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Diffstat (limited to 'libdes/f_tables.h')
| -rw-r--r-- | libdes/f_tables.h | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/libdes/f_tables.h b/libdes/f_tables.h new file mode 100644 index 0000000..db9cbb9 --- /dev/null +++ b/libdes/f_tables.h @@ -0,0 +1,223 @@ +/* + * Copyright (c) 1990 Dennis Ferguson. All rights reserved. + * + * Commercial use is permitted only if products which are derived from + * or include this software are made available for purchase and/or use + * in Canada. Otherwise, redistribution and use in source and binary + * forms are permitted. + */ + +/* + * des_tables.h - declarations to import the DES tables, used internally + * by some of the library routines. + */ +#ifndef __DES_TABLES_H__ +#define __DES_TABLES_H__ /* nothing */ + +/* + * These may be declared const if you wish. Be sure to change the + * declarations in des_tables.c as well. + */ +extern unsigned long des_IP_table[256]; +extern unsigned long des_FP_table[256]; +extern unsigned long des_SP_table[8][64]; + +/* + * Use standard shortforms to reference these to save typing + */ +#define IP des_IP_table +#define FP des_FP_table +#define SP des_SP_table + +/* + * Code to do a DES round using the tables. Note that the E expansion + * is easy to compute algorithmically, especially if done out-of-order. + * Take a look at its form and compare it to everything involving temp + * below. Since SP[0-7] don't have any bits in common set it is okay + * to do the successive xor's. + * + * Note too that the SP table has been reordered to match the order of + * the keys (if the original order of SP was 12345678, the reordered + * table is 71354682). This is unnecessary, but was done since some + * compilers seem to like you going through the matrix from beginning + * to end. + * + * There is a difference in the best way to do this depending on whether + * one is encrypting or decrypting. If encrypting we move forward through + * the keys and hence should move forward through the table. If decrypting + * we go back. Part of the need for this comes from trying to emulate + * existing software which generates a single key schedule and uses it + * both for encrypting and decrypting. Generating separate encryption + * and decryption key schedules would allow one to use the same code + * for both. + * + * left, right and temp should be unsigned long values. left and right + * should be the high and low order parts of the cipher block at the + * current stage of processing (this makes sense if you read the spec). + * kp should be an unsigned long pointer which points at the current + * set of subkeys in the key schedule. It is advanced to the next set + * (i.e. by 8 bytes) when this is done. + * + * This occurs in the innermost loop of the DES function. The four + * variables should really be in registers. + * + * When using this, the inner loop of the DES function might look like: + * + * for (i = 0; i < 8; i++) { + * DES_SP_{EN,DE}CRYPT_ROUND(left, right, temp, kp); + * DES_SP_{EN,DE}CRYPT_ROUND(right, left, temp, kp); + * } + * + * Note the trick above. You are supposed to do 16 rounds, swapping + * left and right at the end of each round. By doing two rounds at + * a time and swapping left and right in the code we can avoid the + * swaps altogether. + */ +#define DES_SP_ENCRYPT_ROUND(left, right, temp, kp) \ + (temp) = (((right) >> 11) | ((right) << 21)) ^ *(kp)++; \ + (left) ^= SP[0][((temp) >> 24) & 0x3f] \ + | SP[1][((temp) >> 16) & 0x3f] \ + | SP[2][((temp) >> 8) & 0x3f] \ + | SP[3][((temp) ) & 0x3f]; \ + (temp) = (((right) >> 23) | ((right) << 9)) ^ *(kp)++; \ + (left) ^= SP[4][((temp) >> 24) & 0x3f] \ + | SP[5][((temp) >> 16) & 0x3f] \ + | SP[6][((temp) >> 8) & 0x3f] \ + | SP[7][((temp) ) & 0x3f] + +#define DES_SP_DECRYPT_ROUND(left, right, temp, kp) \ + (temp) = (((right) >> 23) | ((right) << 9)) ^ *(--(kp)); \ + (left) ^= SP[7][((temp) ) & 0x3f] \ + | SP[6][((temp) >> 8) & 0x3f] \ + | SP[5][((temp) >> 16) & 0x3f] \ + | SP[4][((temp) >> 24) & 0x3f]; \ + (temp) = (((right) >> 11) | ((right) << 21)) ^ *(--(kp)); \ + (left) ^= SP[3][((temp) ) & 0x3f] \ + | SP[2][((temp) >> 8) & 0x3f] \ + | SP[1][((temp) >> 16) & 0x3f] \ + | SP[0][((temp) >> 24) & 0x3f] + +/* + * Macros to help deal with the initial permutation table. Note + * the IP table only deals with 32 bits at a time, allowing us to + * collect the bits we need to deal with each half into an unsigned + * long. By carefully selecting how the bits are ordered we also + * take advantages of symmetries in the table so that we can use a + * single table to compute the permutation of all bytes. This sounds + * complicated, but if you go through the process of designing the + * table you'll find the symmetries fall right out. + * + * The follow macros compute the set of bits used to index the + * table for produce the left and right permuted result. + */ +#define DES_IP_LEFT_BITS(left, right) \ + ((((left) & 0x55555555) << 1) | ((right) & 0x55555555)) +#define DES_IP_RIGHT_BITS(left, right) \ + (((left) & 0xaaaaaaaa) | (((right) & 0xaaaaaaaa) >> 1)) + +/* + * The following macro does an in-place initial permutation given + * the current left and right parts of the block and a single + * temporary. Use this more as a guide for rolling your own, though. + * The best way to do the IP depends on the form of the data you + * are dealing with. If you use this, though, try to make left, + * right and temp register unsigned longs. + */ +#define DES_INITIAL_PERM(left, right, temp) \ + (temp) = DES_IP_RIGHT_BITS((left), (right)); \ + (right) = DES_IP_LEFT_BITS((left), (right)); \ + (left) = IP[((right) >> 24) & 0xff] \ + | (IP[((right) >> 16) & 0xff] << 1) \ + | (IP[((right) >> 8) & 0xff] << 2) \ + | (IP[(right) & 0xff] << 3); \ + (right) = IP[((temp) >> 24) & 0xff] \ + | (IP[((temp) >> 16) & 0xff] << 1) \ + | (IP[((temp) >> 8) & 0xff] << 2) \ + | (IP[(temp) & 0xff] << 3) + + +/* + * Now the final permutation stuff. The same comments apply to + * this as to the initial permutation, except that we use different + * bits and shifts. + */ +#define DES_FP_LEFT_BITS(left, right) \ + ((((left) & 0x0f0f0f0f) << 4) | ((right) & 0x0f0f0f0f)) +#define DES_FP_RIGHT_BITS(left, right) \ + (((left) & 0xf0f0f0f0) | (((right) & 0xf0f0f0f0) >> 4)) + + +/* + * Here is a sample final permutation. Note that there is a trick + * here. DES requires swapping the left and right parts after the + * last cipher round but before the final permutation. We do this + * swapping internally, which is why left and right are confused + * at the beginning. + */ +#define DES_FINAL_PERM(left, right, temp) \ + (temp) = DES_FP_RIGHT_BITS((right), (left)); \ + (right) = DES_FP_LEFT_BITS((right), (left)); \ + (left) = (FP[((right) >> 24) & 0xff] << 6) \ + | (FP[((right) >> 16) & 0xff] << 4) \ + | (FP[((right) >> 8) & 0xff] << 2) \ + | FP[(right) & 0xff]; \ + (right) = (FP[((temp) >> 24) & 0xff] << 6) \ + | (FP[((temp) >> 16) & 0xff] << 4) \ + | (FP[((temp) >> 8) & 0xff] << 2) \ + | FP[temp & 0xff] + + +/* + * Finally, as a sample of how all this might be held together, the + * following two macros do in-place encryptions and decryptions. left + * and right are two unsigned long variables which at the beginning + * are expected to hold the clear (encrypted) block in host byte order + * (left the high order four bytes, right the low order). At the end + * they will contain the encrypted (clear) block. temp is an unsigned long + * used as a temporary. kp is an unsigned long pointer pointing at + * the start of the key schedule. All these should be in registers. + * + * You can probably do better than these by rewriting for particular + * situations. These aren't bad, though. + */ +#define DES_DO_ENCRYPT(left, right, temp, kp) \ + do { \ + register int i; \ + DES_INITIAL_PERM((left), (right), (temp)); \ + for (i = 0; i < 8; i++) { \ + DES_SP_ENCRYPT_ROUND((left), (right), (temp), (kp)); \ + DES_SP_ENCRYPT_ROUND((right), (left), (temp), (kp)); \ + } \ + DES_FINAL_PERM((left), (right), (temp)); \ + (kp) -= (2 * 16); \ + } while (0) + +#define DES_DO_DECRYPT(left, right, temp, kp) \ + do { \ + register int i; \ + DES_INITIAL_PERM((left), (right), (temp)); \ + (kp) += (2 * 16); \ + for (i = 0; i < 8; i++) { \ + DES_SP_DECRYPT_ROUND((left), (right), (temp), (kp)); \ + DES_SP_DECRYPT_ROUND((right), (left), (temp), (kp)); \ + } \ + DES_FINAL_PERM((left), (right), (temp)); \ + } while (0) + +/* + * These are handy dandy utility thingies for straightening out bytes. + * Included here because they're used a couple of places. + */ +#define GET_HALF_BLOCK(lr, ip) \ + (lr) = ((u_int32)(*(ip)++)) << 24; \ + (lr) |= ((u_int32)(*(ip)++)) << 16; \ + (lr) |= ((u_int32)(*(ip)++)) << 8; \ + (lr) |= (u_int32)(*(ip)++) + +#define PUT_HALF_BLOCK(lr, op) \ + *(op)++ = ((lr) >> 24) & 0xff; \ + *(op)++ = ((lr) >> 16) & 0xff; \ + *(op)++ = ((lr) >> 8) & 0xff; \ + *(op)++ = (lr) & 0xff + +#endif /* __DES_TABLES_H__ */ |