1.1 --- a/src/bootstrap.c	Sun Jan 31 18:28:24 2010 +1000
     1.2 +++ b/src/bootstrap.c	Wed Feb 10 18:16:19 2010 +1000
     1.3 @@ -135,3 +135,71 @@
     1.4          INFO( buf, NULL );
     1.5      }
     1.6  }
     1.7 +
     1.8 +/* Scramble/unscramble, based on Marcus Comstedt's algorithm. */
     1.9 +
    1.10 +typedef uint16_t randseed;
    1.11 +
    1.12 +#define MAXBLOCK (2048*1024)
    1.13 +#define CHUNKSIZE 32
    1.14 +#define NEXT(seed)  (((seed = (seed*2109+9273)&0x7fff) + 0xC000) & 0xFFFF)
    1.15 +
    1.16 +void bootprogram_scramble( unsigned char *dest, unsigned char *src, size_t length )
    1.17 +{
    1.18 +    randseed seed = length & 0xFFFF;
    1.19 +    unsigned table[MAXBLOCK/32];
    1.20 +    unsigned char *s = src;
    1.21 +    unsigned char *d = dest;
    1.22 +
    1.23 +    for( unsigned blocksize = MAXBLOCK; blocksize >= CHUNKSIZE; blocksize >>= 1 ) {
    1.24 +        while( length >= blocksize ) {
    1.25 +            unsigned nchunks = blocksize/CHUNKSIZE;
    1.26 +            for( unsigned i=0; i<nchunks; i++ ) {
    1.27 +                table[i] = i; // Identity
    1.28 +            }
    1.29 +            for( unsigned i = nchunks-1; i != (unsigned)-1; --i ) {
    1.30 +                unsigned j = (NEXT(seed) * i)>>16;
    1.31 +                unsigned tmp = table[i];
    1.32 +                table[i] = table[j];
    1.33 +                table[j] = tmp;
    1.34 +                memcpy( d, s + CHUNKSIZE*table[i], CHUNKSIZE );
    1.35 +                d+= CHUNKSIZE;
    1.36 +            }
    1.37 +            length -= blocksize;
    1.38 +            s += blocksize;
    1.39 +        }
    1.40 +    }
    1.41 +    if( length ) {
    1.42 +        memcpy( d, s, length );
    1.43 +    }
    1.44 +}
    1.45 +
    1.46 +void bootprogram_unscramble( unsigned char *dest, unsigned char *src, size_t length )
    1.47 +{
    1.48 +    randseed seed = length & 0xFFFF;
    1.49 +    unsigned table[MAXBLOCK/32];
    1.50 +    unsigned char *s = src;
    1.51 +    unsigned char *d = dest;
    1.52 +
    1.53 +    for( unsigned blocksize = MAXBLOCK; blocksize >= CHUNKSIZE; blocksize >>= 1 ) {
    1.54 +        while( length >= blocksize ) {
    1.55 +            unsigned nchunks = blocksize/CHUNKSIZE;
    1.56 +            for( unsigned i=0; i<nchunks; i++ ) {
    1.57 +                table[i] = i; // Identity
    1.58 +            }
    1.59 +            for( unsigned i = nchunks-1; i != (unsigned)-1; --i ) {
    1.60 +                unsigned j = (NEXT(seed) * i)>>16;
    1.61 +                unsigned tmp = table[i];
    1.62 +                table[i] = table[j];
    1.63 +                table[j] = tmp;
    1.64 +                memcpy( d + CHUNKSIZE*table[i], s, CHUNKSIZE );
    1.65 +                s+= CHUNKSIZE;
    1.66 +            }
    1.67 +            length -= blocksize;
    1.68 +            d += blocksize;
    1.69 +        }
    1.70 +    }
    1.71 +    if( length ) {
    1.72 +        memcpy( d, s, length );
    1.73 +    }
    1.74 +}