src/des/weak_key.c

   1 /*
   2  * Copyright 1989 by the Massachusetts Institute of Technology.
   3  *
   4  * For copying and distribution information, please see the file
   5  * <mit-copyright.h>.
   6  *
   7  * Under U.S. law, this software may not be exported outside the US
   8  * without license from the U.S. Commerce department.
   9  *
  10  * These routines form the library interface to the DES facilities.
  11  *
  12  * Originally written 8/85 by Steve Miller, MIT Project Athena.
  13  */
  14
  15 #include <des.h>
  16 #include "des_internal.h"
  17
  18 /*
  19  * The following are the weak DES keys:
  20  */
  21 static const des_cblock weak[16] = {
  22     /* weak keys */
  23     {0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01},
  24     {0xfe,0xfe,0xfe,0xfe,0xfe,0xfe,0xfe,0xfe},
  25     {0x1f,0x1f,0x1f,0x1f,0x0e,0x0e,0x0e,0x0e},
  26     {0xe0,0xe0,0xe0,0xe0,0xf1,0xf1,0xf1,0xf1},
  27
  28     /* semi-weak */
  29     {0x01,0xfe,0x01,0xfe,0x01,0xfe,0x01,0xfe},
  30     {0xfe,0x01,0xfe,0x01,0xfe,0x01,0xfe,0x01},
  31
  32     {0x1f,0xe0,0x1f,0xe0,0x0e,0xf1,0x0e,0xf1},
  33     {0xe0,0x1f,0xe0,0x1f,0xf1,0x0e,0xf1,0x0e},
  34
  35     {0x01,0xe0,0x01,0xe0,0x01,0xf1,0x01,0xf1},
  36     {0xe0,0x01,0xe0,0x01,0xf1,0x01,0xf1,0x01},
  37
  38     {0x1f,0xfe,0x1f,0xfe,0x0e,0xfe,0x0e,0xfe},
  39     {0xfe,0x1f,0xfe,0x1f,0xfe,0x0e,0xfe,0x0e},
  40
  41     {0x01,0x1f,0x01,0x1f,0x01,0x0e,0x01,0x0e},
  42     {0x1f,0x01,0x1f,0x01,0x0e,0x01,0x0e,0x01},
  43
  44     {0xe0,0xfe,0xe0,0xfe,0xf1,0xfe,0xf1,0xfe},
  45     {0xfe,0xe0,0xfe,0xe0,0xfe,0xf1,0xfe,0xf1}
  46 };
  47
  48 /*
  49  * des_is_weak_key: returns true iff key is a [semi-]weak des key.
  50  *
  51  * Requires: key has correct odd parity.
  52  */
  53 int
  54 des_is_weak_key(key)
  55      des_cblock key;
  56 {
  57     int i;
  58     const des_cblock *weak_p = weak;
  59
  60     for (i = 0; i < (sizeof(weak)/sizeof(des_cblock)); i++) {
  61         if (!bcmp((char *)weak_p++,(char *)key,sizeof(des_cblock)))
  62             return 1;
  63     }
  64
  65     return 0;
  66 }