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Cryptography provides the following services:

Encrypted Encryption

Hash Hash functions

Message authentication code Message Authentication codes (MAC)

Digital signature Digital Signatures

The goals of cryptography are:

Confidentiality Confidentiality

Data integrity Data Integrity

Certified Authentication

Non-repudiation Non-repudiation

The following table shows what the various services can achieve.

Encrypted hash message authentication code digital signature confidentiality √

Data integrity

Sometimes √√ authentication

√√ non-repudiation

Sometimes √

Confidentiality discussion

When building a cryptosystem, we need to consider the possible exposure.

There are different methods of classification from different angles.

According to the action, we divide * * into passive (passive) and active (active).

Passive *

Access information without authorization (pay attention to initiative, pay attention to access, not change). For example, intercepting and eavesdropping are passive. Passive * * will not affect the original information, nor will it disturb the original connection.

Active * *

Unlike the passive, this kind of information will change the original information in some way.

According to the methodology (Methodolgy) of * *, we can divide * * into the following categories:

Pure ciphertext * (Cipertext-only Attack-COA)

* users can get the corresponding plaintext only by visiting the secret text collection. Occasionally, those who have sex can also get the key.

Known plaintext * (Known Plaintext Attack-KPA)

The person who knows part of the secret text knows the clear text, and according to this one, he deciphers the other secret text.

Select plaintext * (Chosen Plaintext Attack-CPA)

* the plaintext / ciphertext pair of his choice is mastered and the key is analyzed. RSA is easy to find.

Dictionary * * (Dictionary Attack)

* people set up dictionaries of plaintext and corresponding ciphertext, and query them in the dictionary when they encounter ciphertext. There are many variants of this kind.

Violence (Brute Force Attack-BFA)

After knowing the algorithm and ciphertext, the user tries the possibility of various keys until it is cracked.

Birthday * (Birthday Attack)

Used for hash cracking, is a variant of brute force cracking.

Middleman (Man in Middle Attack-MIM)

Can be used for the public key. A communicates with B, A requests the public key from B, and the * sends his own public key to An and gets the public key of B. Then maintain the communication in the middle to get the information.

Bypass * * (Side Channel Attack-SCA)

It is used to obtain the physical implementation weakness of the key system to carry out *.

Timing * (Timing Attack)

A kind of bypass. Try to crack the algorithm by analyzing the execution time of the algorithm.

Power consumption Analysis * * (Power Analysis Attack)

* by obtaining power consumption data.

Fault Analysis * * (Fault analysis Attack)

Carry out * by analyzing the fault.

Modern encryption technology

Symmetric encryption technology can be divided into block encryption and stream encryption.

Block encryption (Block Ciper). The fixed block data is encrypted each time. The deficiency should be Padding.

These technologies are: DES (Digital Encryption Standard), Triple DES, AES (Advanced Encryption Standard), IDEA, Twofish, Serpent and so on.

DES is developed based on Feistel Block Ciper model.

Other models include Electronic Block Ciper Mode, Ciper Block Chaining Mode, Ciper Feedback Mode, Output Feedback Mode, and Counter Mode.

There are three schemes for asymmetric encryption:

RSA (three authors' initials)

ElGamal

Elliptic Curve Cryptography (ECC)

Data integrity discussion

It is also faced with both passive and active.

The solution technology has hash function application.

Hash techniques are: MD (Message Digest), SHA, RIPEMD, Whirlpool.

Discussion on Information Authentication

Information authentication enables the user to determine the initiator of the information.

Information authentication code (Message Authenticaton Code-MAC)

The MAC algorithm is implemented using symmetric encryption.

Https://www.tutorialspoint.com/cryptography/cryptography_quick_guide.htm

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