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 <string.h>
  16 #include <des.h>
  17 #include "des_internal.h"
  18
  19 /*
  20  * The following are the weak DES keys:
  21  */
  22 static const des_cblock weak[16] = {
  23     /* weak keys */
  24     {0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01},
  25     {0xfe,0xfe,0xfe,0xfe,0xfe,0xfe,0xfe,0xfe},
  26     {0x1f,0x1f,0x1f,0x1f,0x0e,0x0e,0x0e,0x0e},
  27     {0xe0,0xe0,0xe0,0xe0,0xf1,0xf1,0xf1,0xf1},
  28
  29     /* semi-weak */
  30     {0x01,0xfe,0x01,0xfe,0x01,0xfe,0x01,0xfe},
  31     {0xfe,0x01,0xfe,0x01,0xfe,0x01,0xfe,0x01},
  32
  33     {0x1f,0xe0,0x1f,0xe0,0x0e,0xf1,0x0e,0xf1},
  34     {0xe0,0x1f,0xe0,0x1f,0xf1,0x0e,0xf1,0x0e},
  35
  36     {0x01,0xe0,0x01,0xe0,0x01,0xf1,0x01,0xf1},
  37     {0xe0,0x01,0xe0,0x01,0xf1,0x01,0xf1,0x01},
  38
  39     {0x1f,0xfe,0x1f,0xfe,0x0e,0xfe,0x0e,0xfe},
  40     {0xfe,0x1f,0xfe,0x1f,0xfe,0x0e,0xfe,0x0e},
  41
  42     {0x01,0x1f,0x01,0x1f,0x01,0x0e,0x01,0x0e},
  43     {0x1f,0x01,0x1f,0x01,0x0e,0x01,0x0e,0x01},
  44
  45     {0xe0,0xfe,0xe0,0xfe,0xf1,0xfe,0xf1,0xfe},
  46     {0xfe,0xe0,0xfe,0xe0,0xfe,0xf1,0xfe,0xf1}
  47 };
  48
  49 /*
  50  * des_is_weak_key: returns true iff key is a [semi-]weak des key.
  51  *
  52  * Requires: key has correct odd parity.
  53  */
  54 int
  55 des_is_weak_key(key)
  56      des_cblock key;
  57 {
  58     int i;
  59     const des_cblock *weak_p = weak;
  60
  61     for (i = 0; i < (sizeof(weak)/sizeof(des_cblock)); i++) {
  62         if (!bcmp((char *)weak_p++,(char *)key,sizeof(des_cblock)))
  63             return 1;
  64     }
  65
  66     return 0;
  67 }