wbrawner/openssl
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

RC4 tune-up.

Browse source 
See comments in the code (after #if defined(RC4_CHUNK)) for more details.
This commit is contained in:
Andy Polyakov 1999-09-26 12:47:17 +00:00
parent 8569c322be
commit 6cc4ee03df
1 changed files with 98 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

98
crypto/rc4/rc4_enc.c
View 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;
}