Why you use random numbers to avoid replay attacks

Separate random numbers.

Replay attacks cannot be avoided.

Random numbers are generally mixed with signature encryption and background verification to make it more difficult to crack and replay.

Replay attacks

Also known as a replay attack.

Replay Attack or Freshness Attack.

Freshness attacks) are used to deceive the system by sending a packet that has been received by the target host, which is mainly used in the authentication process to destroy the correctness of authentication.

From the definition of replay attack, we can see that the data submitted to the server by the replay attack was once valid, how to prevent this kind of data, give a specific random number to a specific information, and this random number is stored in the server, before verifying the user information, the random number will be verified first, if it is found that the submitted random number is different from the server saved, the information is invalid through this method to prevent the replay attack.

Commonly used defense against replay attacks does not directly expose random numbers, which are generally used in md5, hash (digital signature.

, for example, in MD5 encryption of valid values.

If the username is test, the password for test may be MD5 ("test","test", random number), so that the random value will not be exposed when the direct transmission is transmitted, and the system finds that the MD5 signature and the system signature are different when the hacker submits the replay attack, which can be considered a replay attack.

Of course, the spear and shield exist, and it is possible that the value is just assigned to the user again, and the replay attack may be successful, but this probability can be regarded as 0 in scientific calculation, and as the number of digits of the random number increases, the probability will continue to decrease.

Replay attacks, also known as replay attacks, replay attacks, or freshness attacks, refer to the purpose of an attacker sending a packet that has been received by the destination host to deceive the system, which is mainly used in the identity authentication process to destroy the correctness of authentication.

It is a type of attack that constantly repeats a valid data transmission maliciously or fraudulently, and the replay attack can be carried out by the initiator or by the adversary who intercepts and retransmits that data. An attacker can use network snooping or other means to steal authentication credentials and then resend them to the authentication server. From this explanation, encryption can effectively prevent session hijacking, but it cannot prevent replay attacks.

Replay attacks can occur during any network communication. Replay attacks are one of the most common attack methods used by hackers in the computer world, and their written definition is abstract to people who do not understand cryptography.

You're a god for it, how can you prevent others from attacking your network?

TLS has an anti-replay attack mechanism.

Encryption, timestamp, each packet must have a package sequence number, add 1 in the same direction each time, and receive a duplicate sequence number is considered an attack, which can resist replay attacks. In addition, with the help of HTTPS TLS and its own mechanism, the integrity of the message is guaranteed, and the replay attack can be resisted. Due to encryption, the other party cannot see the plaintext content either.

2.The client generates a string of random numbers r1 and sends it to the server, which determines whether this r1 is a duplicate and then generates a key according to the algorithm (r1+r2). It is best to combine it with a verification mechanism.

3.HTTPS can be attacked by man-in-the-middle, and Fiddler can intercept and restore the plaintext by replacing the certificate. Asymmetric encryption (e.g. RSA) is a good idea, but it has to be protected from others.

Further reading: Transport Layer Secure (TLS) is used to provide confidentiality and data integrity between two communication applications.

The protocol consists of two layers: the TLS Record Protocol and the TLS Handshake Protocol.

1. Establish a session mechanism, which is reflected in the deployment of SSL certificates, and strongly require the implementation of feature security configuration.

2. Verify the separation of elements, and use OV or EV certificates to ensure security.