "I've gone through everything I've got, even books I wasn't sure he knew I had, like weird porn under my bed. Nothing worked."
"You keep weird porn under your bed?"
"Where else do you keep weird porn?" John pointed to the screen. "But this doesn't match up with anything, and I don't know what else to do."
They sat in silence for along moment, both of them staring at the laptop screen.
"I'm hungry," Greg said at last. "Why don't we go get something to eat, get our minds off it a bit, and then come back and work on it all night."
"What, beer and pizza?" John half-smiled. "Okay, yeah. Why not?"
There was a pizza restaurant a ten-minute walk away, a hole-in-the-wall spot with half a dozen red-checkered tables and a large selection of draught beer. John had never been there, to Greg's surprise, and was happy to let Greg order for them both. John didn't talk much while they waited for their food; he listened to Greg rant about how hard it was to find authentic Italian food in London and nodded every so often, but it was clear he wasn't really listening.
The pizza arrived at last and they both dug in. Silence stretched between them for a solid minute, and Greg finally couldn't bear it any longer.
"So if he is alive, why'd he do it? Why did he have to fake his own death like that?"
John traced a fingertip around the rim of his own glass and looked up. "You mean without telling anyone?" The not even me was implied, but Greg heard it all the same.
"We're assuming Mycroft is in on it, right?" Greg clenched his jaw. "It would at least explain why he left the funeral so early, as if it was such a horrible inconvenience for him."
John pressed his lips together and looked thoughtful for a moment. "I've thought about it a lot the last couple of weeks, and I've no idea why he didn't think he could tell me. Perhaps he thought he was protecting me somehow, that he needed to do this alone."
"Do what alone?"
John glanced around the small restaurant and dropped his voice. "Finish off Moriarty. I suppose he thought I wouldn't be able to help, that I'd just get in the way." He tried to smile, but the tension underneath it was clear.
"You're angry at him. I don't blame you."
John's face fell and he looked down at the half-eaten slice of pizza on his plate. "I'm not angry; I'm fucking furious. Why would he put me through all of that? He knows what I… how I…"
"This is Sherlock we're talking about, remember? He has fucked up ways of showing he cares."
"Don't I know it."
Greg watched him for a moment, tracing the paths John's whirling emotions were leaving on his face. "Maybe it wasn't meant to happen the way it did. Maybe it was a back-up plan, or something, and he didn't have time to tell you."
"He could have left a fucking note explaining it all." John's gaze was firmly fixed on the table.
"He did, didn't he? He sent you the ball. He knew you'd work it out."
John looked up at that and his expression softened a bit. "He could disguise his handwriting, did you know? He had studied all these different types of writing and how to analyze them and he could write like a child or a teenage girl or a pensioner, or whatever. But he always did a few letters the same no matter what, and it drove him mad. He once practiced for days on end, but when he wrote quickly, he couldn't get it right."
"So the writing on the package was his, then?"
"Everything but the k and t was off. And he'd have known I would notice. Well, he'd have hoped, anyway."
"You see? He wanted you to work it out."
"So why can't I work this fucking code out, then?" John pressed his fingers against his temples as if his head hurt. "There must be something completely obvious that I'm missing."
Greg took another sip of his beer and sighed. "Maybe it's not meant to be decoded. Maybe the message is in plain sight."
John laughed and shook his head. "That's nearly fucked up enough to--" He paused and looked up at Greg. "Say that again."
Greg blinked at him. "Erm… maybe the message is hiding in plain sight."
John's face grew oddly pale. "Oh, God… That's got to be it. That's exactly like--" He stood, pushing his chair back so quickly it made a loud scraping sound on the floor. "I've got to go, I--"
"Go, I'll get the bill."
John nodded and nearly sprinted out the door. Greg turned back to the half-eaten pizza, his appetite long gone. He signaled the server, who nodded in immediate understanding -- it wasn't the first time he'd had to leave this place halfway through a meal, after all. He finished the beer while he waited (no need to let a perfectly good pint go to waste) and let the events of the last hour replay in his mind. He'd done his best to remain skeptical, to be neutral and objective about the evidence they'd discussed, but John's growing excitement was contagious. If Sherlock were actually alive, if this entire thing had been a secret plot to finish Moriarty once and for all, then the fact that Sherlock had willingly sacrificed his reputation and his livelihood to do it was nothing short of stunning for a man who claimed to be a sociopath. Greg wasn't sure John would see it that way, but if it were true, it would change everything. He had to be ready, to make sure the Metropolitan Police were ready.
Whether he was ready was another question altogether.
Fifteen minutes later he returned to the flat, pizza box in hand, to find John sitting on the sofa, staring frantically at the computer screen.
"Any luck?"
John shook his head. "Here, take another look. Do you see anything in there that makes sense?"
Greg sat next to him and took the laptop.
Message: ghhldsjftPK188417fnnd0801subl
Hint: dhkxp23753g53
"There's a backwards 'bus'."
"Yes, I thought of that, followed by some numbers and nonsense letters, perhaps a bus number or route or time. I searched but couldn't find anything that matched. Not in London, anyway."
Greg stared at the screen for a full minute, but there was nothing else that really stood out. He frowned and sat back against the cushions of the sofa. "Whoever this RandomCrazyAnon guy is, he's got Sherlock's number, that's for certain."
"RandomStupidAnon," John corrected.
"And what's up with the name anyway? Sherlock would never call himself stupid, not even ironically. He'd call everyone else stupid, but--"
"Shit!" John hissed and yanked the laptop away from him. "Fucking buggering hell, I… Oh my God, that's it." An expression somewhere between glee and astonishment spread over his face and he waved a hand at Greg. "Quick, paper, pencil!"
Greg scrambled for the pad and pencil and handed them to him. "What?"
"Oh my God, there it is. It's… Oh, God, how did I not see this before?"
"See what?"
"RandomStupidAnon -- RSA." He scribbled something Greg couldn't quite make out on the pad of paper. "We had this case about seven or eight months ago, and it all ended up being classified, so I never blogged about it. One of the things that came up during the case was a coding system called RSA. It's only been declassified in the last decade or so, but… well, that part's not important." He paused to stare at the paper.
"Okay, secret code system," Greg prompted after a moment.
"Right. It's a public key system, meaning that there are two different codes, one that's given out publicly and one that's kept private. The public key is used to encode messages and anyone can do that, but you need the private key to decode, and that's nearly impossible to break in practice."
"Wait, so… so he's using a code that's impossible to break to send you a message?" He had to admit it sounded like something Sherlock would do.
"Impossible to break, but completely easy to use if you have the private key. And here--" He circled at a string of letters in the hint. "--he's told us exactly how to get the private key."
Greg stared at the paper; John had circled dhkx. He shrugged and looked up at John, whose eyes were ablaze with excitement now.
"Diffie-Hellman Key Exchange. He made me learn how to do it during that case, and I was annoyed as fuck because it involved some fairly complicated maths. And of course he never said, 'Hey, we might need this to communicate in secret one day' or I might've paid closer attention. But I'm sure I can look it up." He opened another tab and googled, then spent a few minutes staring at a Wikipedia page with more mathematical symbols on it than Greg felt comfortable with. He sat for a moment and felt utterly useless.
"I'll put the kettle on," he said at last, and stood and crossed to the kitchen. His mind was whirling now, and not just from the fact that all of this made far more sense to John than it did to him. If John was right, it probably meant Sherlock was really out there, trying to contact him. But why did he have to do it in secret? Why go to such lengths when he could send an email or pick up a fucking phone?
The kettle whistled and he poured two cups. If Sherlock were truly alive, Greg wasn't sure whether he'd first want to hug him or punch him.
He returned to the sofa with two cups of tea, both of which he ended up holding because John was typing numbers into some sort of online calculator. "Do I even want to know what you're doing?"
"The key exchange works like this," John said, picking up the pad of paper. "Two people want to exchange a secret, but they have to do it in a public place, like a web forum, where everyone watching will be able to eavesdrop. So they publicly agree on two numbers that they'll use, which he's already done here, see?" He circled two sets of characters in the message hint: p23753 and g53 and paused to grin at the page. "He's even using the same variables as the ones on the Wiki page. He knew I'd have to look it up."
Greg decided it would be best if he pretended he was following all of this. "Okay."
"So those are publicly known. What happens next is that he and I each choose a number that we'll keep secret. He's chosen one already, and I'll choose…" He paused and looked thoughtful for a moment. "I think it has to be a prime number."
"Like seven?
"Larger than that. Is 61 prime?"
"Ermm..." Greg frowned. Not divisible by three or five or--
"Wait, I can google that." John typed Is 61 prime? into the search bar and a split second later got half a dozen results confirming it was. "Okay, so now--" He flipped back over to the Wikipedia page. "Right, now we each have a number, and we do this computation." He wrote on the notepad.
5361 (mod 23753)
"Do you actually know what all of that means?"
"Sort of. Happily, there are online calculators that can do the arithmetic for us. Let's see…" He clicked on another tab and typed numbers into a web form. "I get 9550, and we'll send that back to him."
John tabbed back over to the discussion forum and clicked the Leave comment button. "Oh God, look, Temlar113. Sherlock's last login and password are still here. He must have saved it on my machine before he…" John trailed off and pressed enter.
Greg turned to look at him. "If it's really him, he'll know this is you. No one else would have that login information. You said no one on the site ever suspected it was him."
John nodded, his jaw clenched. Greg watched as he typed 9550 into the comment form and pressed submit.
"What now?"
"Now we wait for him to send us his result." John frowned and looked at the message again. After a moment he grinned at the paper and circled some characters in the message. "Look, he's already told us what the public key is. PK is 188417."
"So when he sends his result, you'll have the private key?"
"Not quite, but I'll just have to do another computation to get it." He set the laptop on the sofa table and leaned back against the sofa cushions. He took a deep breath, his brow furrowed, and released it slowly, as if trying to calm himself. John was always so steady, so sure, and this was the closest to the surface Greg had ever seen his emotions rising.
"Are you all right?" Greg asked after a moment.
John turned to look at him. "Yes. Maybe. I'm not sure, honestly. Am I just seeing what I want to see? And if it's really him…" He paused for a moment and looked up at the ceiling.
"It raises a lot of questions, I know."
"I get Mycroft, but… why did he trust Molly and not me?"
"Shit, I hadn't even thought of that." Greg closed his eyes. He'd just seen her, and all that time she'd known, had been in on the secret.
"Goddammit. Why did I fall in love with such an immense prick?"
Greg looked over at him: John's earlier excitement had abated and morphed into something else altogether, something complex and tense. He felt a sudden compulsion to distract him from it, to pull him back from the edge, to keep him grounded in the reality of here and now. He bumped his knee against John's. "It's really that big, is it?"
John's brow furrowed for a full second before he turned to look at Greg. He finally shook his head and laughed, and pressed back with his own knee. "Well, no, not really. Average, I suppose?"
John smiled and there it was again, that rush of emotion that Greg had been so carefully avoiding dwelling on -- something that went well beyond attraction, something that was now mingled with hope and fear about what might be coming next and what it would mean for the two of them. John's expression was one of such fondness, though, that Greg couldn't help leaning forward and pressing a kiss against his lips. John kissed him back without hesitation. He slid one hand around Greg's shoulders and moved closer to him as he deepened the kiss, and Greg tried very hard not to think about the fact that John could kiss him like this seconds after saying he was in love with someone else.
John pulled back and pressed his forehead against Greg's. "I'm sorry I've been such an arse these last few days."
Greg smiled. "I wasn't all that cross, but if this is how you plan to apologize, I'll have to find more shit to get pissed off about."
John laughed. "Don't expect me to make it easy for you."
Greg stroked John's cheek with his fingertips. "You're amazing."
They stared at each other for a long moment. Greg felt his cheeks warm and he looked away. He hadn't meant to say it out loud.
A pinging sound came from the computer and they both turned to look. John picked up the laptop and stared at the screen. RandomStupidAnon had replied to his comment with the number 15740.
"Oh, God." John looked back up at Greg, and he felt an odd sort of anxiety shoot through him. They were going to know one way or the other very soon.
John plucked the notepad from where it had fallen on the floor and wrote the new result under the old one. "So now we take this number and do the same thing, raise it to the sixty-first power mod that other big number, what was it? Ah, yes." He clicked over to the tab with the online calculator and typed the numbers in, then pressed submit.
Greg leaned forward to see the result: 20333. "Okay, what now?"
"That's it," John said. "That's the private key."
"So we can send a message now?"
"Yes, I think so. We can send him a message by using the public key to encode and the private key to decode, and he can do the same. It should be completely confidential." John tabbed back over to the RSA Wiki page and then frowned. "Shit, no. There's one more piece of information we need." He clicked on the discussion forum tab again and scrolled up the thread to look at the original message. "I don't think we have it yet. We have to wait for him to give it to us."
As if in response, the computer pinged again and a new message from RandomStupidAnon appeared at the bottom of the thread.
Very good, Temlar113. If you want to try another, check the forum.
"Of course," John said as he scrolled to the top and clicked the link for the main forum. "He can't put everything in one thread or someone else might be able to work out what we're doing. The numbers aren't actually large enough for it to be terribly secure, I think."
Sure enough, RandomStupidAnon had made a new post to the main codebreaking forum.
RandomStupidAnon
Posts: 386
30 July 23:34 Since most of you had no luck with the last coded message, here's another:
Message: 21398, 372271, 38466, 209127, 159172, 355235, 39971, 98989
Hint: ghjstn410549dhl
Good luck!
"And he's given us the n value we needed, look." John pointed at the hint on the screen and then reached for the notepad again. He wrote down the message and then n = 410549. He took a deep breath and clicked over to the online calculator tab he'd just used. "Here we go, then."
Greg sat back and watched him enter numbers in the app and get new numbers, which he wrote down on the notepad and then stared at with a frown. Greg leaned over his shoulder to take a look.
214, 2011, 301, 403, 13, 604, 1714, 2018
John pursed his lips. "So now the question is, did he just do a simple alpha-numeric substitution?"
"Like A is one, B is two, that sort of thing?"
"Yeah, except some of these numbers have two digits and some have four. I'm thinking each of the numbers represents two letters in the message, which means this one--" He pointed at the number 13. "--should actually be zero-zero-one-three. So that probably means he's using A is zero, B is one, and so on. Let me try it." John quickly wrote down the alphabet and then numbered each letter starting from zero. "So two is C, fourteen is O, twenty is U, yeah, I think this is correct."
Greg sat back against the sofa and waited, a knot of anxiety forming in his stomach. This was it, after all. If RandomStupidAnon was really Sherlock, he would have chosen his first message carefully. It should be obvious it was really him. At least, Greg hoped it would be.
After half a minute more, John dropped the pencil and the notepad and put his hands over his face. Greg sat forward again.
"John?"
John dropped his hands and stared straight ahead. His face was pale and his forehead furrowed, and his eyes were bright.
Greg picked up the notepad from the floor. "Could be dangerous."
John exhaled, a long slow breath blown steadily through his lips before rummaging through his pocket for his phone and tapping at the screen. He scrolled for several long seconds and then handed the phone to Greg.
Text from: Sherlock Holmes
30 January 2010 20:43
Could be dangerous. SH.
"That was one of the first texts he ever sent me, right after we met. He'd already worked out who I was and what I needed, well before I ever did."
Greg swallowed, hard. Jesus. "And you've never mentioned that to anyone?"
"It's something only he would know." John shook his head. "Unless, of course, someone found his phone and went back through his texts to find something specifically to trick me into thinking…" He winced and looked away.
Greg gritted his teeth. John had a point. They needed something more to be certain. "All right, so you should ask him a question. Something only he would know the answer to."
"Right." John pressed his fingertips into his temples. He picked up the pad and started writing.
Greg left him to it and went to take a shower. His mind wandered in the steam, from a jolt of excitement at the idea of seeing Sherlock again to a stab of fear of what it would mean if this wasn't real, the cruelty of John being given this sort of hope and then having it taken away all over again. People didn't get second chances like this very often. What would John do with his? And hell, what would Greg himself do?
He changed into pyjamas and settled next to John on the sofa to see him still writing on the notepad.
"Still working on the message?"
John shook his head. "Already sent it and got a response. Decoding now."
"Bloody hell," Greg muttered. He hated this sort of suspense.
John sat back after a moment and nodded.
"What?" Greg looked at the notepad, where John had just written friends protect people.
"I asked him what was the last thing I said to him in person." John looked up at him with an oddly tense smile. "It's him, Greg. I know it's him."
Greg sank back into the sofa, his mind reeling. "Fuck me."
John scrubbed a hand over his face. "Yeah. So what the hell do we do now?"
Greg shook his head. "I've no idea."
*****