Some summaries about encryption functions in php

The functions to implement encryption in php are nothing more than the following: 1,md5() 2.sha1() 3.crc32() 4.crypt() 5. uniqid()

1, md5() function Definition and usage The md5() function calculates the MD5 hash of a string. The md5() function uses RSA data security, including the MD5 message digest algorithm. Returns the calculated MD5 hash on success, false on failure.

Grammar md5(string,raw)

Parameter Description string Required. Specifies the string to be calculated. raw raw

Optional. Specify hexadecimal or binary output format: TRUE - raw 16-character binary format FALSE - Default. 32-character hexadecimal number Note: This parameter was added in PHP 5.0.

Example:

<?php
$str = "Hello";
echo md5($str);
?>

Output: 8b1a9953c4611296a827abf8c47804d7

2, sha1() function:

Definition and usage The sha1() function calculates the SHA-1 hash of a string. The sha1() function uses the US Secure Hash algorithm 1. Returns the calculated SHA-1 hash on success, false on failure.

Grammar sha1(string,raw)

Parameter Description string required. Specifies the string to be calculated. charlist Optional. Specify hexadecimal or binary output format: TRUE - raw 20-character binary format FALSE - Default. 40 character hexadecimal number

Note: This parameter was added in PHP 5.0. 3. crc32() function: Definition and usage The crc32() function computes the crc32 polynomial of a string. This function can be used to verify data integrity.

Grammar crc32(string) string required. Specifies the string to be calculated.

Instructions Generates a 32-bit cyclic redundancy check code polynomial for the string parameter. This is typically used to check whether the transmitted data is complete. Tips and Notes Tip: Since PHP's integers are signed, many crc32 check codes will return negative integers, so you need to use sprintf() or printf()'s "%u" formatter to get the character representing the unsigned crc32 check code string.

Example that will output the result of crc32() with and without the "%u" formatter (note that the result is the same):

<?php
$str = crc32("Hello world!");
echo 'Without %u: '.$str."<br />";
echo 'With %u: ';
printf("%u",$str);
?>

Output: Without %u: 461707669 With %u: 461707669

Example 2, in this example, the results of crc32() will be output with and without the "%u" format character (note that the results are different):

<?php
$str = crc32("Hello world.");
echo 'Without %u: '.$str."<br />";
echo 'With %u: ';
printf("%u",$str);
?>

Output: Without %u: -1959132156 With %u: 2335835140 4. uniqid() function: Definition and usage The uniqid() function generates a unique ID based on the current time in microseconds.

Grammar uniqid(prefix,more_entropy) prefix is ​​optional. Specifies the prefix for the ID. This parameter is useful if both scripts generate IDs at the same subtlety. more_entropy is optional. Specifies more entropy at the end of the return value.

Instructions If the prefix parameter is empty, the returned string is 13 strings long. If the more_entropy parameter is set to true, it is 23 strings long. If the more_entropy parameter is set to true, additional entropy is added to the end of the return value (using the combined linear congruence generator), which makes the result more unique.

Return value Returns the unique identifier as a string.

Tips and Notes Note: The ID generated by this function is suboptimal because it is based on system time. To generate an absolutely unique ID, use the md5() function (find it in the String Functions Reference).

Example:

<?php
echo uniqid();
?>

The output is similar to: 4415297e3af8c 5. crypt() function: Definition and usage The crypt() function returns a string encrypted using DES, Blowfish, or MD5. This function behaves differently on different operating systems, and some operating systems support more than one algorithm type. At installation time, PHP checks what algorithms are available and what algorithms are used.

Grammar crypt(str,salt) str required. Specifies the string to be encoded. salt

Optional. A string used to increase the number of characters being encoded to make the encoding more secure. If no salt argument is provided, one will be randomly generated each time the function is called.

Tips and Notes Tip: There is no decryption function. The crypt() function uses a one-way algorithm.

Examples that will test different algorithms:

<?php
if (CRYPT_STD_DES == 1)
{
echo "Standard DES: ".crypt("hello world")."\n<br />";
}
else
{
echo "Standard DES not supported.\n<br />";
}

if (CRYPT_EXT_DES == 1)
{
echo "Extended DES: ".crypt("hello world")."\n<br />";
}
else
{
echo "Extended DES not supported.\n<br />";
}

if (CRYPT_MD5 == 1)
{
echo "MD5: ".crypt("hello world")."\n<br />";
}
else
{
echo "MD5 not supported.\n<br />";
}

if (CRYPT_BLOWFISH == 1)
{
echo "Blowfish: ".crypt("hello world");
}
else
{
echo "Blowfish DES not supported.";
}
?>

Output similar to (OS dependent): Standard DES: $1$r35.Y52.$iyiFuvM.zFGsscpU0aZ4e. Extended DES not supported. MD5: $1$BN1.0I2.$8oBI/4mufxK6Tq89M12mk/ Blowfish DES not supported.

Note, the exact algorithm depends on the format and length of the salt parameter.

Here are some constants used with the crypt() function. These constants are set by PHP at installation time: [CRYPT_SALT_LENGTH] [CRYPT_STD_DES] [CRYPT_EXT_DES] [CRYPT_MD5] [CRYPT_BLOWFISH]