Hash encryption technology in PHP and FAQs

As one of the most commonly used server-side scripting languages ​​in the world, PHP's encryption and security technology have also attracted much attention. Among them, hash encryption technology is a widely used encryption method. This article will introduce hash encryption technology in PHP in detail, as well as answers to common questions.

1. Principle of Hash Encryption Technology

Hash Algorithm is a one-way encryption algorithm. Specifically, it inputs information of any length, and after complex operations, generates a fixed-length hash value (Hash Value), the so-called hash value.

The characteristic of the hash algorithm is that no matter how big the input original data is, the output hash value has a fixed length, and the same original data input, the generated hash value is always the same. Therefore, it can easily verify the integrity of the data.

Common hash algorithms include MD5, SHA-1, SHA-256, etc. Let's take MD5 as an example to explain the basic principles of hash encryption.

MD5 is a 32-bit hash algorithm that converts input data of any length into a 128-bit output. The specific process is as follows:

1. Padding the input data so that its length becomes an integer multiple of 512 bits. The filling method is to first add a 1, and then add several 0s, so that the final length meets the requirements.
2. Split the filled data into 512-bit data blocks.
3. Perform the following four rounds of operations on each data block:

a. Round function F. For each 512-bit data block, 64 F operations are performed. The F function takes two 128-bit parameters as input and outputs a 128-bit result.

b. Addition operation. Add the output of the round function F and the intermediate result of the current data block and get a new 128-bit intermediate result.

c. Replacement operation. Replace the new 128-bit intermediate result according to specific rules.

d. Generate hash value. After processing all data blocks, a 128-bit hash value is finally generated.

2. Hash encryption function in PHP

In PHP, it is very easy to use the hash encryption algorithm. PHP comes with multiple hash functions, which are very convenient to use. The following are some of the most commonly used hash functions in PHP:

1. md5($str, $raw_output = false)

This function will do the input string $str MD5 hash, get a 32-bit hash value. If $raw_output is set to true, a 16-bit RAW binary format hash value is output.

2. sha1($str, $raw_output = false)

This function will do SHA-1 hashing of the input string $str and get a 40-bit hash value . If $raw_output is set to true, a 20-bit RAW binary format hash value is output.

3. hash($algo, $data, $raw_output = false)

This function supports multiple hashing algorithms and can customize the input data. Among them, $algo is the specified algorithm, $data is the input data, and $raw_output is whether to output RAW binary format hash value. Commonly used algorithms include MD5, SHA-1, SHA-256, etc.

4. password_hash($password, $algo, $options)

This function is a new function after PHP 5.5 and is specially used for password encryption. It supports multiple hashing algorithms, including bcrypt, argon2i, etc. The specific algorithm needs to be selected according to your own needs. $password is the password to be encrypted, $algo is the hash algorithm, and $options is the algorithm options.

5. password_verify($password, $hash)

This function is used to verify whether the password is correct. $password is the password to be verified, and $hash is the hash value of the password. This function will automatically identify the password hashing algorithm and verify it.

3. Frequently Asked Questions

1. Can hash encryption be cracked?

The hash encryption algorithm itself is an irreversible encryption method, that is, the original data cannot be deduced based on the hash value. Therefore, it has high security. However, since the input data can be of any length, all possible data can even be generated through brute force and then hashed to generate a hash value. The amount of calculation required to do this is huge and unrealistic, but it does not mean that hash encryption is absolutely secure.

2. Is there any decryption method for hash encryption?

Since hash encryption is a one-way encryption method, there is no decryption method in the usual sense. However, because there are security issues with some algorithms, brute force cracking can be carried out through certain technical means.

3. Can hash encryption be used for credential stuffing attacks?

Credential stuffing attack (Hash Collision Attack) is an attack method against hash algorithms. It takes advantage of the fact that the same input data of the hash algorithm can still generate the same hash value. Find two Different data, so that their hash values ​​are the same. This attack can disrupt the original security of the hash algorithm. However, it requires a very large amount of calculations and is often unrealistic.

4. Is hash encryption completely secure?

The hash encryption algorithm itself is a relatively safe encryption method, but due to different algorithms and implementation issues, there may still be security risks. Therefore, in practical applications, high-strength algorithms should be selected and paired with appropriate salt values ​​(Salt) and encryption options to improve security.

Summarize

Hash encryption is a very common encryption method, which can effectively ensure the integrity and privacy of data. In PHP, it is also very convenient to use hash encryption. PHP comes with multiple encryption functions. However, hash encryption is not absolutely secure, and different algorithms and encryption options need to be selected according to different scenarios to enhance security.

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