setkey(3)

1encrypt(3)                 Library Functions Manual                 encrypt(3)
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NAME

6       encrypt, setkey, encrypt_r, setkey_r - encrypt 64-bit messages
7

LIBRARY

9       Password hashing library (libcrypt, -lcrypt)
10

SYNOPSIS

12       #define _XOPEN_SOURCE       /* See feature_test_macros(7) */
13       #include <unistd.h>
14
15       [[deprecated]] void encrypt(char block[64], int edflag);
16
17       #define _XOPEN_SOURCE       /* See feature_test_macros(7) */
18       #include <stdlib.h>
19
20       [[deprecated]] void setkey(const char *key);
21
22       #define _GNU_SOURCE         /* See feature_test_macros(7) */
23       #include <crypt.h>
24
25       [[deprecated]] void setkey_r(const char *key, struct crypt_data *data);
26       [[deprecated]] void encrypt_r(char *block, int edflag,
27                                     struct crypt_data *data);
28

DESCRIPTION

30       These  functions  encrypt  and  decrypt  64-bit messages.  The setkey()
31       function sets the key used by encrypt().  The key argument used here is
32       an  array  of  64 bytes, each of which has numerical value 1 or 0.  The
33       bytes key[n] where n=8*i-1 are  ignored,  so  that  the  effective  key
34       length is 56 bits.
35
36       The  encrypt()  function modifies the passed buffer, encoding if edflag
37       is 0, and decoding if 1 is being passed.  Like the key  argument,  also
38       block  is  a  bit vector representation of the actual value that is en‐
39       coded.  The result is returned in that same vector.
40
41       These two functions are not reentrant, that is, the key data is kept in
42       static storage.  The functions setkey_r() and encrypt_r() are the reen‐
43       trant versions.  They use the following structure to hold the key data:
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45           struct crypt_data {
46               char keysched[16 * 8];
47               char sb0[32768];
48               char sb1[32768];
49               char sb2[32768];
50               char sb3[32768];
51               char crypt_3_buf[14];
52               char current_salt[2];
53               long current_saltbits;
54               int  direction;
55               int  initialized;
56           };
57
58       Before calling setkey_r() set data->initialized to zero.
59

RETURN VALUE

61       These functions do not return any value.
62

ERRORS

64       Set errno to zero before calling the above functions.  On success,  er‐
65       rno is unchanged.
66
67       ENOSYS The  function  is  not provided.  (For example because of former
68              USA export restrictions.)
69

ATTRIBUTES

71       For an  explanation  of  the  terms  used  in  this  section,  see  at‐
72       tributes(7).
73
74       ┌───────────────────────────────┬───────────────┬──────────────────────┐
75       │Interface                      │ Attribute     │ Value                │
76       ├───────────────────────────────┼───────────────┼──────────────────────┤
77       │encrypt(), setkey()            │ Thread safety │ MT-Unsafe race:crypt │
78       ├───────────────────────────────┼───────────────┼──────────────────────┤
79       │encrypt_r(), setkey_r()        │ Thread safety │ MT-Safe              │
80       └───────────────────────────────┴───────────────┴──────────────────────┘
81

STANDARDS

83       encrypt()
84       setkey()
85              POSIX.1-2008.
86
87       encrypt_r()
88       setkey_r()
89              None.
90

HISTORY

92       Removed in glibc 2.28.
93
94       Because they employ the DES block cipher, which is no longer considered
95       secure, these functions were removed from glibc.   Applications  should
96       switch to a modern cryptography library, such as libgcrypt.
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98       encrypt()
99       setkey()
100              POSIX.1-2001, SUS, SVr4.
101
102   Availability in glibc
103       See crypt(3).
104
105   Features in glibc
106       In glibc 2.2, these functions use the DES algorithm.
107

EXAMPLES

109       #define _XOPEN_SOURCE
110       #include <crypt.h>
111       #include <stdio.h>
112       #include <stdlib.h>
113       #include <unistd.h>
114
115       int
116       main(void)
117       {
118           char key[64];
119           char orig[9] = "eggplant";
120           char buf[64];
121           char txt[9];
122
123           for (size_t i = 0; i < 64; i++) {
124               key[i] = rand() & 1;
125           }
126
127           for (size_t i = 0; i < 8; i++) {
128               for (size_t j = 0; j < 8; j++) {
129                   buf[i * 8 + j] = orig[i] >> j & 1;
130               }
131               setkey(key);
132           }
133           printf("Before encrypting: %s\n", orig);
134
135           encrypt(buf, 0);
136           for (size_t i = 0; i < 8; i++) {
137               for (size_t j = 0, txt[i] = '\0'; j < 8; j++) {
138                   txt[i] |= buf[i * 8 + j] << j;
139               }
140               txt[8] = '\0';
141           }
142           printf("After encrypting:  %s\n", txt);
143
144           encrypt(buf, 1);
145           for (size_t i = 0; i < 8; i++) {
146               for (size_t j = 0, txt[i] = '\0'; j < 8; j++) {
147                   txt[i] |= buf[i * 8 + j] << j;
148               }
149               txt[8] = '\0';
150           }
151           printf("After decrypting:  %s\n", txt);
152           exit(EXIT_SUCCESS);
153       }
154