man3/encrypt.3

   1 .\" Copyright 2000 Nicolás Lichtmaier <nick@debian.org>
   2 .\" Created 2000-07-22 00:52-0300
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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
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  24 .TH ENCRYPT 3 2003-04-04 "glibc2" "Cryptographic Functions"
  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 ", struct crypt_data *" data );
  47 .sp
  48 Each of these requires linking with
  49 .BR -lcrypt .
  50 .SH DESCRIPTION
  51 These functions encrypt and decrypt 64-bit messages. The
  52 .B setkey()
  53 function sets the key used by
  54 .BR encrypt() .
  55 The
  56 .I key
  57 parameter used here is an array of 64 bytes, each of which has
  58 numerical value 1 or 0. The bytes key[n] where n=8*i-1 are ignored,
  59 so that the effective key length is 56 bits.
  60 .PP
  61 The encrypt() function modifies the passed buffer, encoding if
  62 .I edflag
  63 is 0, and decoding if 1 is being passed. Like the key parameter also
  64 .I block
  65 is a bit vector representation of the actual value that is encoded.
  66 The result is returned in that same vector.
  67 .PP
  68 These two functions are not reentrant, that is, the key data is
  69 kept in static storage. The functions
  70 .B setkey_r()
  71 and
  72 .B encrypt_r()
  73 are the reentrant versions. They use the following
  74 structure to hold the key data:
  75 .RS
  76 .nf
  77 struct crypt_data {
  78       char keysched[16 * 8];
  79       char sb0[32768];
  80       char sb1[32768];
  81       char sb2[32768];
  82       char sb3[32768];
  83       char crypt_3_buf[14];
  84       char current_salt[2];
  85       long int current_saltbits;
  86       int  direction, initialized;
  87 };
  88 .fi
  89 .RE
  90 Before calling
  91 .B setkey_r()
  92 set
  93 .I data->initialized
  94 to zero.
  95 .SH "RETURN VALUE"
  96 These functions do not return any value.
  97 .SH ERRORS
  98 Set
  99 .I errno
 100 to zero before calling the above functions.
 101 On success, it is unchanged.
 102 .TP
 103 .BR ENOSYS
 104 The function is not provided.
 105 (For example because of former USA export restrictions.)
 106 .SH EXAMPLE
 107 You need to link with libcrypt to compile this example with glibc2.2.
 108 To do useful work the key[] and txt[] array must be filled with a
 109 useful bit pattern. Note that the <crypt.h> header unconditionally
 110 gives the prototypes for setkey() and encrypt().
 111 .sp
 112 .nf
 113 #include <crypt.h>
 114
 115 main() {
 116   char key[64];      /* bit pattern for key */
 117   char txt[64];      /* bit pattern for messages */
 118   setkey(key);
 119   encrypt(txt, 0);   /* encode */
 120   encrypt(txt, 1);   /* decode */
 121 }
 122 .fi
 123 .SH "NOTE"
 124 In glibc2.2 these functions use the DES algorithm.
 125 .SH "CONFORMING TO"
 126 The functions
 127 .B encrypt()
 128 and
 129 .B setkey()
 130 conform to SVID, SUSv2, and POSIX 1003.1-2001.
 131 The functions
 132 .B encrypt_r()
 133 and
 134 .B setkey_r()
 135 are GNU extensions.
 136 .SH "SEE ALSO"
 137 .BR cbc_crypt (3),
 138 .BR crypt (3),
 139 .BR ecb_crypt (3),
 140 .BR fcrypt (3)