Shulou(Shulou.com)06/01 Report--

No matter what I do, I always think that as long as my energy allows me, I will first serve my motherland. Selected works of Pavlov

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Pay attention, don't get lost!

  after the last stream cipher, let's take a look at the block cipher while the iron is hot.

  in some commonly used cryptographic systems, block ciphers still play an important role in maintaining system security. Like stream ciphers, there are many problems we need to pay attention to in the use of block ciphers.

What is the   block cipher? Grouping, as its name implies, is to encrypt plaintext messages into groups, that is, the encrypter can only process a set of data of a specific length at a time, and the "set of data" here is called a packet. We also call the number of bits of each packet as the packet length.

Thump, thump! Here we go!

After   read the explanation of the block cipher, you can see whether the cipher of the stream cipher and the cipher of the block cipher contain the explanation of memory element: for the block cipher, it ends the encryption process after processing a packet, so there is no need to record the progress of encryption through the internal state. On the contrary, for stream ciphers, it is a continuous encryption of a data stream, so the memory elements in it need to be encrypted to record the internal state of the cipher.

Block password:

  block cipher is the number sequence x0, x1, … Xi,... And divide it into groups x = (x0, x1, … , xn-1), each packet of length n has the key k = (K0, K1, … Under the control of kt-1), it is transformed into an equal-length output digital sequence y = (y0, y1, … , ym-1), whose encryption functions E: Vn × K → Vm,Vn and Vm are n-dimensional vector space and m-dimensional vector space respectively, and K is the key space.

  can see in the figure that enter a plaintext packet of length n, and output a ciphertext of length m after passing the cipher. But in general, we take mQun. If n > m, it shows that there is data compression in data encryption. If n

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