RC4 tune-up.
authorAndy Polyakov <appro@openssl.org>
Sun, 26 Sep 1999 12:47:17 +0000 (12:47 +0000)
committerAndy Polyakov <appro@openssl.org>
Sun, 26 Sep 1999 12:47:17 +0000 (12:47 +0000)
See comments in the code (after #if defined(RC4_CHUNK)) for more details.

crypto/rc4/rc4_enc.c

index 3256bea..93a75cd 100644 (file)
@@ -78,6 +78,103 @@ void RC4(RC4_KEY *key, unsigned long len, unsigned char *indata,
         y=key->y;     
         d=key->data; 
 
+#if defined(RC4_CHUNK) && (defined(L_ENDIAN) || defined(B_ENDIAN))
+       /*
+        * The original reason for implementing this(*) was the fact that
+        * pre-21164a Alpha CPUs don't have byte load/store instructions
+        * and e.g. a byte store has to be done with 64-bit load, shift,
+        * and, or and finally 64-bit store. Peaking data and operating
+        * at natural word size made it possible to reduce amount of
+        * instructions as well as to perform early read-ahead without
+        * suffering from RAW (read-after-write) hazard. This resulted
+        * in >40%(**) performance improvement (on 21064 box with gcc).
+        * But it's not only Alpha users who win here:-) Thanks to the
+        * early-n-wide read-ahead this implementation also exhibits
+        * >40% speed-up on SPARC and almost 20% on MIPS.
+        *
+        * (*)  "this" means code which recognizes the case when input
+        *      and output pointers appear to be aligned at natural CPU
+        *      word boundary.
+        * (**) i.e. according to 'apps/openssl speed rc4' benchmark,
+        *      crypto/rc4/rc4speed.c exhibits almost 70% speed-up.
+        *
+        *                                      <appro@fy.chalmers.se>
+        */
+
+#define RC4_STEP       ( \
+                       x=(x+1) &0xff,  \
+                       tx=d[x],        \
+                       y=(tx+y)&0xff,  \
+                       ty=d[y],        \
+                       d[y]=tx,        \
+                       d[x]=ty,        \
+                       (RC4_CHUNK)d[(tx+ty)&0xff]\
+                       )
+
+#if defined(L_ENDIAN)
+#  define SHFT(c)      ((c)*8)
+#  define MASK(i)      (((RC4_CHUNK)-1)>>((sizeof(RC4_CHUNK)-(i))<<3))
+#  define SHINC                8
+#elif defined(B_ENDIAN)
+#  define SHFT(c)      ((sizeof(RC4_CHUNK)-(c)-1)*8)
+#  define MASK(i)      (((RC4_CHUNK)-1)<<((sizeof(RC4_CHUNK)-(i))<<3))
+#  define SHINC                -8
+#else
+#  error "L_ENDIAN or B_ENDIAN *must* be defined!"
+#endif
+
+       if ( ( ((unsigned long)indata  & (sizeof(RC4_CHUNK)-1)) | 
+              ((unsigned long)outdata & (sizeof(RC4_CHUNK)-1)) ) == 0
+          ) {
+               RC4_CHUNK ichunk,cipher;
+
+               for (;len&-sizeof(RC4_CHUNK);len-=sizeof(RC4_CHUNK)) {
+                       ichunk  = *(RC4_CHUNK *)indata;
+                       cipher  = RC4_STEP<<SHFT(0);
+                       cipher |= RC4_STEP<<SHFT(1);
+                       cipher |= RC4_STEP<<SHFT(2);
+                       cipher |= RC4_STEP<<SHFT(3);
+#ifdef RC4_CHUNK_IS_64_BIT
+                       cipher |= RC4_STEP<<SHFT(4);
+                       cipher |= RC4_STEP<<SHFT(5);
+                       cipher |= RC4_STEP<<SHFT(6);
+                       cipher |= RC4_STEP<<SHFT(7);
+#endif
+                       *(RC4_CHUNK *)outdata = cipher^ichunk;
+                       indata  += sizeof(RC4_CHUNK);
+                       outdata += sizeof(RC4_CHUNK);
+               }
+               if (len) {
+                       RC4_CHUNK mask,ochunk;
+
+                       ichunk = *(RC4_CHUNK *)indata;
+                       ochunk = *(RC4_CHUNK *)outdata;
+                       cipher = 0;
+                       i = SHFT(0);
+                       mask = MASK(len);
+                       switch (len) {
+#ifdef RC4_CHUNK_IS_64_BIT
+                               case 7: cipher  = RC4_STEP<<SHFT(0), i+=SHINC;
+                               case 6: cipher |= RC4_STEP<<i,  i+=SHINC;
+                               case 5: cipher |= RC4_STEP<<i,  i+=SHINC;
+                               case 4: cipher |= RC4_STEP<<i,  i+=SHINC;
+                               case 3: cipher |= RC4_STEP<<i,  i+=SHINC;
+#else
+                               case 3: cipher  = RC4_STEP<<SHFT(0), i+=SHINC;
+#endif
+                               case 2: cipher |= RC4_STEP<<i,  i+=SHINC;
+                               case 1: cipher |= RC4_STEP<<i,  i+=SHINC;
+                               case 0: ; /* it's never the case, but it
+                                            has to be here for ultrix? */
+                       }
+                       ochunk &= ~mask;
+                       ochunk |= (cipher^ichunk) & mask;
+                       *(RC4_CHUNK *)outdata = ochunk;
+               }
+       }
+       else
+#endif
+       {
 #define LOOP(in,out) \
                x=((x+1)&0xff); \
                tx=d[x]; \
@@ -126,6 +223,7 @@ void RC4(RC4_KEY *key, unsigned long len, unsigned char *indata,
                        RC4_LOOP(indata,outdata,6); if (--i == 0) break;
                        }
                }               
+       }
        key->x=x;     
        key->y=y;
        }