man3/encrypt.3

   1 .\" Copyright 2000 Nicolás Lichtmaier <nick@debian.org>
   2 .\" Created 2000-07-22 00:52-0300
   3 .\"
   4 .\" This is free documentation; you can redistribute it and/or
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  19 .\" Modified 2002-07-23 19:21:35 CEST 2002 Walter Harms
  20 .\" <walter.harms@informatik.uni-oldenburg.de>
  21 .\"
  22 .\" Modified 2003-04-04, aeb
  23 .\"
  24 .TH ENCRYPT 3 2003-04-04 "" "Linux Programmer's Manual"
  25 .SH NAME
  26 encrypt, setkey, encrypt_r, setkey_r \- encrypt 64-bit messages
  27 .SH SYNOPSIS
  28 .B #define _XOPEN_SOURCE
  29 .br
  30 .B #include <unistd.h>
  31 .sp
  32 .BI "void encrypt(char " block "[64], int " edflag );
  33 .sp
  34 .B #define _XOPEN_SOURCE
  35 .br
  36 .B #include <stdlib.h>
  37 .sp
  38 .BI "void setkey(const char *" key );
  39 .sp
  40 .B #define _GNU_SOURCE
  41 .br
  42 .B "#include <crypt.h>"
  43 .sp
  44 .BI "void setkey_r(const char *" key ", struct crypt_data *" data );
  45 .br
  46 .BI "void encrypt_r(char *" block ", int " edflag \
  47 ", struct crypt_data *" data );
  48 .sp
  49 Each of these requires linking with \fI\-lcrypt\fP.
  50 .SH DESCRIPTION
  51 These functions encrypt and decrypt 64-bit messages.
  52 The
  53 .BR setkey ()
  54 function sets the key used by
  55 .BR encrypt ().
  56 The
  57 .I key
  58 parameter used here is an array of 64 bytes, each of which has
  59 numerical value 1 or 0.
  60 The bytes key[n] where n=8*i-1 are ignored,
  61 so that the effective key length is 56 bits.
  62 .PP
  63 The
  64 .BR encrypt ()
  65 function modifies the passed buffer, encoding if
  66 .I edflag
  67 is 0, and decoding if 1 is being passed.
  68 Like the key parameter also
  69 .I block
  70 is a bit vector representation of the actual value that is encoded.
  71 The result is returned in that same vector.
  72 .PP
  73 These two functions are not reentrant, that is, the key data is
  74 kept in static storage.
  75 The functions
  76 .BR setkey_r ()
  77 and
  78 .BR encrypt_r ()
  79 are the reentrant versions.
  80 They use the following
  81 structure to hold the key data:
  82 .in +4n
  83 .nf
  84
  85 struct crypt_data {
  86     char     keysched[16 * 8];
  87     char     sb0[32768];
  88     char     sb1[32768];
  89     char     sb2[32768];
  90     char     sb3[32768];
  91     char     crypt_3_buf[14];
  92     char     current_salt[2];
  93     long int current_saltbits;
  94     int      direction;
  95     int      initialized;
  96 };
  97 .fi
  98 .in
  99 .PP
 100 Before calling
 101 .BR setkey_r ()
 102 set
 103 .I data->initialized
 104 to zero.
 105 .SH "RETURN VALUE"
 106 These functions do not return any value.
 107 .SH ERRORS
 108 Set
 109 .I errno
 110 to zero before calling the above functions.
 111 On success, it is unchanged.
 112 .TP
 113 .B ENOSYS
 114 The function is not provided.
 115 (For example because of former USA export restrictions.)
 116 .SH "CONFORMING TO"
 117 The functions
 118 .BR encrypt ()
 119 and
 120 .BR setkey ()
 121 conform to SVr4, SUSv2, and POSIX.1-2001.
 122 The functions
 123 .BR encrypt_r ()
 124 and
 125 .BR setkey_r ()
 126 are GNU extensions.
 127 .SH NOTES
 128 In glibc 2.2 these functions use the DES algorithm.
 129 .SH EXAMPLE
 130 You need to link with libcrypt to compile this example with glibc 2.2.
 131 To do useful work the
 132 .I key[]
 133 and
 134 .I txt[]
 135 arrays must be filled with a useful bit pattern.
 136 .sp
 137 .nf
 138 #define _XOPEN_SOURCE
 139 #include <unistd.h>
 140 #include <stdlib.h>
 141
 142 int
 143 main(void)
 144 {
 145     char key[64];      /* bit pattern for key */
 146     char txt[64];      /* bit pattern for messages */
 147
 148     setkey(key);
 149     encrypt(txt, 0);   /* encode */
 150     encrypt(txt, 1);   /* decode */
 151 }
 152 .fi
 153 .SH "SEE ALSO"
 154 .BR cbc_crypt (3),
 155 .BR crypt (3),
 156 .BR ecb_crypt (3),
 157 .\" .BR fcrypt (3),
 158 .BR feature_test_macros (7)