Brief description of the group password Working Mode

This article will introduce the working mode of group passwords in symmetric encryption-RT.

Working Mode:
In fact, it was very dull. Today, I suddenly understood what this model means?
The so-called mode is the method, that is, the encryption method. Since it is symmetric encryption, the decryption method is also included. In the group password theory, a group is encrypted to generate a corresponding group ciphertext. As for how to encrypt the Group, there is no restriction on the mode, which corresponds to "How to encrypt" here ", from A.M. To a.m., we can choose from A to B, or from A to C to B. This is also often the case in the software structure. The upper layer may not need to know how the bottom layer works, or the lower layer does not know the upper layer, so it is better to do their own internal tasks. I don't know whether the designer proposed this concept out of such consideration. As the philosophy says: separation of mechanisms and policies is true. Why can't I figure it out today! It is possible to encryptAlgorithm(Cipher Algorithm) And mode (Mode. The encryption algorithm is used in the mode. Common grouping encryption algorithms include des, 3DES, and AES. They all have matching modes. For details, refer to [1].

Mode classification:
1) ECB (Electronic codebook)
A. All groups use the same key, and the same plaintext produces the same ciphertext. Therefore, it is the simplest grouping mode.

B. encrypt and decrypt functions.

2) CBC (Cipher Block Chaining)
A. all groups use the same key. However, the input of the encryption algorithm is the difference between the plaintext of the current group and the previous ciphertext (IV is required for the first time ), this overcomes the defect that the ECB uses the same plain text to produce the same ciphertext.

B. encrypt and decrypt functions.

3) CFB (Cipher Feedback)
A. Each group in this mode can use different keys, which becomes a streaming password, so the group length can be not all equal;

B. IV is a shift register, which must be used for each encryption/decryption;

C. Similar to the chain structure of CBC;

D. encryption function encryption,EncryptionFunction decryption.

4) ofB (output feedback)
A. Similar to CFB, the output of the cryptographic algorithm is used as the input of the next group;
5) CTR

A. Use a unique counter. The output (Stream key) obtained by the cryptographic algorithm is different from the plaintext or the ciphertext is obtained. The CTR has the similar nature of CFB;

B. Unlike the link mode, this mode can be executed in parallel, which is highly efficient;

C. encryption function encryption,EncryptionFunction decryption.

--- The above five modes are the group password mode recommended by NIST. For details, refer to [1] ---

6) cts

7) lrw

A. The name is a collection of three authors;
B. Two keys are required. For details about the process, see [3.
8) PCBC

9) XTs

 

References:

[1]. NIST Special Publication 800-38a 2001 Edition

Http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation.

[3]. Draft Proposal for tweakable narrow-Block Encryption

--- Content needs to be supplemented slowly ---