1 /* 2 * These routines check and fix parity of encryption keys for the DES 3 * algorithm. 4 * 5 * They are a replacement for routines in key_parity.c, that don't require 6 * the table building that they do. 7 * 8 * Mark Eichin -- Cygnus Support 9 */ 10 11 12 #include "des_int.h" 13 14 /* 15 * des_fixup_key_parity: Forces odd parity per byte; parity is bits 16 * 8,16,...64 in des order, implies 0, 8, 16, ... 17 * vax order. 18 */ 19 #define smask(step) ((1<<step)-1) 20 #define pstep(x,step) (((x)&smask(step))^(((x)>>step)&smask(step))) 21 #define parity_char(x) pstep(pstep(pstep((x),4),2),1) 22 23 void 24 mit_des_fixup_key_parity(mit_des_cblock key) 25 { 26 int i; 27 for (i=0; i<sizeof(mit_des_cblock); i++) 28 { 29 key[i] &= 0xfe; 30 key[i] |= 1^parity_char(key[i]); 31 } 32 33 return; 34 } 35 36 /* 37 * des_check_key_parity: returns true iff key has the correct des parity. 38 * See des_fix_key_parity for the definition of 39 * correct des parity. 40 */ 41 int 42 mit_des_check_key_parity(mit_des_cblock key) 43 { 44 int i; 45 46 for (i=0; i<sizeof(mit_des_cblock); i++) 47 { 48 if((key[i] & 1) == parity_char(0xfe&key[i])) 49 { 50 return 0; 51 } 52 } 53 54 return(1); 55 } 56 57