I'm Really Not Faye

Chapter 48 Network Disk Video Nemesis MD5 Algorithm

Cryptography is essentially a discipline that studies how to secretly transmit messages.

It is not an exaggeration to say that it is the “learning of communication in the enemy’s environment.” After being closely integrated with mathematics, computer science, and informatics, it has been developed by leaps and bounds.

When Lynch studied Bitcoin in his previous life, he also specialized in cryptography for the blockchain. At the moment, he has many cryptographic models in his mind.

However, holding the chalk at the moment, what he is thinking about is the correspondence of cryptography in the rune of Sismana and even the spell model.

“Don’t worry, cryptography is a non-public subject in Bluestar. It is not surprising that you have not been exposed to it before. If you find it difficult, you can design a simple encryption algorithm and we will discuss it in class.”

The female mage An Qi looked at Lynch hesitantly, knowing that these proud children in the front row were arrogant and couldn’t bear to hit too much, she still gave a step down.

The apprentice below saw Lynch facing the blackboard with his back to the crowd, lingering, and couldn’t help but feel a little anxious.

“Isn’t the encryption algorithm difficult?” Roommate Chen Shikun asked his neighbors curiously.

“It’s not difficult as you can think of it, but how can Lynch use this kind of general merchandise? This is no more compelling.” Apprentice Liu Kai sighed.

And Lynch, who was holding the chalk, knew this too.

For example, the alphabets a, b, c, d…y, z are shifted by one bit, respectively, designated as b, c, d, e…z, a.

abc can then be encrypted as bcd, the “replacement method” in classical ciphers.

If it is replaced with 1, 2, 3, 4…

Then abc can be encrypted into 123, the “substitution method” in classical ciphers.

As long as the “key” of the permutation table is known, the “ciphertext” can be decoded into “plaintext”.

The prototype of rune in “Rune Studies” is “plaintext”. The “ciphertext” obtained through “encryption technology” has initially got rid of the characteristic of “memory exclusion”.

In an instant, Lynch turned his head and looked at the female mage An Qi keenly.

“Lecturer, I would like to ask. That day I used a function to memorize the ‘Oath rune’, which is essentially a kind of encryption. Why is the latter function still incompletely memorized?”

In fact, Lynch used the “solid model” of the Palace of Memory to record the specific rune on the spot. This statement was simply a statement of the suspicion that Master Mofeng had on him.

It’s not easy for him to say on the spot that he was memorized, that encryption is useless, and it’s too slapped.

The female mage Rikami smiled, “This is the meaning of this course.”

“Memory rejection mainly depends on several points, one is to restore similarity, like the replacement of abc in the textbook with bce, the similarity is too high. Encrypted to 123 is more resistant.”

“The two are the complexity of the encryption algorithm. The more complex the process and the more complicated the calculation, the better the effect. This is also the method adopted by many mages. They even awkwardly re-encrypt the ciphertext directly to form multiple encryptions.”

“But the shortcomings are also obvious. If you really want to use it, the decryption process alone will be extremely long and difficult to use for instant casting. The wizards use more than a dozen re-encrypted runes as rune archives.”

“The three are the mysterious nature of encryption algorithms and keys. The more people and users they know, the easier this encryption technology will be rejected.”

“Therefore, cryptography is not publicly disseminated in Bluestar, and even many secret sects have a set of encryption algorithms for self-communication. That’s why.”

Lynch opened his mouth slightly when he heard these words, “Then mentor, isn’t it the best way for the mages to create a set of encryption methods for mysteriousness?”

The female mage was taken aback for a moment, and she quickly laughed, “It is true, classmate Lynch. But I can only remind you that most of the algorithms you can think of have been used by the mage, even if you change it slightly. , Will also be considered similar. You can only bet that there are fewer people using it, or you can change the key yourself.”

Lynch nodded clearly.

The encryption process is essentially divided into two types: “encryption algorithm” and “key”.

For example, in the classical password replacement method, replacing the letters abc with other letters is an “algorithmic” process.

But “shift one bit” is the key “1”.

So the second person can continue to use the “replacement method”, but the agreement is that the “key” is 2, which means that two bits are moved, so that abc will be encrypted as cde.

“If it doesn’t work, come down, classmate.” Looking at Lynch on the podium, someone suddenly sneered.

“Hey, the boss just thinks about it for a while, what do you know?” The one who met Lynch and said hello spoke out to defend him.

“He went to bed at 12 o’clock last night, what kind of mage apprentice is this?” The descendants of the mage family, who was refused to join the team by Lynch, ridiculed.

“You go, you go.” Chen Shikun listened to the sound from behind, turning his head and mockingly said.

“I commented on whether the food is good or not, and I can cook without it.” Another apprentice directly pushed back.

Watching the quarreling waves below gradually increased, it also made the female mage An Qi a little annoyed. She glanced at the audience with cold eyes, and instantly the whole space seemed to drop a few degrees in temperature.

Many apprentices immediately shook their spirits and calmed down.

Lynch couldn’t help taking a deep breath. Is this a sculptor or a conjurer?

He knows that some specialized wizards can simply reproduce the effects of simple spells. This cooling is obviously the opponent’s method.

“If it doesn’t work, or if you think you haven’t figured it out yet, you can think about it before you come up.” The female mage An Qi suppressed her inner temper and comforted Lin Qi.

At this moment, she was already a little wondering, how cheeky is the leader of this session?

Lynch smiled slowly, “Okay, I will write now.”

When he said that, he took a long breath, his eyes sharpened, and he seemed to be able to cut the gold and break the jade.

Realizing that the more mysterious the “encryption technology”, the more able to suppress rune’s characteristic of repelling memory, Lynch is naturally reluctant to reveal the cupped hands of cryptography from the previous earth.

Encryption and decryption technology is divided according to whether the encryption “key” and decryption “key” are the same.

The same key is a symmetric algorithm, the stream type is RC4, and the packet type is DES, AES, IDEA, SM4, etc., which are used for user password transmission and storage in the bank.

Different keys are asymmetric algorithms, such as RSA, DSA, ECC, SM2, etc., and are used for Ukey identity verification in the bank.

From these initial points of view, each of them is Lynch’s wealth!

However, Lynch suddenly remembered an algorithm that countless LSPs hated-MD5 algorithm.

The MD5 algorithm is a “one-way hash” technology in addition to the encryption and decryption algorithms. In essence, it inputs a piece of information of arbitrarily long and then outputs a fixed 128-bit character.

This algorithm cannot parse the plaintext, but it can be used to confirm whether the “information” is complete and whether it has been tampered with.

An ID card equivalent to “information”.

For example, the simplest digit statistics, “abc” is plain text as “3”, and “efgg” plain text is “4”. By comparing the difference between 3 and 4, we can find that the original “abc” has been tampered with.

The “MD5” algorithm is a highly referential information digest algorithm.

Therefore, some of the “movies” that Lynch saved in the network disk in the previous life will have a 128-bit MD5 value.

The network disk party does not need to check the specific movie content. When it finds that there is a problem with the A movie, there is no need to look up the name, just delete all the movies saved by the user with the same MD5 value!

Therefore, LSPs often find that they have been struggling to save and even deliberately changed the name of the film, it is still inevitable!

Even when the software is released, the corresponding MD5 value will be disclosed. Once a hacker modifies the software and implants a virus, the MD5 value verified in this way will not correspond.

This is the key role of the “one-way hash” technology to check “data completeness”!

For example, the MD5 value of “Lynch” is 997952855bddc4b742d5df415886d1a6.

The MD5 value of “Xuqi” is 2a555bd60795efef39394b024350639b.

Moreover, the algorithm of this check does not involve rune encryption and decryption.

So Lynch didn’t worry about any loss in spreading.

In an instant, Lynch’s chalk pen began to write like a dragon.

The female lecturer looked at the increasingly complicated algorithm model on the blackboard, her mouth opened slightly.

However, her eyes gradually brightened compared to the gradually confused apprentices in the audience.

“You are not an encryption algorithm, but a digest algorithm?”

“And if you write this way, it will correspond to countless possible plaintexts, used as a comparison to prevent tampering?”

“Boom!”

Suddenly, the female mage An Qi directly pressed Lynch’s hand, making him feel a chill.

The female mage took a deep breath, her eyes gradually becoming deeper.

“Student Lin Qi, according to the “Rune Confidentiality Law” regulations, all rune algorithms that are judged to have a value of B or above cannot be disclosed in public.”

She said with a smile at the corner of her mouth, “Come to my office in the afternoon.”