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small fixes

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This commit is contained in:
Mirek Kratochvil 2012-05-16 16:52:18 +02:00
parent b54fcb9bf3
commit 56ea9083fc
3 changed files with 24 additions and 19 deletions
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9
include/codecrypt.h
View file

@ -15,12 +15,11 @@ namespace ccr
{ {
/* /*
* typedefs. uint and sint should be able to comfortably hold the field * typedef. uint should be able to comfortably hold the field elements of
* elements of underlying calculations (esp. with polynomials. Switching to * underlying calculations (esp. with polynomials. Switching to 64bits is
* 64bits is adviseable when computing with n=64K and larger. * adviseable when computing with n=64K and larger.
*/ */
typedef unsigned int uint; typedef unsigned int uint;
typedef int sint;
/* /*
* vector over GF(2). We rely on STL's vector<bool> == bit_vector * vector over GF(2). We rely on STL's vector<bool> == bit_vector
@ -122,7 +121,7 @@ public:
uint add (uint, uint); uint add (uint, uint);
uint mult (uint, uint); uint mult (uint, uint);
uint exp (uint, sint); uint exp (uint, int);
uint inv (uint); uint inv (uint);
uint sq_root (uint); uint sq_root (uint);
}; };

31
lib/gf2m.cpp
View file

@ -9,9 +9,12 @@ using namespace ccr;
int gf2p_degree (uint p) int gf2p_degree (uint p)
{ {
int r = -1; int r = 0;
for (int i = 0; p; p >>= 1, ++i) r = i; while (p) {
return r; ++r;
p >>= 1;
}
return r - 1;
} }
inline uint gf2p_add (uint a, uint b) inline uint gf2p_add (uint a, uint b)
@ -24,7 +27,7 @@ uint gf2p_mod (uint a, uint p)
if (!p) return 0; if (!p) return 0;
int t, degp = gf2p_degree (p); int t, degp = gf2p_degree (p);
while ( (t = gf2p_degree (a) ) >= degp) { while ( (t = gf2p_degree (a) ) >= degp) {
a ^= p << (t - degp); a ^= (p << (t - degp) );
} }
return a; return a;
} }
@ -47,12 +50,12 @@ uint gf2p_modmult (uint a, uint b, uint p)
b = gf2p_mod (b, p); b = gf2p_mod (b, p);
uint r = 0; uint r = 0;
uint d = 1 << gf2p_degree (p); uint d = 1 << gf2p_degree (p);
while (a) { if (b) while (a) {
if (a & 1) r ^= b; if (a & 1) r ^= b;
a >>= 1; a >>= 1;
b <<= 1; b <<= 1;
if (b >= d) b ^= p; if (b >= d) b ^= p;
} }
return r; return r;
} }
@ -61,7 +64,7 @@ bool is_irreducible_gf2_poly (uint p)
if (!p) return false; if (!p) return false;
int d = gf2p_degree (p) / 2; int d = gf2p_degree (p) / 2;
uint test = 2; //x^1+0 uint test = 2; //x^1+0
for (int i = 0; i < d; ++i) { for (int i = 0; i <= d; ++i) {
test = gf2p_modmult (test, test, p); test = gf2p_modmult (test, test, p);
if (gf2p_gcd (test ^ 2 /* test - x^1 */, p) != 1) if (gf2p_gcd (test ^ 2 /* test - x^1 */, p) != 1)
@ -84,12 +87,16 @@ bool gf2m::create (uint M)
m = M; m = M;
n = 1 << m; n = 1 << m;
if (!n) return false; //too big. if (!n) return false; //too big.
poly = 0;
//FIXME fails for M>=12. Why?
for (uint t = (1 << m) + 1, e = 1 << (m + 1); t < e; t += 2) for (uint t = (1 << m) + 1, e = 1 << (m + 1); t < e; t += 2)
if (is_irreducible_gf2_poly (t) ) { if (is_irreducible_gf2_poly (t) ) {
poly = t; poly = t;
break; break;
} }
if (!poly) return false;
log.resize (n); log.resize (n);
antilog.resize (n); antilog.resize (n);
log[0] = n - 1; log[0] = n - 1;
@ -115,7 +122,7 @@ uint gf2m::mult (uint a, uint b)
return gf2p_tablemult (a, b, n, log, antilog); return gf2p_tablemult (a, b, n, log, antilog);
} }
uint gf2m::exp (uint a, sint k) uint gf2m::exp (uint a, int k)
{ {
if (!a) return 0; if (!a) return 0;
if (a == 1) return 1; if (a == 1) return 1;

3
lib/mce.cpp
View file

@ -15,10 +15,9 @@ int ccr::mce::generate (pubkey&pub, privkey&priv, prng&rng, uint m, uint t)
priv.g.generate_random_irreducible (t, priv.fld, rng); priv.g.generate_random_irreducible (t, priv.fld, rng);
//check and generator matrix //check and generator matrix
matrix generator;
permutation hp;
priv.g.compute_goppa_check_matrix (priv.h, priv.fld); priv.g.compute_goppa_check_matrix (priv.h, priv.fld);
matrix generator;
for (;;) if (priv.h.create_goppa_generator for (;;) if (priv.h.create_goppa_generator
(generator, priv.hperm, rng) ) break; (generator, priv.hperm, rng) ) break;