man3/encrypt.3

   1 .\" Copyright 2000 Nicolás Lichtmaier <nick@debian.org>
   2 .\" Created 2000-07-22 00:52-0300
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  25 .\" Modified 2002-07-23 19:21:35 CEST 2002 Walter Harms
  26 .\" <walter.harms@informatik.uni-oldenburg.de>
  27 .\"
  28 .\" Modified 2003-04-04, aeb
  29 .\"
  30 .TH ENCRYPT 3 2018-04-30 "" "Linux Programmer's Manual"
  31 .SH NAME
  32 encrypt, setkey, encrypt_r, setkey_r \- encrypt 64-bit messages
  33 .SH SYNOPSIS
  34 .nf
  35 .BR "#define _XOPEN_SOURCE" "       /* See feature_test_macros(7) */"
  36 .B #include <unistd.h>
  37 .PP
  38 .BI "void encrypt(char " block "[64], int " edflag );
  39
  40 .BR "#define _XOPEN_SOURCE" "       /* See feature_test_macros(7) */"
  41 .B #include <stdlib.h>
  42 .PP
  43 .BI "void setkey(const char *" key );
  44
  45 .BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
  46 .B "#include <crypt.h>"
  47 .PP
  48 .BI "void setkey_r(const char *" key ", struct crypt_data *" data );
  49 .BI "void encrypt_r(char *" block ", int " edflag \
  50 ", struct crypt_data *" data );
  51 .fi
  52 .PP
  53 Each of these requires linking with \fI\-lcrypt\fP.
  54 .SH DESCRIPTION
  55 These functions encrypt and decrypt 64-bit messages.
  56 The
  57 .BR setkey ()
  58 function sets the key used by
  59 .BR encrypt ().
  60 The
  61 .I key
  62 argument used here is an array of 64 bytes, each of which has
  63 numerical value 1 or 0.
  64 The bytes key[n] where n=8*i-1 are ignored,
  65 so that the effective key length is 56 bits.
  66 .PP
  67 The
  68 .BR encrypt ()
  69 function modifies the passed buffer, encoding if
  70 .I edflag
  71 is 0, and decoding if 1 is being passed.
  72 Like the
  73 .I key
  74 argument, also
  75 .I block
  76 is a bit vector representation of the actual value that is encoded.
  77 The result is returned in that same vector.
  78 .PP
  79 These two functions are not reentrant, that is, the key data is
  80 kept in static storage.
  81 The functions
  82 .BR setkey_r ()
  83 and
  84 .BR encrypt_r ()
  85 are the reentrant versions.
  86 They use the following
  87 structure to hold the key data:
  88 .PP
  89 .in +4n
  90 .EX
  91 struct crypt_data {
  92     char     keysched[16 * 8];
  93     char     sb0[32768];
  94     char     sb1[32768];
  95     char     sb2[32768];
  96     char     sb3[32768];
  97     char     crypt_3_buf[14];
  98     char     current_salt[2];
  99     long int current_saltbits;
 100     int      direction;
 101     int      initialized;
 102 };
 103 .EE
 104 .in
 105 .PP
 106 Before calling
 107 .BR setkey_r ()
 108 set
 109 .I data\->initialized
 110 to zero.
 111 .SH RETURN VALUE
 112 These functions do not return any value.
 113 .SH ERRORS
 114 Set
 115 .I errno
 116 to zero before calling the above functions.
 117 On success, it is unchanged.
 118 .TP
 119 .B ENOSYS
 120 The function is not provided.
 121 (For example because of former USA export restrictions.)
 122 .SH VERSIONS
 123 Because they employ the DES block cipher,
 124 which is no longer considered secure,
 125 .BR crypt (),
 126 .BR crypt_r (),
 127 .BR setkey (),
 128 and
 129 .BR setkey_r ()
 130 were removed in glibc 2.28.
 131 Applications should switch to a modern cryptography library, such as
 132 .BR libgcrypt .
 133 .SH ATTRIBUTES
 134 For an explanation of the terms used in this section, see
 135 .BR attributes (7).
 136 .TS
 137 allbox;
 138 lbw23 lb lb
 139 l l l.
 140 Interface       Attribute       Value
 141 T{
 142 .BR encrypt (),
 143 .BR setkey ()
 144 T}      Thread safety   MT-Unsafe race:crypt
 145 T{
 146 .BR encrypt_r (),
 147 .BR setkey_r ()
 148 T}      Thread safety   MT-Safe
 149 .TE
 150 .SH CONFORMING TO
 151 .BR encrypt (),
 152 .BR setkey ():
 153 POSIX.1-2001, POSIX.1-2008, SUS, SVr4.
 154 .PP
 155 The functions
 156 .BR encrypt_r ()
 157 and
 158 .BR setkey_r ()
 159 are GNU extensions.
 160 .SH NOTES
 161 .SS Availability in glibc
 162 See
 163 .BR crypt (3).
 164 .SS Features in glibc
 165 In glibc 2.2, these functions use the DES algorithm.
 166 .SH EXAMPLE
 167 .EX
 168 #define _XOPEN_SOURCE
 169 #include <stdio.h>
 170 #include <stdlib.h>
 171 #include <unistd.h>
 172 #include <crypt.h>
 173
 174 int
 175 main(void)
 176 {
 177     char key[64];
 178     char orig[9] = "eggplant";
 179     char buf[64];
 180     char txt[9];
 181     int i, j;
 182
 183     for (i = 0; i < 64; i++) {
 184         key[i] = rand() & 1;
 185     }
 186
 187     for (i = 0; i < 8; i++) {
 188         for (j = 0; j < 8; j++) {
 189             buf[i * 8 + j] = orig[i] >> j & 1;
 190         }
 191         setkey(key);
 192     }
 193     printf("Before encrypting: %s\en", orig);
 194
 195     encrypt(buf, 0);
 196     for (i = 0; i < 8; i++) {
 197         for (j = 0, txt[i] = \(aq\e0\(aq; j < 8; j++) {
 198             txt[i] |= buf[i * 8 + j] << j;
 199         }
 200         txt[8] = \(aq\e0\(aq;
 201     }
 202     printf("After encrypting:  %s\en", txt);
 203
 204     encrypt(buf, 1);
 205     for (i = 0; i < 8; i++) {
 206         for (j = 0, txt[i] = \(aq\e0\(aq; j < 8; j++) {
 207             txt[i] |= buf[i * 8 + j] << j;
 208         }
 209         txt[8] = \(aq\e0\(aq;
 210     }
 211     printf("After decrypting:  %s\en", txt);
 212     exit(EXIT_SUCCESS);
 213 }
 214 .EE
 215 .SH SEE ALSO
 216 .BR cbc_crypt (3),
 217 .BR crypt (3),
 218 .BR ecb_crypt (3),
 219 .\" .BR fcrypt (3)