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CHG: some textual change to README.txt

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ADD: a prng.c to collect some different PRNG's i've ran into
ADD: some changes the tea implementation
ADD: a enhanced version - SwapEndian64ex
This commit is contained in:
iceman1001 2015-12-21 19:48:00 +01:00
commit f4d0ffd1b9
8 changed files with 86 additions and 37 deletions
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39
common/prng.c Normal file
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@ -0,0 +1,39 @@
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// Burtle Prng - Modified. 42iterations instead of 20.
// ref: http://burtleburtle.net/bob/rand/smallprng.html
//-----------------------------------------------------------------------------
#include "prng.h"
#define rot(x,k) (((x)<<(k))|((x)>>(32-(k))))
uint32_t burtle_get_mod( prng_ctx *x ) {
uint32_t e = x->a - rot(x->b, 21);
x->a = x->b ^ rot(x->c, 19);
x->b = x->c + rot(x->d, 6);
x->c = x->d + e;
x->d = e + x->a;
return x->d;
}
void burtle_init_mod(prng_ctx *x, uint32_t seed ) {
x->a = 0xf1ea5eed;
x->b = x->c = x->d = seed;
for (uint8_t i=0; i < 42; ++i) {
(void)burtle_get_mod(x);
}
}
void burtle_init(prng_ctx *x, uint32_t seed ) {
uint32_t i;
x->a = 0xf1ea5eed, x->b = x->c = x->d = seed;
for (i=0; i < 20; ++i) {
(void)burtle_get_mod(x);
}
}
uint32_t GetSimplePrng( uint32_t seed ){
seed *= 0x19660D;
seed += 0x3C6EF35F;
return seed;
}

24
common/prng.h Normal file
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@ -0,0 +1,24 @@
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// Burtle Prng - Modified. 42iterations instead of 20.
// ref: http://burtleburtle.net/bob/rand/smallprng.html
//-----------------------------------------------------------------------------
#ifndef __PRNG_H
#define __PRNG_H
#include <stdint.h>
#include <stddef.h>
typedef struct prng_ctx {
uint32_t a;
uint32_t b;
uint32_t c;
uint32_t d;
} prng_ctx;
//uint32_t burtle_get( prng_ctx *x );
uint32_t burtle_get_mod( prng_ctx *x );
void burtle_init_mod(prng_ctx *x, uint32_t seed );
void burtle_init(prng_ctx *x, uint32_t seed );
uint32_t GetSimplePrng( uint32_t seed );
#endif /* __PRNG_H */

22
common/tea.c
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@ -10,8 +10,6 @@
#define ROUNDS 32
#define DELTA 0x9E3779B9
#define SUM 0xC6EF3720
#define SWAPENDIAN(x)\
(x = (x >> 8 & 0xff00ff) | (x & 0xff00ff) << 8, x = x >> 16 | x << 16)
void tea_encrypt(uint8_t *v, uint8_t *key) {
@ -28,13 +26,6 @@ void tea_encrypt(uint8_t *v, uint8_t *key) {
//input
y = bytes_to_num(v, 4);
z = bytes_to_num(v+4, 4);
// SWAPENDIAN(a);
// SWAPENDIAN(b);
// SWAPENDIAN(c);
// SWAPENDIAN(d);
// SWAPENDIAN(y);
// SWAPENDIAN(z);
while ( n-- > 0 ) {
sum += DELTA;
@ -42,9 +33,6 @@ void tea_encrypt(uint8_t *v, uint8_t *key) {
z += ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
}
// SWAPENDIAN(y);
// SWAPENDIAN(z);
num_to_bytes(y, 4, v);
num_to_bytes(z, 4, v+4);
}
@ -65,22 +53,12 @@ void tea_decrypt(uint8_t *v, uint8_t *key) {
y = bytes_to_num(v, 4);
z = bytes_to_num(v+4, 4);
// SWAPENDIAN(a);
// SWAPENDIAN(b);
// SWAPENDIAN(c);
// SWAPENDIAN(d);
// SWAPENDIAN(y);
// SWAPENDIAN(z);
/* sum = delta<<5, in general sum = delta * n */
while ( n-- > 0 ) {
z -= ((y << 4) + c) ^ (y + sum) ^ ((y >> 5) + d);
y -= ((z << 4) + a) ^ (z + sum) ^ ((z >> 5) + b);
sum -= DELTA;
}
// SWAPENDIAN(y);
// SWAPENDIAN(z);
num_to_bytes(y, 4, v);
num_to_bytes(z, 4, v+4);
}