void sapphire::initialize(unsigned char *key, unsigned char keysize)
{
// Key size may be up to 256 bytes.
// Pass phrases may be used directly, with longer length
// compensating for the low entropy expected in such keys.
// Alternatively, shorter keys hashed from a pass phrase or
// generated randomly may be used. For random keys, lengths
// of from 4 to 16 bytes are recommended, depending on how
// secure you want this to be.
int i;
unsigned char toswap, swaptemp, rsum;
unsigned keypos;
// If we have been given no key, assume the default hash setup.
if (keysize < 1)
{
hash_init();
return;
}
// Start with cards all in order, one of each.
for (i=0;i<256;i++)
cards[i] = i;
// Swap the card at each position with some other card.
toswap = 0;
keypos = 0; // Start with first byte of user key.
rsum = 0;
for (i=255;i>=0;i--)
{
toswap = keyrand(i, key, keysize, &rsum, &keypos);
swaptemp = cards[i];
cards[i] = cards[toswap];
cards[toswap] = swaptemp;
}
// Initialize the indices and data dependencies.
// Indices are set to different values instead of all 0
// to reduce what is known about the state of the cards
// when the first byte is emitted.
rotor = cards[1];
ratchet = cards[3];
avalanche = cards[5];
last_plain = cards[7];
last_cipher = cards[rsum];
toswap = swaptemp = rsum = 0;
keypos = 0;
}
SapphireBase::SapphireBase(const byte *key, unsigned int keysize)
: cards(256)
{
assert(keysize < 256);
// Key size may be up to 256 bytes.
// Pass phrases may be used directly, with longer length
// compensating for the low entropy expected in such keys.
// Alternatively, shorter keys hashed from a pass phrase or
// generated randomly may be used. For random keys, lengths
// of from 4 to 16 bytes are recommended, depending on how
// secure you want this to be.
int i;
byte rsum;
unsigned keypos;
// Start with cards all in order, one of each.
for (i=0;i<256;i++)
cards[i] = i;
// Swap the card at each position with some other card.
keypos = 0; // Start with first byte of user key.
rsum = 0;
for (i=255;i;i--)
std::swap(cards[i], cards[keyrand(i, key, keysize, &rsum, &keypos)]);
// Initialize the indices and data dependencies.
// Indices are set to different values instead of all 0
// to reduce what is known about the state of the cards
// when the first byte is emitted.
rotor = cards[1];
ratchet = cards[3];
avalanche = cards[5];
last_plain = cards[7];
last_cipher = cards[rsum];
rsum = 0;
keypos = 0;
}