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 2017-09-15 "" "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 ATTRIBUTES
 123 For an explanation of the terms used in this section, see
 124 .BR attributes (7).
 125 .TS
 126 allbox;
 127 lbw23 lb lb
 128 l l l.
 129 Interface       Attribute       Value
 130 T{
 131 .BR encrypt (),
 132 .BR setkey ()
 133 T}      Thread safety   MT-Unsafe race:crypt
 134 T{
 135 .BR encrypt_r (),
 136 .BR setkey_r ()
 137 T}      Thread safety   MT-Safe
 138 .TE
 139 .SH CONFORMING TO
 140 .BR encrypt (),
 141 .BR setkey ():
 142 POSIX.1-2001, POSIX.1-2008, SUS, SVr4.
 143 .PP
 144 The functions
 145 .BR encrypt_r ()
 146 and
 147 .BR setkey_r ()
 148 are GNU extensions.
 149 .SH NOTES
 150 .SS Availability in glibc
 151 See
 152 .BR crypt (3).
 153 .SS Features in glibc
 154 In glibc 2.2, these functions use the DES algorithm.
 155 .SH EXAMPLE
 156 .EX
 157 #define _XOPEN_SOURCE
 158 #include <stdio.h>
 159 #include <stdlib.h>
 160 #include <unistd.h>
 161 #include <crypt.h>
 162
 163 int
 164 main(void)
 165 {
 166     char key[64];
 167     char orig[9] = "eggplant";
 168     char buf[64];
 169     char txt[9];
 170     int i, j;
 171
 172     for (i = 0; i < 64; i++) {
 173         key[i] = rand() & 1;
 174     }
 175
 176     for (i = 0; i < 8; i++) {
 177         for (j = 0; j < 8; j++) {
 178             buf[i * 8 + j] = orig[i] >> j & 1;
 179         }
 180         setkey(key);
 181     }
 182     printf("Before encrypting: %s\\n", orig);
 183
 184     encrypt(buf, 0);
 185     for (i = 0; i < 8; i++) {
 186         for (j = 0, txt[i] = \(aq\\0\(aq; j < 8; j++) {
 187             txt[i] |= buf[i * 8 + j] << j;
 188         }
 189         txt[8] = \(aq\\0\(aq;
 190     }
 191     printf("After encrypting:  %s\\n", txt);
 192
 193     encrypt(buf, 1);
 194     for (i = 0; i < 8; i++) {
 195         for (j = 0, txt[i] = \(aq\\0\(aq; j < 8; j++) {
 196             txt[i] |= buf[i * 8 + j] << j;
 197         }
 198         txt[8] = \(aq\\0\(aq;
 199     }
 200     printf("After decrypting:  %s\\n", txt);
 201     exit(EXIT_SUCCESS);
 202 }
 203 .EE
 204 .SH SEE ALSO
 205 .BR cbc_crypt (3),
 206 .BR crypt (3),
 207 .BR ecb_crypt (3),
 208 .\" .BR fcrypt (3)