\Encryption
seal-2.c
```/* SEAL */

#define ALG_OK 0
#define ALG_NOTOK 1
#define WORDS_PER_SEAL_CALL 1024

typedef struct {
unsigned long t[520]; /* 512 rounded up to a multiple of 5 + 5*/
unsigned long s[265]; /* 256 rounded up to a multiple of 5 + 5*/
unsigned long r[20]; /* 16 rounded up to multiple of 5 */
unsigned long counter; /* 32-bit synch value. */
unsigned long ks_buf[WORDS_PER_SEAL_CALL];
int ks_pos;
} seal_ctx;

#define ROT2(x) (((x) >>2) | ((x) << 30))
#define ROT8(x) (((x) >>8) | ((x) << 24))
#define ROT9(x) (((x) >>9) | ((x) << 23))
#define ROT16(x) (((x) >> 16) | ((x) << 16))
#define ROT24(x) (((x) >> 24) | ((x) << 8))
#define ROT27(x) (((x) >> 27) | ((x) << 5))

#define WORD(cp) ((cp[0]<<24)|(cp[1]<<16)|(cp[2]<<8)|(cp[3]))

#define F1(x, y, z) (((x) & (y)) | ((~(x)) & (z)))
#define F2(x, y, z) ((x) ^ (y) ^ (z))
#define F3(x, y, z) (((x) & (y)) | ((x) & (z)) | ((y) & (z)))
#define F4(x, y, z) ((x) ^ (y) ^ (z))

int g(in,i,h)
unsigned char *in;
int i;
unsigned long *h;
{

unsigned long h0,h1,h2,h3,h4,a,b,c,d,e,temp;
unsigned char *kp;
unsigned long w[80];

kp = in;
h0 = WORD(kp); kp += 4;
h1 = WORD(kp); kp += 4;
h2 = WORD(kp); kp += 4;
h3 = WORD(kp); kp += 4;
h4 = WORD(kp); kp += 4;

w[0] = i;
for (i=1;i<16;i++) w[i] = 0;

for (i=16;i<80;i++) w[i] = w[i-3]^w[i-8]^w[i-14]^w[i-16];

a = h0; b = h1; c = h2; d = h3; e = h4;

for(i=0;i<20;i++) {
temp = ROT27(a) + F1(b, c, d) + e + w[i] + 0x5a827999;
e = d; d = c; c = ROT2(b); b = a; a = temp;
}

for (i=20;i<40;i++) {
temp = ROT27(a) + F2(b, c, d) + e + w[i] + 0x6ed9eba1;
e = d; d = c; c = ROT2(b); b = a; a = temp;
}
for (i=40;i<60;i++) {
temp = ROT27(a) + F3(b, c, d) + e + w[i] + 0x8f1bbcdc;
e = d; d = c; c = ROT2(b); b = a; a = temp;
}
for (i=60;i<80;i++) {
temp = ROT27(a) + F4(b, c, d) + e + w[i] + 0xca62c1d6;
e = d; d = c; c = ROT2(b); b = a; a = temp;
}

h[0] = h0+a; h[1] = h1+b; h[2] = h2+c; h[3] = h3+d; h[4] = h4+e;

return (ALG_OK);
}

unsigned long gamma (a,i)
unsigned char *a;
int i;
{
unsigned long h[5];

(void) g(a, i/5, h);
return h[i % 5];
}

int seal_init( seal_ctx *result, unsigned char *key )
{
int i;
unsigned long h[5];

for (i=0;i<510;i+=5)
g(key, i/5, &(result->t[i]));
/* horrible special case for the end */
g(key, 510/5, h);
for(i=510;i<512;i++)
result->t[i] = h[i-510];
/* 0x1000 mod 5 is +1, so have horrible special case for the start */
g(key, (-1+0x1000)/5, h);
for (i=0;i<4;i++)
result->s[i] = h[i+1];
for (i=4;i<254;i+=5)
g(key, (i+0x1000)/5, &(result->s[i]));
/* horrible special case for the end */
g(key, (254+0x1000)/5, h);
for (i=254;i<256;i++)
result->s[i] = h[i-254];
/* 0x2000 mod 5 is +2, so have horrible special case at the start */
g(key, (-2+0x2000)/5, h);
for(i=0;i<3;i++)
result->r[i] = h[i+2];
for (i=3;i<13;i+=5)
g(key,(i+0x2000)/5,&(result->r[i]));
/* horrible special case for the end */
g(key, (13+0x2000)/5, h);
for (i=13;i<16;i++)
result->r[i] = h[i-13];
return (ALG_OK);
}

int seal(seal_ctx *key, unsigned long in, unsigned long *out)
{
int i,j,l;
unsigned long a,b,c,d,n1,n2,n3,n4,*wp;
unsigned short p,q;

wp = out;
for (l=0;l<4;l++) {
a = in ^ key->r[4*l];
b = ROT8(in) ^ key->r[4*l+1];
c = ROT16(in) ^ key->r[4*l+2];
d = ROT24(in) ^ key->r[4*l+3];
}

for (j=0;j<2;j++) {
p= a & 0x7fc;
b += key->t[p/4];
a = ROT9(a);

p = b & 0x7fc;
c += key->t[p/4];
b = ROT9(b);

p = c & 0x7fc;
d += key->t[p/4];
c = ROT9(c);

p = d & 0x7fc;
a += key->t[p/4];
d = ROT9(d);

n1 = d; n2=b; n3=a; n4=c;

p = a & 0x7fc;
b += key->t[p/4];
a = ROT9(a);

p = b & 0x7fc;
c += key->t[p/4];
b = ROT9(b);

p = c & 0x7fc;
d += key->t[p/4];
c = ROT9(c);

p = d & 0x7fc;
a += key->t[p/4];
d = ROT9(d);

/* This generates 64 32-bit words, or 256 bytes of keystream. */
for (i=0;i<64;i++) {

p = a & 0x7fc;
b += key->t[p/4];
a = ROT9(a);
b ^= a;

q = b & 0x7fc;
c ^= key->t[q/4];
b = ROT9(b);
c += b;

p = (p+c) & 0x7fc;
d += key->t[p/4];
c = ROT9(c);
d ^= c;

q = (q+d) & 0x7fc;
a ^= key->t[q/4];
d = ROT9(d);
a += d;

p = (p+a) & 0x7fc;
b ^= key->t[p/4];
a = ROT9(a);

q = (q+b) & 0x7fc;
c += key->t[q/4];
b = ROT9(b);

p = (p+c) & 0x7fc;
d ^= key->t[p/4];
c = ROT9(c);

q = (q+d) & 0x7fc;
a += key->t[q/4];
d = ROT9(d);

*wp = b + key->s[4*i]; wp++;
*wp = c ^ key->s[4*i+1]; wp++;
*wp = d + key->s[4*i+2]; wp++;
*wp = a ^ key->s[4*i+3]; wp++;

if(i&1) {
a += n3;
c += n4;
} else {
a += n1;
c += n2;
}
}
}
return (ALG_OK);
}

/* Added call to refill ks_buf and reset counter and ks_pos. */
void seal_refill_buffer(seal_ctx *c){
seal(c,c->counter,c->ks_buf);
c->counter++;
c->ks_pos = 0;
}

void seal_key(seal_ctx *c, unsigned char *key){
seal_init(c,key);
c->counter = 0; /* By default, init to zero. */
c->ks_pos = WORDS_PER_SEAL_CALL;
/* Refill keystream buffer on next call. */
}

/* This encrypts the next w words with SEAL. */
void seal_encrypt(seal_ctx *c, unsigned long *data_ptr, int w){
int i;

for(i=0;iks_pos>=WORDS_PER_SEAL_CALL) seal_refill_buffer(c);
data_ptr[i]^=c->ks_buf[c->ks_pos];
c->ks_pos++;
}
}

void seal_decrypt(seal_ctx *c, unsigned long *data_ptr, int w) {
seal_encrypt(c,data_ptr,w);
}

void seal_resynch(seal_ctx *c, unsigned long synch_word){
c->counter = synch_word;
c->ks_pos = WORDS_PER_SEAL_CALL;
}

void main(void){
seal_ctx sc;
unsigned long buf[1000],t;
int i,flag;
unsigned char key[] = { 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19 };

printf("1\n");
seal_key(&sc,key);

printf("2\n");
for(i=0;i<1000;i++) buf[i]=0;

printf("3\n");
seal_encrypt(&sc,buf,1000);

printf("4\n");
t = 0;

for(i=0;i<1000;i++) t = t ^ buf[i];
printf("XOR of buf is %08lx.\n",t);

seal_key(&sc,key);
seal_decrypt(&sc,buf,1);
seal_decrypt(&sc,buf+1,999);

flag = 0;
for(i=0;i<1000;i++) if(buf[i]!=0)flag=1;
if(flag) printf("Decrypt failed.\n");
else printf("Decrypt succeeded.\n");
}
```