I Am Not A Mage Lord

　　 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 between cryptography in the Sismana rune and even the spell model.

　　 "Don't be nervous. Cryptography is a non-public subject at 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 Lin Qi 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 that Lynch was facing the blackboard with his back to the crowd, lingering, 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, 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 be encrypted into bcd, the "replacement method" in classical cryptography.

　　 If it is replaced with 1, 2, 3, 4...

　　 Then abc can be encrypted into 123, the "substitution method" in classical cryptography.

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

　　 The prototype of runes in "Fu Wenxue" is "plain text", and the "cipher text" obtained through "encryption technology" has initially got rid of the characteristics 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 incomplete?"

　　 In fact, Lynch used the "solid model" of the Palace of Memory to record the specific runes 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 that he was remembered on the spot, and that encryption was useless, and it was 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 mages use more than a dozen encrypted runes as rune archives."

　　 "The three are the mystery of the encryption algorithm and the key. The more people who know it and the more users, the easier it is to reject this encryption technology."

　　 "Therefore, cryptography is not publicly disseminated at Bluestar, and even many secret sects have a set of encryption algorithms for self-communication. That's why."

　　 At these words, Lin Qi opened his mouth slightly, "Then mentor, isn't it the best way for the mages to create a set of encryption methods for mystery?"

The female mage was taken aback for a moment, and she laughed out quickly, "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".

　　 As 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 to cde.

　　 "If it doesn't work, come down, classmate." Looking at Lynch on the podium, someone suddenly sneered.

　　 "Hey, the boss just thinks 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 a mage apprentice is this?" The descendants of the mage family, who was refused to join the team by Lynch, ridiculed him.

　　 "You can do it, you can go up." Chen Shikun listened to the sound from behind, turning around and mocking.

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

　　 Watching the quarrels 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 slapped their spirits and calmed down.

　　 Lynch couldn't help taking a deep breath. Is this a shaper 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 is already a little wondering, how cheeky is the leader of this year?

　　 Lynch smiled slowly, "Okay, I will write now."

　　 As he spoke, he took a long breath, his eyes sharpened, and he seemed to be able to cut gold and jade.

　　 Realizing that the more mysterious the "encryption technology", the more it can suppress the characteristics of runes that repel memory. Naturally, Lynch is reluctant to give out the cryptographic crystallization of 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, SM2, etc., which are used for Ukey identity verification in the bank.

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

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

　　 The MD5 algorithm is a "one-way hashing" technology in addition to the encryption and decryption algorithms. In essence, it inputs a piece of information of any length, and then outputs a fixed 128-bit character.

　　 This algorithm cannot parse out plain text, but it can be used to confirm whether the "information" is complete and whether it has been tampered with.

　　 is equivalent to "information" ID card.

　　 Such as the simplest digit statistics, "abc" is plaintext as "3", and "efgg" plaintext 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.

　　 So 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 video content. When it finds that there is a problem with the A film, there is no need to look up the name ~www.wuxiaspot.com~ Just delete all the videos saved by all users with the same MD5 value!

　　 Therefore, LSPs often find that they have been struggling to save and even deliberately change the name of the film, it is still difficult to escape the poison!

　　 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 "one-way hashing" technology to check "data completeness"!

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

　　 and the MD5 value of "Xiuqi" is 2a555bd60795efef39394b024350639b.

　　 And this checking algorithm does not involve rune encryption and decryption.

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

　　In an instant, Lynch began to write like a dragon with his chalk pen.

　　 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 like this, 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 Lynch, according to the "Rune Confidentiality Act" regulations, all rune algorithms that are judged to have a value of B or above cannot be disclosed in public."

　　 said with a smile on her mouth, "Come to my office in the afternoon."