/*
* Function: ECRYPT_ivsetup
*
* Synopsis
* Load the key and perform initial clockings.
*
* Assumptions
* The key is 10 bytes and the IV is 8 bytes. The
* registers are loaded in the following way:
*
* NFSR[0] = lsb of key[0]
* ...
* NFSR[7] = msb of key[0]
* ...
* ...
* NFSR[72] = lsb of key[9]
* ...
* NFSR[79] = msb of key[9]
* LFSR[0] = lsb of IV[0]
* ...
* LFSR[7] = msb of IV[0]
* ...
* ...
* LFSR[56] = lsb of IV[7]
* ...
* LFSR[63] = msb of IV[7]
*/
void ECRYPT_ivsetup(
ECRYPT_ctx* ctx,
const u8* iv)
{
u32 i,j;
u8 outbit;
/* load registers */
for (i=0;i<(ctx->ivsize)/8;++i) {
for (j=0;j<8;++j) {
ctx->NFSR[i*8+j]=((ctx->p_key[i]>>j)&1);
ctx->LFSR[i*8+j]=((iv[i]>>j)&1);
}
}
for (i=(ctx->ivsize)/8;i<(ctx->keysize)/8;++i) {
for (j=0;j<8;++j) {
ctx->NFSR[i*8+j]=((ctx->p_key[i]>>j)&1);
ctx->LFSR[i*8+j]=1;
}
}
/* do initial clockings */
for (i=0;i<INITCLOCKS;++i) {
outbit=grain_keystream(ctx);
ctx->LFSR[79]^=outbit;
ctx->NFSR[79]^=outbit;
}
}
/*
* Function: ECRYPT_ivsetup
*
* Synopsis
* Load the key and perform initial clockings.
*
* Assumptions
* The key is 10 bytes and the IV is 8 bytes.
*
*/
void ECRYPT_ivsetup(
ECRYPT_ctx* ctx,
const u8* iv)
{
u32 outbit;
int i;
u8 *b=(u8*)ctx->b;
u8 *s=(u8*)ctx->s;
for(i=0;i<10;i++)
b[i]=ctx->p_key[i];
for(i=0;i<ctx->ivsize/8;i++)
s[i]=iv[i];
for(i=ctx->ivsize/8;i<10;i++)
s[i]=0xff;
/* do initial clockings */
for (i=0;i<INITCLOCKS;++i) {
outbit=grain_keystream(ctx);
xor79(S,outbit);
xor79(B,outbit);
}
//print_ctx(ctx);
}
/*
* Function: ECRYPT_keystream_bytes
*
* Synopsis
* Generate keystream in bytes.
*
* Assumptions
* Bits are generated in order z0,z1,z2,...
* The bits are stored in a byte in order:
*
* lsb of keystream[0] = z0
* ...
* msb of keystream[0] = z7
* ...
* lsb of keystream[1] = z8
* ...
* msb of keystream[1] = z15
* ...
* ...
* ...
* Example: The bit keystream: 10011100 10110011 ..
* corresponds to the byte keystream: 39 cd ..
*/
void ECRYPT_keystream_bytes(
ECRYPT_ctx* ctx,
u8* keystream,
u32 msglen)
{
u32 i,j;
for (i = 0; i < msglen; ++i) {
keystream[i]=0;
for (j = 0; j < 8; ++j) {
keystream[i]|=(grain_keystream(ctx)<<j);
}
}
}
void ECRYPT_decrypt_bytes(
ECRYPT_ctx* ctx,
const u8* ciphertext,
u8* plaintext,
u32 msglen)
{
u32 i,j;
u8 k=0;
for (i = 0; i < msglen; ++i) {
k=0;
for (j = 0; j < 8; ++j) {
k|=(grain_keystream(ctx)<<j);
}
plaintext[i]=ciphertext[i]^k;
}
}