Introduction to Crypt Encryption functions (C language)

Defining functions

char * crypt (const char *key,const char * salt);

function Description

Crypt is a cryptographic function that is based on the data encryption Standard (DES) algorithm. Crypt is only available for use in passwords and is not suitable for data encryption.

Crypt () encrypts the string that the parameter key refers to, and the key string length takes only the first 8 characters, and the character beyond this length is meaningless. The parameter salt is a two-character string consisting of A-Z, A-Z, 0-9, "." and "/", which is used to determine the use of 4096 (A-Z, A-Z, 0-9, ".") and "/" a total of 64 characters, 64 squared to 4096, which one of the different built-in tables. When a function executes successfully, it returns a pointer to the encoded string, and the string that the parameter key refers to does not change. The encoded string has a length of 13 characters, and the first two characters are strings represented by the parameter salt.

return value

Returns a string that points to a null-terminated password.

Note Compile-time to add the-lcrypt option at the end.

/**

* Gcc-o Crypt Crypt.c-lcrypt

*/

#include <unistd.h>

#include <crypt.h>

#include <string.h>

int main (void)

{

Char passwd[13];

Char *key;

Char slat[2];

Key = Getpass ("Input-Password:");

Slat[0] = key[0];

SLAT[1] = key[1];

strcpy (Passwd,crypt (Key,slat));

Key = Getpass ("Input Second Password:");

Slat[0] = passwd[0];

SLAT[1] = passwd[1];

printf ("After Crypt (), 1st passwd:%s/n", passwd);

printf ("After Crypt (), 2nd passwd:%s/n", Crypt (Key,slat));

return 0;

}

Program Run Result: (Note: two times as input)

Input Password:

Input Second Password:

After crypt (), 1st passwd:asZvhAtTX.i7g

After crypt (), 2nd passwd:asZvhAtTX.i7g

Related functions: Crypt
Table header file: #include <unistd.h>
function definition: char *getpass (const char *prompt)
Function Description: Getpass () Displays the string that the parameter prompt refers to, and then reads the password entered from the/dev/tty, and then reads the password from the standard input device if it cannot be read from the/dev/tty. The password length entered is limited to 128 characters, contains the ending character null, characters longer than the length and the newline character/n will be ignored. When you enter a password, Getpass () turns off the character response and ignores signals such as ctrl-c or ctrl-z
Return value: Returns a string that points to a null-terminated password
Additional note: For system security considerations, in the same way after using Getpass () to enter a password, the password is best processed as soon as possible, and then clear the password string
Example parameter crypt ()