idea.cpp
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// idea.cpp - written and placed in the public domain by Wei Dai
#include "pch.h"
#include "idea.h"
#include "misc.h"
NAMESPACE_BEGIN(CryptoPP)
static const int IDEA_KEYLEN=(6*IDEA::ROUNDS+4); // key schedule length in # of word16s
#define low16(x) ((x)&0xffff) // compiler should be able to optimize this away if word is 16 bits
#define high16(x) ((x)>>16)
CRYPTOPP_COMPILE_ASSERT(sizeof(IDEA::Word) >= 2);
// should use an inline function but macros are still faster in MSVC 4.0
#define DirectMUL(a,b) \
{ \
assert(b <= 0xffff); \
\
word32 p=(word32)low16(a)*b; \
\
if (p) \
{ \
p = low16(p) - high16(p); \
a = (IDEA::Word)p - (IDEA::Word)high16(p); \
} \
else \
a = 1-a-b; \
}
#ifdef IDEA_LARGECACHE
volatile bool IDEA::Base::tablesBuilt = false;
word16 IDEA::Base::log[0x10000];
word16 IDEA::Base::antilog[0x10000];
void IDEA::Base::BuildLogTables()
{
if (tablesBuilt)
return;
else
{
tablesBuilt = true;
IDEA::Word x=1;
word32 i;
for (i=0; i<0x10000; i++)
{
antilog[i] = (word16)x;
DirectMUL(x, 3);
}
for (i=0; i<0x10000; i++)
log[antilog[i]] = (word16)i;
}
}
void IDEA::Base::LookupKeyLogs()
{
IDEA::Word* Z=key;
int r=ROUNDS;
do
{
Z[0] = log[Z[0]];
Z[3] = log[Z[3]];
Z[4] = log[Z[4]];
Z[5] = log[Z[5]];
Z+=6;
} while (--r);
Z[0] = log[Z[0]];
Z[3] = log[Z[3]];
}
inline void IDEA::Base::LookupMUL(IDEA::Word &a, IDEA::Word b)
{
a = antilog[low16(log[low16(a)]+b)];
}
#endif // IDEA_LARGECACHE
void IDEA::Base::UncheckedSetKey(const byte *userKey, unsigned int length, const NameValuePairs &)
{
AssertValidKeyLength(length);
#ifdef IDEA_LARGECACHE
BuildLogTables();
#endif
EnKey(userKey);
if (!IsForwardTransformation())
DeKey();
#ifdef IDEA_LARGECACHE
LookupKeyLogs();
#endif
}
void IDEA::Base::EnKey (const byte *userKey)
{
unsigned int i;
for (i=0; i<8; i++)
m_key[i] = ((IDEA::Word)userKey[2*i]<<8) | userKey[2*i+1];
for (; i<IDEA_KEYLEN; i++)
{
unsigned int j = RoundDownToMultipleOf(i,8U)-8;
m_key[i] = low16((m_key[j+(i+1)%8] << 9) | (m_key[j+(i+2)%8] >> 7));
}
}
static IDEA::Word MulInv(IDEA::Word x)
{
IDEA::Word y=x;
for (unsigned i=0; i<15; i++)
{
DirectMUL(y,low16(y));
DirectMUL(y,x);
}
return low16(y);
}
static inline IDEA::Word AddInv(IDEA::Word x)
{
return low16(0-x);
}
void IDEA::Base::DeKey()
{
FixedSizeSecBlock<IDEA::Word, 6*ROUNDS+4> tempkey;
size_t i;
for (i=0; i<ROUNDS; i++)
{
tempkey[i*6+0] = MulInv(m_key[(ROUNDS-i)*6+0]);
tempkey[i*6+1] = AddInv(m_key[(ROUNDS-i)*6+1+(i>0)]);
tempkey[i*6+2] = AddInv(m_key[(ROUNDS-i)*6+2-(i>0)]);
tempkey[i*6+3] = MulInv(m_key[(ROUNDS-i)*6+3]);
tempkey[i*6+4] = m_key[(ROUNDS-1-i)*6+4];
tempkey[i*6+5] = m_key[(ROUNDS-1-i)*6+5];
}
tempkey[i*6+0] = MulInv(m_key[(ROUNDS-i)*6+0]);
tempkey[i*6+1] = AddInv(m_key[(ROUNDS-i)*6+1]);
tempkey[i*6+2] = AddInv(m_key[(ROUNDS-i)*6+2]);
tempkey[i*6+3] = MulInv(m_key[(ROUNDS-i)*6+3]);
m_key = tempkey;
}
#ifdef IDEA_LARGECACHE
#define MUL(a,b) LookupMUL(a,b)
#else
#define MUL(a,b) DirectMUL(a,b)
#endif
void IDEA::Base::ProcessAndXorBlock(const byte *inBlock, const byte *xorBlock, byte *outBlock) const
{
typedef BlockGetAndPut<word16, BigEndian> Block;
const IDEA::Word *key = m_key;
IDEA::Word x0,x1,x2,x3,t0,t1;
Block::Get(inBlock)(x0)(x1)(x2)(x3);
for (unsigned int i=0; i<ROUNDS; i++)
{
MUL(x0, key[i*6+0]);
x1 += key[i*6+1];
x2 += key[i*6+2];
MUL(x3, key[i*6+3]);
t0 = x0^x2;
MUL(t0, key[i*6+4]);
t1 = t0 + (x1^x3);
MUL(t1, key[i*6+5]);
t0 += t1;
x0 ^= t1;
x3 ^= t0;
t0 ^= x1;
x1 = x2^t1;
x2 = t0;
}
MUL(x0, key[ROUNDS*6+0]);
x2 += key[ROUNDS*6+1];
x1 += key[ROUNDS*6+2];
MUL(x3, key[ROUNDS*6+3]);
Block::Put(xorBlock, outBlock)(x0)(x2)(x1)(x3);
}
NAMESPACE_END