man3/encrypt.3

   1 .\" Copyright 2000 Nicolás Lichtmaier <nick@debian.org>
   2 .\" Created 2000-07-22 00:52-0300
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   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 .BI "#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
  50 .BR \-lcrypt .
  51 .SH DESCRIPTION
  52 These functions encrypt and decrypt 64-bit messages.
  53 The
  54 .BR setkey ()
  55 function sets the key used by
  56 .BR encrypt ().
  57 The
  58 .I key
  59 parameter used here is an array of 64 bytes, each of which has
  60 numerical value 1 or 0.
  61 The bytes key[n] where n=8*i-1 are ignored,
  62 so that the effective key length is 56 bits.
  63 .PP
  64 The
  65 .BR encrypt ()
  66 function modifies the passed buffer, encoding if
  67 .I edflag
  68 is 0, and decoding if 1 is being passed.
  69 Like the key parameter also
  70 .I block
  71 is a bit vector representation of the actual value that is encoded.
  72 The result is returned in that same vector.
  73 .PP
  74 These two functions are not reentrant, that is, the key data is
  75 kept in static storage.
  76 The functions
  77 .BR setkey_r ()
  78 and
  79 .BR encrypt_r ()
  80 are the reentrant versions.
  81 They use the following
  82 structure to hold the key data:
  83 .RS
  84 .nf
  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 .RE
  99 Before calling
 100 .BR setkey_r ()
 101 set
 102 .I data->initialized
 103 to zero.
 104 .SH "RETURN VALUE"
 105 These functions do not return any value.
 106 .SH ERRORS
 107 Set
 108 .I errno
 109 to zero before calling the above functions.
 110 On success, it is unchanged.
 111 .TP
 112 .BR ENOSYS
 113 The function is not provided.
 114 (For example because of former USA export restrictions.)
 115 .SH EXAMPLE
 116 You need to link with libcrypt to compile this example with glibc 2.2.
 117 To do useful work the key[] and txt[] arrays must be filled with a
 118 useful bit pattern.
 119 .sp
 120 .nf
 121 #define _XOPEN_SOURCE
 122 #include <unistd.h>
 123 #include <stdlib.h>
 124
 125 int
 126 main(void)
 127 {
 128     char key[64];      /* bit pattern for key */
 129     char txt[64];      /* bit pattern for messages */
 130
 131     setkey(key);
 132     encrypt(txt, 0);   /* encode */
 133     encrypt(txt, 1);   /* decode */
 134 }
 135 .fi
 136 .SH NOTES
 137 In glibc 2.2 these functions use the DES algorithm.
 138 .SH "CONFORMING TO"
 139 The functions
 140 .BR encrypt ()
 141 and
 142 .BR setkey ()
 143 conform to SVr4, SUSv2, and POSIX.1-2001.
 144 The functions
 145 .BR encrypt_r ()
 146 and
 147 .BR setkey_r ()
 148 are GNU extensions.
 149 .SH "SEE ALSO"
 150 .BR cbc_crypt (3),
 151 .BR crypt (3),
 152 .BR ecb_crypt (3),
 153 .BR fcrypt (3),
 154 .BR feature_test_macros (7)