diff options
Diffstat (limited to 'src/lib/crypto/krb/nfold.c')
| -rw-r--r-- | src/lib/crypto/krb/nfold.c | 99 |
1 files changed, 50 insertions, 49 deletions
diff --git a/src/lib/crypto/krb/nfold.c b/src/lib/crypto/krb/nfold.c index 976e131af6..11082accac 100644 --- a/src/lib/crypto/krb/nfold.c +++ b/src/lib/crypto/krb/nfold.c @@ -1,3 +1,4 @@ +/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */ /* * Copyright (C) 1998 by the FundsXpress, INC. * @@ -30,24 +31,24 @@ #endif /* -n-fold(k-bits): - l = lcm(n,k) - r = l/k - s = k-bits | k-bits rot 13 | k-bits rot 13*2 | ... | k-bits rot 13*(r-1) - compute the 1's complement sum: - n-fold = s[0..n-1]+s[n..2n-1]+s[2n..3n-1]+..+s[(k-1)*n..k*n-1] -*/ + * n-fold(k-bits): + * l = lcm(n,k) + * r = l/k + * s = k-bits | k-bits rot 13 | k-bits rot 13*2 | ... | k-bits rot 13*(r-1) + * compute the 1's complement sum: + * n-fold = s[0..n-1]+s[n..2n-1]+s[2n..3n-1]+..+s[(k-1)*n..k*n-1] + */ /* representation: msb first, assume n and k are multiples of 8, and - that k>=16. this is the case of all the cryptosystems which are - likely to be used. this function can be replaced if that - assumption ever fails. */ + * that k>=16. this is the case of all the cryptosystems which are + * likely to be used. this function can be replaced if that + * assumption ever fails. */ /* input length is in bits */ void krb5int_nfold(unsigned int inbits, const unsigned char *in, unsigned int outbits, - unsigned char *out) + unsigned char *out) { int a,b,c,lcm; int byte, i, msbit; @@ -64,9 +65,9 @@ krb5int_nfold(unsigned int inbits, const unsigned char *in, unsigned int outbits b = inbits; while(b != 0) { - c = b; - b = a%b; - a = c; + c = b; + b = a%b; + a = c; } lcm = outbits*inbits/a; @@ -79,51 +80,51 @@ krb5int_nfold(unsigned int inbits, const unsigned char *in, unsigned int outbits /* this will end up cycling through k lcm(k,n)/k times, which is correct */ for (i=lcm-1; i>=0; i--) { - /* compute the msbit in k which gets added into this byte */ - msbit = (/* first, start with the msbit in the first, unrotated - byte */ - ((inbits<<3)-1) - /* then, for each byte, shift to the right for each - repetition */ - +(((inbits<<3)+13)*(i/inbits)) - /* last, pick out the correct byte within that - shifted repetition */ - +((inbits-(i%inbits))<<3) - )%(inbits<<3); - - /* pull out the byte value itself */ - byte += (((in[((inbits-1)-(msbit>>3))%inbits]<<8)| - (in[((inbits)-(msbit>>3))%inbits])) - >>((msbit&7)+1))&0xff; - - /* do the addition */ - byte += out[i%outbits]; - out[i%outbits] = byte&0xff; + /* compute the msbit in k which gets added into this byte */ + msbit = (/* first, start with the msbit in the first, unrotated + byte */ + ((inbits<<3)-1) + /* then, for each byte, shift to the right for each + repetition */ + +(((inbits<<3)+13)*(i/inbits)) + /* last, pick out the correct byte within that + shifted repetition */ + +((inbits-(i%inbits))<<3) + )%(inbits<<3); + + /* pull out the byte value itself */ + byte += (((in[((inbits-1)-(msbit>>3))%inbits]<<8)| + (in[((inbits)-(msbit>>3))%inbits])) + >>((msbit&7)+1))&0xff; + + /* do the addition */ + byte += out[i%outbits]; + out[i%outbits] = byte&0xff; #if 0 - printf("msbit[%d] = %d\tbyte = %02x\tsum = %03x\n", i, msbit, - (((in[((inbits-1)-(msbit>>3))%inbits]<<8)| - (in[((inbits)-(msbit>>3))%inbits])) - >>((msbit&7)+1))&0xff, byte); + printf("msbit[%d] = %d\tbyte = %02x\tsum = %03x\n", i, msbit, + (((in[((inbits-1)-(msbit>>3))%inbits]<<8)| + (in[((inbits)-(msbit>>3))%inbits])) + >>((msbit&7)+1))&0xff, byte); #endif - /* keep around the carry bit, if any */ - byte >>= 8; + /* keep around the carry bit, if any */ + byte >>= 8; #if 0 - printf("carry=%d\n", byte); + printf("carry=%d\n", byte); #endif } /* if there's a carry bit left over, add it back in */ if (byte) { - for (i=outbits-1; i>=0; i--) { - /* do the addition */ - byte += out[i]; - out[i] = byte&0xff; - - /* keep around the carry bit, if any */ - byte >>= 8; - } + for (i=outbits-1; i>=0; i--) { + /* do the addition */ + byte += out[i]; + out[i] = byte&0xff; + + /* keep around the carry bit, if any */ + byte >>= 8; + } } } |