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Applied Cryptography: Protocols, Algorithms and Source Code in C, 20th Anniversary Edition by Bruce Schneier

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PART V

SOURCE CODE

DES

#define END   0      /* MODE == encrypt */
#define DEl   1      /* MODE == decrypt */

typedef struct {
        unsigned long ek[32];
        unsigned long dk[32];
} des_ctx;

extern void deskey(unsigned char *, short);
/*                  hexkey[8]     MODE
 * Sets the internal key register according to the hexadecimal
 * key contained in the 8 bytes of hexkey, according to the DES,
 * for encryption or decryption according to MODE.
 */

extern void usekey(unsigned long *);
/*                cookedkey[32]
* Loads the internal key register with the data in cookedkey. */ extern void cpkey(unsigned long *); /* cookedkey[32] * Copies the contents of the internal key register into the storage * located at &cookedkey[0]. */ extern void des(unsigned char *, unsigned char *); /* from[8] to[8] * Encrypts/Decrypts (according to the key currently loaded in the * internal key register) one block of eight bytes at address 'from' * into the block at address 'to'. They can be the same. */ static void scrunch(unsigned char *, unsigned long *); static void unscrun(unsigned long *, unsigned char *); static void desfunc(unsigned long *, unsigned long *); static void cookey(unsigned long *); static unsigned long KnL[32] = { 0L }; static unsigned long KnR[32] = { 0L }; static unsigned long Kn3[32] = { 0L }; static unsigned char Df_Key[24] = { 0x01,0x23,0x45,0x67,0x89,0xab,0xcd,0xef, 0xfe,0xdc,0xba,0x98,0x76,0x54,0x32,0x10, 0x89,0xab,0xcd,0xef,0x01,0x23,0x45,0x67 }; static ...

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