Some loss in speed, but a great space savings.
---
crypto/des_generic.c | 72 +++++++++-----------------------------------------
1 files changed, 13 insertions(+), 59 deletions(-)
diff --git a/crypto/des_generic.c b/crypto/des_generic.c
index 656039b..baf51cf 100644
--- a/crypto/des_generic.c
+++ b/crypto/des_generic.c
@@ -667,68 +667,22 @@ EXPORT_SYMBOL_GPL(des_ekey);
*
* No weak key checking is performed, as this is only used by triple DES
*
+ * Since the decryption round keys are just the encryption round keys in
+ * reverse order, this just generates the encryption key and reverses it.
+ * A special-purpose function would be faster, but it would waste a lot of
+ * space.
*/
sstatic void des_dkey(u32 pe[DES_EXPKEY_WORDS], const u8 k[DES_KEY_SIZE])
{
- /* K&R: long is at least 32 bits */
- unsigned long a, b, c, d;
- const u32 *pt = pc2;
-
- d = pc1[ ((k[4] & 0x0e) << 4) + (k[0] & 0x1e) ];
- c = pc1[ ((k[5] & 0x0e) << 4) + (k[1] & 0x1e) ];
- b = pc1[ ((k[6] & 0x0e) << 4) + (k[2] & 0x1e) ];
- a = pc1[ ((k[7] & 0x0e) << 4) + (k[3] & 0x1e) ];
-
- pe[ 0 * 2] = PC2(pt, a, b, c, d); d = rs[d];
- pe[ 1 * 2] = PC2(pt, d, a, b, c); c = rs[c]; b = rs[b];
- pe[ 2 * 2] = PC2(pt, b, c, d, a); a = rs[a]; d = rs[d];
- pe[ 3 * 2] = PC2(pt, d, a, b, c); c = rs[c]; b = rs[b];
- pe[ 4 * 2] = PC2(pt, b, c, d, a); a = rs[a]; d = rs[d];
- pe[ 5 * 2] = PC2(pt, d, a, b, c); c = rs[c]; b = rs[b];
- pe[ 6 * 2] = PC2(pt, b, c, d, a); a = rs[a]; d = rs[d];
- pe[ 7 * 2] = PC2(pt, d, a, b, c); c = rs[c];
- pe[ 8 * 2] = PC2(pt, c, d, a, b); b = rs[b]; a = rs[a];
- pe[ 9 * 2] = PC2(pt, a, b, c, d); d = rs[d]; c = rs[c];
- pe[10 * 2] = PC2(pt, c, d, a, b); b = rs[b]; a = rs[a];
- pe[11 * 2] = PC2(pt, a, b, c, d); d = rs[d]; c = rs[c];
- pe[12 * 2] = PC2(pt, c, d, a, b); b = rs[b]; a = rs[a];
- pe[13 * 2] = PC2(pt, a, b, c, d); d = rs[d]; c = rs[c];
- pe[14 * 2] = PC2(pt, c, d, a, b); b = rs[b];
- pe[15 * 2] = PC2(pt, b, c, d, a);
-
- /* Skip to next table set */
- pt += 512;
-
- d = pc1[ ((k[0] & 0xe0) >> 4) + (k[4] & 0xf0) + 1 ];
- c = pc1[ ((k[1] & 0xe0) >> 4) + (k[5] & 0xf0) + 1 ];
- b = pc1[ ((k[2] & 0xe0) >> 4) + (k[6] & 0xf0) + 1 ];
- a = pc1[ ((k[3] & 0xe0) >> 4) + (k[7] & 0xf0) + 1 ];
-
- pe[ 0 * 2 + 1] = PC2(pt, a, b, c, d); d = rs[d];
- pe[ 1 * 2 + 1] = PC2(pt, d, a, b, c); c = rs[c]; b = rs[b];
- pe[ 2 * 2 + 1] = PC2(pt, b, c, d, a); a = rs[a]; d = rs[d];
- pe[ 3 * 2 + 1] = PC2(pt, d, a, b, c); c = rs[c]; b = rs[b];
- pe[ 4 * 2 + 1] = PC2(pt, b, c, d, a); a = rs[a]; d = rs[d];
- pe[ 5 * 2 + 1] = PC2(pt, d, a, b, c); c = rs[c]; b = rs[b];
- pe[ 6 * 2 + 1] = PC2(pt, b, c, d, a); a = rs[a]; d = rs[d];
- pe[ 7 * 2 + 1] = PC2(pt, d, a, b, c); c = rs[c];
- pe[ 8 * 2 + 1] = PC2(pt, c, d, a, b); b = rs[b]; a = rs[a];
- pe[ 9 * 2 + 1] = PC2(pt, a, b, c, d); d = rs[d]; c = rs[c];
- pe[10 * 2 + 1] = PC2(pt, c, d, a, b); b = rs[b]; a = rs[a];
- pe[11 * 2 + 1] = PC2(pt, a, b, c, d); d = rs[d]; c = rs[c];
- pe[12 * 2 + 1] = PC2(pt, c, d, a, b); b = rs[b]; a = rs[a];
- pe[13 * 2 + 1] = PC2(pt, a, b, c, d); d = rs[d]; c = rs[c];
- pe[14 * 2 + 1] = PC2(pt, c, d, a, b); b = rs[b];
- pe[15 * 2 + 1] = PC2(pt, b, c, d, a);
+ int i;
- /* Fixup: 2413 5768 -> 1357 2468 */
- for (d = 0; d < 16; ++d) {
- a = pe[2 * d];
- b = pe[2 * d + 1];
- MASKSWAP(a, b, c, 0xffff0000);
- ROL(b, 18);
- pe[2 * d] = a;
- pe[2 * d + 1] = b;
+ des_ekey(pe, k)
+ /* Swap 0<->30, 1<->31, 2<->28, 3<->29, 4<->26,... 14<->16, 15<->17 */
+ for (i = 0; i < 16; i++) {
+ int j = 0x1e ^ i;
+ u32 t = pe[i];
+ pe[i] = pe[j];
+ pe[j] = t;
}
}
--
1.6.0.6
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