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Hash functions play a vital role in front-end security, mainly in the following aspects:

1. Password storage

When users create accounts or change passwords in the front-end application, it is very dangerous to directly store plain text passwords. Instead, the front-end uses a hash function (such as SHA-256 or SHA-512) to convert the password into a fixed-length hash value, and then sends this hash value to the back-end for storage. In this way, even if the database is leaked, it is difficult for attackers to reverse the original password from the hash value.

2. Data integrity check

Hash functions can be used to ensure that data has not been tampered with during transmission. The front end can calculate the hash value of the data to be sent and send it along with the data. After the back end receives the data, it calculates the hash value again and compares it with the hash value sent by the front end. If the two match, the data has not been modified during transmission.

3. Prevent replay attacks

In some requests that require authentication, the front end can generate a random string (called a nonce) and send it with the user's request. This nonce is hashed and stored on the back end. If there are subsequent repeated requests, the back end can check whether the nonce has been used to prevent replay attacks.

4. Verify documents and resources

The front end can use hash functions to verify the integrity of files or resources downloaded from the server. For example, using the Subresource Integrity (SRI) function, developers can specify a hash value in the HTML tag, and the browser will automatically calculate the hash value when loading the resource and compare it with the specified value to ensure that the resource has not been maliciously tampered with.

5. Bloom Filter

In some cases, the front end may use a Bloom filter to quickly determine whether an element exists in a set. Bloom filters use multiple different hash functions to reduce false positives. Although it may produce false positives, it will not produce false negatives, which is very useful when processing large amounts of data.

6. Web Application Firewall (WAF)

Hash functions are also used in web application firewalls to detect and block malicious requests. WAF can maintain a blacklist containing hash values ​​of known malicious request patterns. When a new request is received, WAF hashes the request and then checks whether the hash value is in the blacklist.

7. Protect sensitive information

When dealing with sensitive information, such as credit card numbers or personally identifiable information, the front end can use a hash function to create a hash value of this information, and then use this hash value for comparison or as an identifier instead of using the original data directly, thereby increasing security.

in conclusion

Hash functions enhance the security of front-end applications by providing a one-way and fixed output method, especially in dealing with user authentication, data integrity and privacy protection. However, it is important to note that although hash functions provide strong security guarantees, they are not foolproof, especially for password storage, and it is best to use salt in combination to further increase the difficulty of cracking.