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arcfour style

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This commit is contained in:
Mirek Kratochvil 2012-12-16 15:36:00 +01:00
parent 9001f8531f
commit bbb8765a62
1 changed files with 30 additions and 29 deletions
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59
src/arcfour.h
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@ -21,57 +21,58 @@
#include <vector> #include <vector>
template<class inttype> class arcfour { template<class inttype> class arcfour
{
std::vector<inttype> S; std::vector<inttype> S;
inttype I,J; inttype I, J;
size_t mod; size_t mod;
public: public:
bool init(size_t bits) { bool init (size_t bits) {
if(bits>8*sizeof(inttype)) return false; if (bits > 8 * sizeof (inttype) ) return false;
I=J=0; I = J = 0;
S.resize(1<<bits); S.resize (1 << bits);
mod=1<<bits; mod = 1 << bits;
for(size_t i=0;i<(1<<bits);++i) { for (size_t i = 0; i < (1 << bits); ++i) {
S[i]=i; S[i] = i;
} }
return true; return true;
} }
void clear() { void clear() {
I=J=0; I = J = 0;
mod=0; mod = 0;
S.clear(); S.clear();
} }
void load_key(const std::vector<inttype>&K) { void load_key (const std::vector<inttype>&K) {
inttype j=0,t; inttype j = 0, t;
for(size_t i=0;i<mod;++i) { for (size_t i = 0; i < mod; ++i) {
j=(j+S[i]+K[i%K.size()])%mod; j = (j + S[i] + K[i % K.size()]) % mod;
t=S[j]; t = S[j];
S[j]=S[i]; S[j] = S[i];
S[i]=t; S[i] = t;
} }
} }
inttype gen() { inttype gen() {
I=(I+1)%mod; I = (I + 1) % mod;
J=(J+S[I])%mod; J = (J + S[I]) % mod;
register inttype t; register inttype t;
t=S[J]; t = S[J];
S[J]=S[I]; S[J] = S[I];
S[I]=t; S[I] = t;
return S[(S[I]+S[J])%mod]; return S[ (S[I] + S[J]) % mod];
} }
void discard(size_t n) { void discard (size_t n) {
for(size_t i=0;i<n;++i) gen(); for (size_t i = 0; i < n; ++i) gen();
} }
void gen(size_t n, std::vector<inttype>&out) { void gen (size_t n, std::vector<inttype>&out) {
out.resize(n); out.resize (n);
for(size_t i=0;i<n;++i) out[i]=gen(); for (size_t i = 0; i < n; ++i) out[i] = gen();
} }
}; };