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 2015-08-08 "" "Linux Programmer's Manual"
  31 .SH NAME
  32 encrypt, setkey, encrypt_r, setkey_r \- encrypt 64-bit messages
  33 .SH SYNOPSIS
  34 .BR "#define _XOPEN_SOURCE" "       /* See feature_test_macros(7) */"
  35 .br
  36 .B #include <unistd.h>
  37 .sp
  38 .BI "void encrypt(char " block "[64], int " edflag );
  39 .sp
  40 .BR "#define _XOPEN_SOURCE" "       /* See feature_test_macros(7) */"
  41 .br
  42 .B #include <stdlib.h>
  43 .sp
  44 .BI "void setkey(const char *" key );
  45 .sp
  46 .BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
  47 .br
  48 .B "#include <crypt.h>"
  49 .sp
  50 .BI "void setkey_r(const char *" key ", struct crypt_data *" data );
  51 .br
  52 .BI "void encrypt_r(char *" block ", int " edflag \
  53 ", struct crypt_data *" data );
  54 .sp
  55 Each of these requires linking with \fI\-lcrypt\fP.
  56 .SH DESCRIPTION
  57 These functions encrypt and decrypt 64-bit messages.
  58 The
  59 .BR setkey ()
  60 function sets the key used by
  61 .BR encrypt ().
  62 The
  63 .I key
  64 argument used here is an array of 64 bytes, each of which has
  65 numerical value 1 or 0.
  66 The bytes key[n] where n=8*i-1 are ignored,
  67 so that the effective key length is 56 bits.
  68 .PP
  69 The
  70 .BR encrypt ()
  71 function modifies the passed buffer, encoding if
  72 .I edflag
  73 is 0, and decoding if 1 is being passed.
  74 Like the
  75 .I key
  76 argument, also
  77 .I block
  78 is a bit vector representation of the actual value that is encoded.
  79 The result is returned in that same vector.
  80 .PP
  81 These two functions are not reentrant, that is, the key data is
  82 kept in static storage.
  83 The functions
  84 .BR setkey_r ()
  85 and
  86 .BR encrypt_r ()
  87 are the reentrant versions.
  88 They use the following
  89 structure to hold the key data:
  90 .in +4n
  91 .nf
  92
  93 struct crypt_data {
  94     char     keysched[16 * 8];
  95     char     sb0[32768];
  96     char     sb1[32768];
  97     char     sb2[32768];
  98     char     sb3[32768];
  99     char     crypt_3_buf[14];
 100     char     current_salt[2];
 101     long int current_saltbits;
 102     int      direction;
 103     int      initialized;
 104 };
 105 .fi
 106 .in
 107 .PP
 108 Before calling
 109 .BR setkey_r ()
 110 set
 111 .I data\->initialized
 112 to zero.
 113 .SH RETURN VALUE
 114 These functions do not return any value.
 115 .SH ERRORS
 116 Set
 117 .I errno
 118 to zero before calling the above functions.
 119 On success, it is unchanged.
 120 .TP
 121 .B ENOSYS
 122 The function is not provided.
 123 (For example because of former USA export restrictions.)
 124 .SH ATTRIBUTES
 125 For an explanation of the terms used in this section, see
 126 .BR attributes (7).
 127 .TS
 128 allbox;
 129 lbw23 lb lb
 130 l l l.
 131 Interface       Attribute       Value
 132 T{
 133 .BR encrypt (),
 134 .BR setkey ()
 135 T}      Thread safety   MT-Unsafe race:crypt
 136 T{
 137 .BR encrypt_r (),
 138 .BR setkey_r ()
 139 T}      Thread safety   MT-Safe
 140 .TE
 141 .SH CONFORMING TO
 142 .BR encrypt (),
 143 .BR setkey ():
 144 POSIX.1-2001, POSIX.1-2008, SUS, SVr4.
 145
 146 The functions
 147 .BR encrypt_r ()
 148 and
 149 .BR setkey_r ()
 150 are GNU extensions.
 151 .SH NOTES
 152 In glibc 2.2, these functions use the DES algorithm.
 153 .SH EXAMPLE
 154 .nf
 155 #define _XOPEN_SOURCE
 156 #include <stdio.h>
 157 #include <stdlib.h>
 158 #include <unistd.h>
 159 #include <crypt.h>
 160
 161 int
 162 main(void)
 163 {
 164     char key[64];
 165     char orig[9] = "eggplant";
 166     char buf[64];
 167     char txt[9];
 168     int i, j;
 169
 170     for (i = 0; i < 64; i++) {
 171         key[i] = rand() & 1;
 172     }
 173
 174     for (i = 0; i < 8; i++) {
 175         for (j = 0; j < 8; j++) {
 176             buf[i * 8 + j] = orig[i] >> j & 1;
 177         }
 178         setkey(key);
 179     }
 180     printf("Before encrypting: %s\\n", orig);
 181
 182     encrypt(buf, 0);
 183     for (i = 0; i < 8; i++) {
 184         for (j = 0, txt[i] = \(aq\\0\(aq; j < 8; j++) {
 185             txt[i] |= buf[i * 8 + j] << j;
 186         }
 187         txt[8] = \(aq\\0\(aq;
 188     }
 189     printf("After encrypting:  %s\\n", txt);
 190
 191     encrypt(buf, 1);
 192     for (i = 0; i < 8; i++) {
 193         for (j = 0, txt[i] = \(aq\\0\(aq; j < 8; j++) {
 194             txt[i] |= buf[i * 8 + j] << j;
 195         }
 196         txt[8] = \(aq\\0\(aq;
 197     }
 198     printf("After decrypting:  %s\\n", txt);
 199     exit(EXIT_SUCCESS);
 200 }
 201 .fi
 202 .SH SEE ALSO
 203 .BR cbc_crypt (3),
 204 .BR crypt (3),
 205 .BR ecb_crypt (3),
 206 .\" .BR fcrypt (3)