1ENCRYPT(3) Linux Programmer's Manual ENCRYPT(3)
2
6 encrypt, setkey, encrypt_r, setkey_r - encrypt 64-bit messages
7
9 #define _XOPEN_SOURCE /* See feature_test_macros(7) */
10 #include <unistd.h>
11 void encrypt(char block[64], int edflag);
13 #define _XOPEN_SOURCE /* See feature_test_macros(7) */
15 #include <stdlib.h>
16 void setkey(const char *key);
18 #define _GNU_SOURCE /* See feature_test_macros(7) */
20 #include <crypt.h>
21 void setkey_r(const char *key, struct crypt_data *data);
23 void encrypt_r(char *block, int edflag, struct crypt_data *data);
24 Each of these requires linking with -lcrypt.
26
28 These functions encrypt and decrypt 64-bit messages. The setkey()
29 function sets the key used by encrypt(). The key argument used here is
30 an array of 64 bytes, each of which has numerical value 1 or 0. The
31 bytes key[n] where n=8*i-1 are ignored, so that the effective key
32 length is 56 bits.
33 The encrypt() function modifies the passed buffer, encoding if edflag
35 is 0, and decoding if 1 is being passed. Like the key argument, also
36 block is a bit vector representation of the actual value that is en‐
37 coded. The result is returned in that same vector.
38 These two functions are not reentrant, that is, the key data is kept in
40 static storage. The functions setkey_r() and encrypt_r() are the reen‐
41 trant versions. They use the following structure to hold the key data:
42 struct crypt_data {
44 char keysched[16 * 8];
45 char sb0[32768];
46 char sb1[32768];
47 char sb2[32768];
48 char sb3[32768];
49 char crypt_3_buf[14];
50 char current_salt[2];
51 long current_saltbits;
52 int direction;
53 int initialized;
54 };
55 Before calling setkey_r() set data->initialized to zero.
57
59 These functions do not return any value.
60
62 Set errno to zero before calling the above functions. On success, it
63 is unchanged.
64 ENOSYS The function is not provided. (For example because of former
66 USA export restrictions.)
67
69 Because they employ the DES block cipher, which is no longer considered
70 secure, crypt(), crypt_r(), setkey(), and setkey_r() were removed in
71 glibc 2.28. Applications should switch to a modern cryptography li‐
72 brary, such as libgcrypt.
73
75 For an explanation of the terms used in this section, see at‐
76 tributes(7).
77 ┌────────────────────────┬───────────────┬──────────────────────┐
79 │Interface │ Attribute │ Value │
80 ├────────────────────────┼───────────────┼──────────────────────┤
81 │encrypt(), setkey() │ Thread safety │ MT-Unsafe race:crypt │
82 ├────────────────────────┼───────────────┼──────────────────────┤
83 │encrypt_r(), setkey_r() │ Thread safety │ MT-Safe │
84 └────────────────────────┴───────────────┴──────────────────────┘
86 encrypt(), setkey(): POSIX.1-2001, POSIX.1-2008, SUS, SVr4.
87 The functions encrypt_r() and setkey_r() are GNU extensions.
89
91 Availability in glibc
92 See crypt(3).
93 Features in glibc
95 In glibc 2.2, these functions use the DES algorithm.
96
98 #define _XOPEN_SOURCE
99 #include <stdio.h>
100 #include <stdlib.h>
101 #include <unistd.h>
102 #include <crypt.h>
103 int
105 main(void)
106 {
107 char key[64];
108 char orig[9] = "eggplant";
109 char buf[64];
110 char txt[9];
111 for (int i = 0; i < 64; i++) {
113 key[i] = rand() & 1;
114 }
115 for (int i = 0; i < 8; i++) {
117 for (int j = 0; j < 8; j++) {
118 buf[i * 8 + j] = orig[i] >> j & 1;
119 }
120 setkey(key);
121 }
122 printf("Before encrypting: %s\n", orig);
123 encrypt(buf, 0);
125 for (int i = 0; i < 8; i++) {
126 for (int j = 0, txt[i] = '\0'; j < 8; j++) {
127 txt[i] |= buf[i * 8 + j] << j;
128 }
129 txt[8] = '\0';
130 }
131 printf("After encrypting: %s\n", txt);
132 encrypt(buf, 1);
134 for (int i = 0; i < 8; i++) {
135 for (int j = 0, txt[i] = '\0'; j < 8; j++) {
136 txt[i] |= buf[i * 8 + j] << j;
137 }
138 txt[8] = '\0';
139 }
140 printf("After decrypting: %s\n", txt);
141 exit(EXIT_SUCCESS);
142 }
143
145 cbc_crypt(3), crypt(3), ecb_crypt(3),
146
148 This page is part of release 5.10 of the Linux man-pages project. A
149 description of the project, information about reporting bugs, and the
150 latest version of this page, can be found at
151 https://www.kernel.org/doc/man-pages/.
152 2020-11-01 ENCRYPT(3)