encrypt(3)
NAME
encrypt, setkey, encrypt_r, setkey_r - encrypt 64-bit messages
SYNOPSIS
#define _XOPEN_SOURCE /* See feature_test_macros(7) */ #include <unistd.h> void encrypt(char block[64], int edflag); #define _XOPEN_SOURCE /* See feature_test_macros(7) */ #include <stdlib.h> void setkey(const char *key); #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <crypt.h> void setkey_r(const char *key, struct crypt_data *data); void encrypt_r(char *block, int edflag, struct crypt_data *data); Each of these requires linking with -lcrypt.
DESCRIPTION
These functions encrypt and decrypt 64-bit messages. The setkey()
function sets the key used by encrypt(). The key argument used here is
an array of 64 bytes, each of which has numerical value 1 or 0. The
bytes key[n] where n=8*i-1 are ignored, so that the effective key
length is 56 bits.
The encrypt() function modifies the passed buffer, encoding if edflag
is 0, and decoding if 1 is being passed. Like the key argument, also
block is a bit vector representation of the actual value that is
encoded. The result is returned in that same vector.
These two functions are not reentrant, that is, the key data is kept in
static storage. The functions setkey_r() and encrypt_r() are the
reentrant versions. They use the following structure to hold the key
data:
struct crypt_data {
char keysched[16 * 8];
char sb0[32768];
char sb1[32768];
char sb2[32768];
char sb3[32768];
char crypt_3_buf[14];
char current_salt[2];
long int current_saltbits;
int direction;
int initialized;
};
Before calling setkey_r() set data->initialized to zero.
RETURN VALUE
These functions do not return any value.
ERRORS
Set errno to zero before calling the above functions. On success, it
is unchanged.
ENOSYS The function is not provided. (For example because of former
USA export restrictions.)
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7). Interface Attribute Value encrypt(), setkey() Thread safety MT-Unsafe race:crypt encrypt_r(), setkey_r() Thread safety MT-Safe
CONFORMING TO
encrypt(), setkey(): POSIX.1-2001, POSIX.1-2008, SUS, SVr4. The functions encrypt_r() and setkey_r() are GNU extensions.
NOTES
In glibc 2.2, these functions use the DES algorithm.
EXAMPLE
#define _XOPEN_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <crypt.h>
int
main(void)
{
char key[64];
char orig[9] = "eggplant";
char buf[64];
char txt[9];
int i, j;
for (i = 0; i < 64; i++) {
key[i] = rand() & 1;
}
for (i = 0; i < 8; i++) {
for (j = 0; j < 8; j++) {
buf[i * 8 + j] = orig[i] >> j & 1;
}
setkey(key);
}
printf("Before encrypting: %s\n", orig);
encrypt(buf, 0);
for (i = 0; i < 8; i++) {
for (j = 0, txt[i] = '\0'; j < 8; j++) {
txt[i] |= buf[i * 8 + j] << j;
}
txt[8] = '\0';
}
printf("After encrypting: %s\n", txt);
encrypt(buf, 1);
for (i = 0; i < 8; i++) {
for (j = 0, txt[i] = '\0'; j < 8; j++) {
txt[i] |= buf[i * 8 + j] << j;
}
txt[8] = '\0';
}
printf("After decrypting: %s\n", txt);
exit(EXIT_SUCCESS);
}
SEE ALSO
cbc_crypt(3), crypt(3), ecb_crypt(3),
COLOPHON
This page is part of release 4.09 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
2015-08-08 ENCRYPT(3)
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
