// encryption: data must be NUL-padded to BLOCKSIZE
// decryption: data must be padded to BLOCKSIZE
// len must be < 2^31
void SymmCipher::ctr_crypt(byte* data, unsigned len, m_off_t pos, ctr_iv ctriv, byte* mac, bool encrypt, bool initmac)
{
assert(!(pos & (KEYLENGTH - 1)));
byte ctr[BLOCKSIZE], tmp[BLOCKSIZE];
MemAccess::set<int64_t>(ctr,ctriv);
setint64(pos / BLOCKSIZE, ctr + sizeof ctriv);
if (mac && initmac)
{
memcpy(mac, ctr, sizeof ctriv);
memcpy(mac + sizeof ctriv, ctr, sizeof ctriv);
}
while ((int)len > 0)
{
if (encrypt)
{
if(mac)
{
xorblock(data, mac);
ecb_encrypt(mac);
}
ecb_encrypt(ctr, tmp);
xorblock(tmp, data);
}
else
{
ecb_encrypt(ctr, tmp);
xorblock(tmp, data);
if (mac)
{
if (len >= (unsigned)BLOCKSIZE)
{
xorblock(data, mac);
}
else
{
xorblock(data, mac, len);
}
ecb_encrypt(mac);
}
}
len -= BLOCKSIZE;
data += BLOCKSIZE;
incblock(ctr);
}
}
// encryption: data must be NUL-padded to BLOCKSIZE
// decryption: data must be padded to BLOCKSIZE
// len must be < 2^31
void SymmCipher::ctr_crypt(byte* data, unsigned len, m_off_t pos, ctr_iv ctriv, byte* mac, int encrypt)
{
assert(!(pos&(KEYLENGTH-1)));
byte ctr[BLOCKSIZE], tmp[BLOCKSIZE];
*(uint64_t*)ctr = ctriv;
setint64(pos/BLOCKSIZE,ctr+sizeof ctriv);
memcpy(mac,ctr,sizeof ctriv);
memcpy(mac+sizeof ctriv,ctr,sizeof ctriv);
while ((int)len > 0)
{
if (encrypt)
{
xorblock(data,mac);
ecb_encrypt(mac);
ecb_encrypt(ctr,tmp);
xorblock(tmp,data);
}
else
{
ecb_encrypt(ctr,tmp);
xorblock(tmp,data);
if (len >= (unsigned)BLOCKSIZE) xorblock(data,mac);
else xorblock(data,mac,len);
ecb_encrypt(mac);
}
len -= BLOCKSIZE;
data += BLOCKSIZE;
incblock(ctr);
}
}