Chapter 255： Steganography

"Yeah, it's no use asking."

Xia Xu also realized this and was a little helpless.

Things went round and round and seemed to be back to square one.

Finding Pan Long's dad's blog was indeed a blessing, but the only clues now seem to be photos.

"Could it be some kind of steganography?"

After a moment of thinking again, He Qing suddenly made a suggestion.

Steganography, as the name suggests, is to hide the way of writing certain information, to hide certain information in another thing.

Different from encrypted communication and cryptography, steganography is not just to prevent third parties from knowing the content of the communication, but to go further and hide the fact of 'communication' itself.

"Wait, let me verify."

Meng Bochao was reminded and downloaded the picture on the blog page.

He first tried to use the easiest way to change the photo into a txt text format or a compressed file format such as rar to see if this format conversion could be used to hide some content and files.

After he didn't get the harvest, he tried more complicated methods one after another, and everyone quietly waited for his results.

"It does seem possible that lsb steganography is used, the probability of 0 values ​​in the least significant bits of the rgb value is too high."

After a while, Meng Bochao spoke up in high spirits.

"What's the meaning?"

Pan Long was confused by these convoluted professional terms, and he was most concerned about this matter and hurriedly asked.

"lsb is a form of steganography, short for least significant bit.

Usually a photo is composed of pixels, and the pixels are recorded with three values ​​​​of r, g, and b, as well as three channel colors of red, green, and blue, which are equivalent to the three primary colors, and any color can be composed of rgb values.

The rgb value is represented by a number of 0-255, and the number is stored in binary in the computer. The decimal system we commonly use is to add one to the number ten. Regular 0s and 1s are recorded for expression.

lsb steganography is to modify the least significant bit of the binary value, change the 0 of the least significant bit to 1, or change 1 to 0. After the binary value is changed, the rgb value will change, but it is only a small change. It's almost impossible to tell the difference..."

This is good, a large section of more convoluted concepts of popular science spit out from Meng Bochao's mouth, layer by layer, which can be called a Russian nesting doll.

"Stop, bully me for not understanding computers, right? Just tell the conclusion."

Yang Bowen stopped Meng Bochao with a big head.

"Well, to put it simply, the probability of occurrence of the least significant bits 0 and 1 in the pixel data of a normal photo is close to the same, but the probability of occurrence of 0 value in this photo is greatly exceeded, and it is likely that someone has made changes. ."

Meng Bochao stopped showing off angrily, and said simply: "This kind of change can't tell the difference with the naked eye, but the written information can be hidden by referring to specific rules, and these rules are also ready-made, and there are many jointly formulated character encoding tables in software development. , different numbers can represent different letters and even Chinese characters.”

"So you can decipher the hidden information inside?"

He Qing asked sharply.

"Theoretically, there are only those kinds of coding tables, and you can find out the rules by comparing them, but the problem is that I don't know which pixels are changed. I have tried it just now, not from the first and last pixels. Rules change."

Meng Bochao laughed awkwardly.

The current situation is that he knows that some text information is hidden in it, but he does not know that those are hidden information.

After all, pixel values ​​are also represented by numbers, and the result after comparing with the character encoding table is not necessarily the hidden information that was written.

To describe it simply, it is like a poem with a hidden head or a hidden tail. If you know that it is hidden, you can see it at a glance.

But if there are no rules hidden in it, it will be difficult to see, unless you figure out the rules or try to form words one by one.

"Isn't this a ready-made control group?"

Xia Xu picked up the physical photo on the briefcase and threw it on Meng Bochao's laptop keyboard.

Meng Bochao was probably a little complacent, and he glanced at Xia Xu speechlessly: "This is not photo data, and shooting or scanning this photo will produce light and dark differences, and the camera equipment will again cause random background noise, it is impossible to get the same. original digital images.”

"What if I could get a raw digital photo?"

Xia Xu raised his brows with a playful look on his face.

"Then I ate my notebook."

Meng Bochao patted his big belly.

"Haha, it's okay, I'll be a witness, how about opening another game? Do you want to make a bet?"

He Qing immediately booed.

Xia Xu said with a smile: "I don't mind, or I'll bet on your monthly salary. If you win, your salary will be doubled, and if I win, your monthly salary will be deducted."

"Boss, I support you personally, but you put me on the opposite side so directly..."

He Qing's face was distressed, and then instantly turned into a smile that couldn't be concealed: "I can't blame me for not supporting you."

"Of course, I don't blame you, anyone else wants to participate?"

Xia Xu looked at Yang Bowen and Pan Long playfully. As for Meng Bochao, he naturally participated by default.

"Hey, don't gamble, don't gamble, Lao Yang, I have a family, and I have to pay my salary, so I can't afford to gamble, but I still support and believe in you, boss."

Yang Bowen politely refused with a smirk.

As the first existence to follow Xia Xu, he knows his boss's ability, and he knows that he is well-informed and never does anything unsure.

"I'm not going to gamble..."

Pan Long also sneered and refused.

The reason for this is that, firstly, Xia Xu's image of being tall and dignified in the past two days is due to the fact that he is a little ashamed to say it - he has no money.

He is not an employee here, but he just inquired about it casually. The basic salary of Yang Bowen and these people starts at 20,000 if they don't work, how can he have so much money to bet.

"I, I believe in you too."

Although Tang Youxin did not participate, she also made a statement.

Well, it's so cute, as expected of my little white flower.

And Xia Xu naturally wouldn't let Xiao Baihua down, he reached out to pick up the photo on Meng Bochao's notebook again, and said with a smile: "I can't compare with you in terms of these professional skills, but I will restore this photo to the original digital negative. no way."

This is obviously followed by a 'but'.

"However, have you ever thought that Pan Long's father left steganographic messages in the pictures on the blog for covert communication, to be precise, to leave messages for specific people. In this case, it must be a There is a way to decipher it."

Xia Xu's remarks really opened up the minds of several people who were stuck in a dead end of thinking, but soon they realized that the essence of the problem had not changed, Meng Bochao said directly: "But boss, I also know that there is a way to decipher it, but the problem is What is the deciphering method? Where?"

"I said this just to tell you that this decoding method must exist, and it was left by Pan Long's father, or to be precise, the person who left the steganographic information."

Xia Xu smiled, raised the photo in his hand and said, "As for the decoding method, isn't it here?"

"At this?"

Everyone was completely stunned.

Because the problem still hasn't changed, they just can't get started with this photo.

After seven or eight laps together, it still returns to the origin? What about the Ouroboros?

Seeing this, Xia Xu could only helplessly continue to explain: "You can't just stare at this photo, this photo is actually just a reminder to let people know that this photo exists.

In fact, the key to decryption requires a different perspective, such as how did this photo come from? Surely you need a digital camera to shoot, right? Do you need to print for sure? "

"yes."

Yang Bowen on the side had an epiphany, and couldn't help but be amazed at the case: "The point is the source of the photo, you must have equipment to take this photo, and the age is so clear, those old cameras can't take pictures, they must have been taken with previous professional equipment. "

"That's right."

Xia Xu nodded with a chuckle: "So there should be original digital negatives in the camera, and since Pan Long's dad must have left a deciphering method, the camera must still be there, and the original negatives in the camera must also be preserved.

As for the place to keep it, it is also obvious. This photo that serves as a reminder is placed at Pan Long’s house, so only Pan Long and his family are most likely to get it. The camera or backup digital negative must be left there, or is the way to develop and print this photo. "

"Fuck, boss, you are amazing."

Everyone was suddenly enlightened, and then they all looked at Pan Long.

"I seem to have an old-fashioned digital camera at home, but I haven't used it. I didn't understand it when I was a child. When it got older, it would have been turned off and eaten ashes at the bottom of the cabinet."

Pan Long understood what they meant, and he looked a little excited as he recalled.

"Why are you waiting here, go back and get it."

Meng Bochao urged.

"I can't see that you are very kind, but don't forget, you can't default on your bet, and I won't pay you two's wages this month."

Xia Xu reminded with a smile.

Meng Bochao: "…"

"Boss, I was wrong, don't deduct my salary, I'm innocent, it was you who took the initiative to assign me to the enemy's camp, I am in the enemy's camp and my heart is Han~"

He Qing, who was reminded to realize this stubble, wanted to cry without tears in an instant.

"Hahaha, UU reading deserves it."

Yang Bowen immediately gloated.

Watching you lose money is more refreshing than making my own money.

"Boss lady, help me to say something nice~"

Compared with He Qing, Meng Bochao clearly realized who his savior was, and looked at Tang Youxin eagerly.

Unfortunately, classmate Xiao Tang glanced to the side with erratic eyes, pretending not to hear.

╭(╯^╰)╮Hum, I told you not to believe him, and now you still want to beg me, think beautifully.

I am also very stingy.

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