经过多次测试，实现了与客户端 Diffie-Hellman 密钥交换算法。
Diffie-Hellman 可以不安全的网络通道上交换密钥，详细原理见 wiki: Diffie–Hellman key exchange
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B
服务端 (alice):
> var crypto = require("crypto");
undefined
> var alice, bob, A, a, B, b, p, s1, s2;
undefined
> alice = crypto.createDiffieHellman(8);
{ _binding: {} }
> A = alice.generateKeys("hex");
'3053'
> p = alice.getPrime("hex");
'8c7b'
alice的Public Key : 0x3053 (A)，素数：0x8c7b (p)，crypto库的基础跟固定都是2(g)
客户端(bob)用polarssl库
#include <polarssl/dhm.h>
#include <polarssl/config.h>
#ifdef _MSC_VER
#include <basetsd.h>
typedef UINT32 uint32_t;
#else
#include <inttypes.h>
#endif
#include <assert.h>
/*
* 32-bit integer manipulation macros (big endian)
*/
#ifndef GET_UINT32_BE
#define GET_UINT32_BE(n,b,i) \
{ \
(n) = ( (uint32_t) (b)[(i) ] << 24 ) \
| ( (uint32_t) (b)[(i) + 1] << 16 ) \
| ( (uint32_t) (b)[(i) + 2] << 8 ) \
| ( (uint32_t) (b)[(i) + 3] ); \
}
#endif
#ifndef PUT_UINT32_BE
#define PUT_UINT32_BE(n,b,i) \
{ \
(b)[(i) ] = (unsigned char) ( (n) >> 24 ); \
(b)[(i) + 1] = (unsigned char) ( (n) >> 16 ); \
(b)[(i) + 2] = (unsigned char) ( (n) >> 8 ); \
(b)[(i) + 3] = (unsigned char) ( (n) ); \
}
#endif
int unhexify(unsigned char *obuf, const char *ibuf)
{
unsigned char c, c2;
int len = strlen(ibuf) / 2;
assert(!(strlen(ibuf) %1)); // must be even number of bytes
while (*ibuf != 0)
{
c = *ibuf++;
if( c >= '0' && c <= '9' )
c -= '0';
else if( c >= 'a' && c <= 'f' )
c -= 'a' - 10;
else if( c >= 'A' && c <= 'F' )
c -= 'A' - 10;
else
assert( 0 );
c2 = *ibuf++;
if( c2 >= '0' && c2 <= '9' )
c2 -= '0';
else if( c2 >= 'a' && c2 <= 'f' )
c2 -= 'a' - 10;
else if( c2 >= 'A' && c2 <= 'F' )
c2 -= 'A' - 10;
else
assert( 0 );
*obuf++ = ( c << 4 ) | c2;
}
return len;
}
void hexify(unsigned char *obuf, const unsigned char *ibuf, int len)
{
unsigned char l, h;
while (len != 0)
{
h = (*ibuf) / 16;
l = (*ibuf) % 16;
if( h < 10 )
*obuf++ = '0' + h;
else
*obuf++ = 'a' + h - 10;
if( l < 10 )
*obuf++ = '0' + l;
else
*obuf++ = 'a' + l - 10;
++ibuf;
len--;
}
}
/**
* This function just returns data from rand().
* Although predictable and often similar on multiple
* runs, this does not result in identical random on
* each run. So do not use this if the results of a
* test depend on the random data that is generated.
*
* rng_state shall be NULL.
*/
static int rnd_std_rand( void *rng_state, unsigned char *output, size_t len )
{
size_t i;
if( rng_state != NULL )
rng_state = NULL;
for( i = 0; i < len; ++i )
output[i] = rand();
return( 0 );
}
/**
* This function only returns zeros
*
* rng_state shall be NULL.
*/
static int rnd_zero_rand( void *rng_state, unsigned char *output, size_t len )
{
if( rng_state != NULL )
rng_state = NULL;
memset( output, 0, len );
return( 0 );
}
typedef struct
{
unsigned char *buf;
size_t length;
} rnd_buf_info;
/**
* This function returns random based on a buffer it receives.
*
* rng_state shall be a pointer to a rnd_buf_info structure.
*
* The number of bytes released from the buffer on each call to
* the random function is specified by per_call. (Can be between
* 1 and 4)
*
* After the buffer is empty it will return rand();
*/
static int rnd_buffer_rand( void *rng_state, unsigned char *output, size_t len )
{
rnd_buf_info *info = (rnd_buf_info *) rng_state;
size_t use_len;
if( rng_state == NULL )
return( rnd_std_rand( NULL, output, len ) );
use_len = len;
if( len > info->length )
use_len = info->length;
if( use_len )
{
memcpy( output, info->buf, use_len );
info->buf += use_len;
info->length -= use_len;
}
if( len - use_len > 0 )
return( rnd_std_rand( NULL, output + use_len, len - use_len ) );
return( 0 );
}
/**
* Info structure for the pseudo random function
*
* Key should be set at the start to a test-unique value.
* Do not forget endianness!
* State( v0, v1 ) should be set to zero.
*/
typedef struct
{
uint32_t key[16];
uint32_t v0, v1;
} rnd_pseudo_info;
/**
* This function returns random based on a pseudo random function.
* This means the results should be identical on all systems.
* Pseudo random is based on the XTEA encryption algorithm to
* generate pseudorandom.
*
* rng_state shall be a pointer to a rnd_pseudo_info structure.
*/
static int rnd_pseudo_rand( void *rng_state, unsigned char *output, size_t len )
{
rnd_pseudo_info *info = (rnd_pseudo_info *) rng_state;
uint32_t i, *k, sum, delta=0x9E3779B9;
unsigned char result[4];
if( rng_state == NULL )
return( rnd_std_rand( NULL, output, len ) );
k = info->key;
while( len > 0 )
{
size_t use_len = ( len > 4 ) ? 4 : len;
sum = 0;
for( i = 0; i < 32; i++ )
{
info->v0 += (((info->v1 << 4) ^ (info->v1 >> 5)) + info->v1) ^ (sum + k[sum & 3]);
sum += delta;
info->v1 += (((info->v0 << 4) ^ (info->v0 >> 5)) + info->v0) ^ (sum + k[(sum>>11) & 3]);
}
PUT_UINT32_BE( info->v0, result, 0 );
memcpy( output, result, use_len );
len -= use_len;
}
return( 0 );
}
int main() {
dhm_context ctx_cli;
unsigned char pub_cli[1000];
unsigned char sec_cli[1000];
size_t pub_cli_len = 0;
size_t sec_cli_len = 1000;
int x_size;
rnd_pseudo_info rnd_info;
memset( &ctx_cli, 0x00, sizeof( dhm_context ) );
memset( pub_cli, 0x00, 1000 );
memset( sec_cli, 0x00, 1000 );
memset( &rnd_info, 0x00, sizeof( rnd_pseudo_info ) );
assert( mpi_read_string( &ctx_cli.P, 10, "35963" ) == 0 ); // Prime of alice
assert( mpi_read_string( &ctx_cli.G, 10, "2" ) == 0 );
assert( mpi_read_string( &ctx_cli.GY, 10, "12371" ) == 0 ); // Public Key of alice
ctx_cli.len = mpi_size( &ctx_cli.P );
x_size = mpi_size( &ctx_cli.P );
pub_cli_len = x_size;
int r = dhm_make_public( &ctx_cli, x_size, pub_cli, pub_cli_len, &rnd_pseudo_rand, &rnd_info );
assert( r == 0 );
int i;
printf("Public Key of bob:");
for(i = 0; i < pub_cli_len; ++i)
printf("%02X", (unsigned char)pub_cli[i]);
printf("\n");
assert( dhm_calc_secret( &ctx_cli, sec_cli, &sec_cli_len ) == 0 );
printf("Shared Secret:");
for(i = 0; i < sec_cli_len; ++i)
printf("%02X", (unsigned char)sec_cli[i]);
printf("\n");
dhm_free( &ctx_cli );
return 0;
}
结果：
Public Key of bob:0D03
Shared Secret:3213
alice收到bob的Public Key
> s1 = alice.computeSecret('0D03', "hex", "hex");
'3213'